linux/kernel/seccomp.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * linux/kernel/seccomp.c
   4 *
   5 * Copyright 2004-2005  Andrea Arcangeli <andrea@cpushare.com>
   6 *
   7 * Copyright (C) 2012 Google, Inc.
   8 * Will Drewry <wad@chromium.org>
   9 *
  10 * This defines a simple but solid secure-computing facility.
  11 *
  12 * Mode 1 uses a fixed list of allowed system calls.
  13 * Mode 2 allows user-defined system call filters in the form
  14 *        of Berkeley Packet Filters/Linux Socket Filters.
  15 */
  16#define pr_fmt(fmt) "seccomp: " fmt
  17
  18#include <linux/refcount.h>
  19#include <linux/audit.h>
  20#include <linux/compat.h>
  21#include <linux/coredump.h>
  22#include <linux/kmemleak.h>
  23#include <linux/nospec.h>
  24#include <linux/prctl.h>
  25#include <linux/sched.h>
  26#include <linux/sched/task_stack.h>
  27#include <linux/seccomp.h>
  28#include <linux/slab.h>
  29#include <linux/syscalls.h>
  30#include <linux/sysctl.h>
  31
  32/* Not exposed in headers: strictly internal use only. */
  33#define SECCOMP_MODE_DEAD       (SECCOMP_MODE_FILTER + 1)
  34
  35#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
  36#include <asm/syscall.h>
  37#endif
  38
  39#ifdef CONFIG_SECCOMP_FILTER
  40#include <linux/file.h>
  41#include <linux/filter.h>
  42#include <linux/pid.h>
  43#include <linux/ptrace.h>
  44#include <linux/capability.h>
  45#include <linux/uaccess.h>
  46#include <linux/anon_inodes.h>
  47#include <linux/lockdep.h>
  48
  49/*
  50 * When SECCOMP_IOCTL_NOTIF_ID_VALID was first introduced, it had the
  51 * wrong direction flag in the ioctl number. This is the broken one,
  52 * which the kernel needs to keep supporting until all userspaces stop
  53 * using the wrong command number.
  54 */
  55#define SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR  SECCOMP_IOR(2, __u64)
  56
  57enum notify_state {
  58        SECCOMP_NOTIFY_INIT,
  59        SECCOMP_NOTIFY_SENT,
  60        SECCOMP_NOTIFY_REPLIED,
  61};
  62
  63struct seccomp_knotif {
  64        /* The struct pid of the task whose filter triggered the notification */
  65        struct task_struct *task;
  66
  67        /* The "cookie" for this request; this is unique for this filter. */
  68        u64 id;
  69
  70        /*
  71         * The seccomp data. This pointer is valid the entire time this
  72         * notification is active, since it comes from __seccomp_filter which
  73         * eclipses the entire lifecycle here.
  74         */
  75        const struct seccomp_data *data;
  76
  77        /*
  78         * Notification states. When SECCOMP_RET_USER_NOTIF is returned, a
  79         * struct seccomp_knotif is created and starts out in INIT. Once the
  80         * handler reads the notification off of an FD, it transitions to SENT.
  81         * If a signal is received the state transitions back to INIT and
  82         * another message is sent. When the userspace handler replies, state
  83         * transitions to REPLIED.
  84         */
  85        enum notify_state state;
  86
  87        /* The return values, only valid when in SECCOMP_NOTIFY_REPLIED */
  88        int error;
  89        long val;
  90        u32 flags;
  91
  92        /*
  93         * Signals when this has changed states, such as the listener
  94         * dying, a new seccomp addfd message, or changing to REPLIED
  95         */
  96        struct completion ready;
  97
  98        struct list_head list;
  99
 100        /* outstanding addfd requests */
 101        struct list_head addfd;
 102};
 103
 104/**
 105 * struct seccomp_kaddfd - container for seccomp_addfd ioctl messages
 106 *
 107 * @file: A reference to the file to install in the other task
 108 * @fd: The fd number to install it at. If the fd number is -1, it means the
 109 *      installing process should allocate the fd as normal.
 110 * @flags: The flags for the new file descriptor. At the moment, only O_CLOEXEC
 111 *         is allowed.
 112 * @ioctl_flags: The flags used for the seccomp_addfd ioctl.
 113 * @ret: The return value of the installing process. It is set to the fd num
 114 *       upon success (>= 0).
 115 * @completion: Indicates that the installing process has completed fd
 116 *              installation, or gone away (either due to successful
 117 *              reply, or signal)
 118 *
 119 */
 120struct seccomp_kaddfd {
 121        struct file *file;
 122        int fd;
 123        unsigned int flags;
 124        __u32 ioctl_flags;
 125
 126        union {
 127                bool setfd;
 128                /* To only be set on reply */
 129                int ret;
 130        };
 131        struct completion completion;
 132        struct list_head list;
 133};
 134
 135/**
 136 * struct notification - container for seccomp userspace notifications. Since
 137 * most seccomp filters will not have notification listeners attached and this
 138 * structure is fairly large, we store the notification-specific stuff in a
 139 * separate structure.
 140 *
 141 * @request: A semaphore that users of this notification can wait on for
 142 *           changes. Actual reads and writes are still controlled with
 143 *           filter->notify_lock.
 144 * @next_id: The id of the next request.
 145 * @notifications: A list of struct seccomp_knotif elements.
 146 */
 147struct notification {
 148        struct semaphore request;
 149        u64 next_id;
 150        struct list_head notifications;
 151};
 152
 153#ifdef SECCOMP_ARCH_NATIVE
 154/**
 155 * struct action_cache - per-filter cache of seccomp actions per
 156 * arch/syscall pair
 157 *
 158 * @allow_native: A bitmap where each bit represents whether the
 159 *                filter will always allow the syscall, for the
 160 *                native architecture.
 161 * @allow_compat: A bitmap where each bit represents whether the
 162 *                filter will always allow the syscall, for the
 163 *                compat architecture.
 164 */
 165struct action_cache {
 166        DECLARE_BITMAP(allow_native, SECCOMP_ARCH_NATIVE_NR);
 167#ifdef SECCOMP_ARCH_COMPAT
 168        DECLARE_BITMAP(allow_compat, SECCOMP_ARCH_COMPAT_NR);
 169#endif
 170};
 171#else
 172struct action_cache { };
 173
 174static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilter,
 175                                             const struct seccomp_data *sd)
 176{
 177        return false;
 178}
 179
 180static inline void seccomp_cache_prepare(struct seccomp_filter *sfilter)
 181{
 182}
 183#endif /* SECCOMP_ARCH_NATIVE */
 184
 185/**
 186 * struct seccomp_filter - container for seccomp BPF programs
 187 *
 188 * @refs: Reference count to manage the object lifetime.
 189 *        A filter's reference count is incremented for each directly
 190 *        attached task, once for the dependent filter, and if
 191 *        requested for the user notifier. When @refs reaches zero,
 192 *        the filter can be freed.
 193 * @users: A filter's @users count is incremented for each directly
 194 *         attached task (filter installation, fork(), thread_sync),
 195 *         and once for the dependent filter (tracked in filter->prev).
 196 *         When it reaches zero it indicates that no direct or indirect
 197 *         users of that filter exist. No new tasks can get associated with
 198 *         this filter after reaching 0. The @users count is always smaller
 199 *         or equal to @refs. Hence, reaching 0 for @users does not mean
 200 *         the filter can be freed.
 201 * @cache: cache of arch/syscall mappings to actions
 202 * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
 203 * @wait_killable_recv: Put notifying process in killable state once the
 204 *                      notification is received by the userspace listener.
 205 * @prev: points to a previously installed, or inherited, filter
 206 * @prog: the BPF program to evaluate
 207 * @notif: the struct that holds all notification related information
 208 * @notify_lock: A lock for all notification-related accesses.
 209 * @wqh: A wait queue for poll if a notifier is in use.
 210 *
 211 * seccomp_filter objects are organized in a tree linked via the @prev
 212 * pointer.  For any task, it appears to be a singly-linked list starting
 213 * with current->seccomp.filter, the most recently attached or inherited filter.
 214 * However, multiple filters may share a @prev node, by way of fork(), which
 215 * results in a unidirectional tree existing in memory.  This is similar to
 216 * how namespaces work.
 217 *
 218 * seccomp_filter objects should never be modified after being attached
 219 * to a task_struct (other than @refs).
 220 */
 221struct seccomp_filter {
 222        refcount_t refs;
 223        refcount_t users;
 224        bool log;
 225        bool wait_killable_recv;
 226        struct action_cache cache;
 227        struct seccomp_filter *prev;
 228        struct bpf_prog *prog;
 229        struct notification *notif;
 230        struct mutex notify_lock;
 231        wait_queue_head_t wqh;
 232};
 233
 234/* Limit any path through the tree to 256KB worth of instructions. */
 235#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
 236
 237/*
 238 * Endianness is explicitly ignored and left for BPF program authors to manage
 239 * as per the specific architecture.
 240 */
 241static void populate_seccomp_data(struct seccomp_data *sd)
 242{
 243        /*
 244         * Instead of using current_pt_reg(), we're already doing the work
 245         * to safely fetch "current", so just use "task" everywhere below.
 246         */
 247        struct task_struct *task = current;
 248        struct pt_regs *regs = task_pt_regs(task);
 249        unsigned long args[6];
 250
 251        sd->nr = syscall_get_nr(task, regs);
 252        sd->arch = syscall_get_arch(task);
 253        syscall_get_arguments(task, regs, args);
 254        sd->args[0] = args[0];
 255        sd->args[1] = args[1];
 256        sd->args[2] = args[2];
 257        sd->args[3] = args[3];
 258        sd->args[4] = args[4];
 259        sd->args[5] = args[5];
 260        sd->instruction_pointer = KSTK_EIP(task);
 261}
 262
 263/**
 264 *      seccomp_check_filter - verify seccomp filter code
 265 *      @filter: filter to verify
 266 *      @flen: length of filter
 267 *
 268 * Takes a previously checked filter (by bpf_check_classic) and
 269 * redirects all filter code that loads struct sk_buff data
 270 * and related data through seccomp_bpf_load.  It also
 271 * enforces length and alignment checking of those loads.
 272 *
 273 * Returns 0 if the rule set is legal or -EINVAL if not.
 274 */
 275static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
 276{
 277        int pc;
 278        for (pc = 0; pc < flen; pc++) {
 279                struct sock_filter *ftest = &filter[pc];
 280                u16 code = ftest->code;
 281                u32 k = ftest->k;
 282
 283                switch (code) {
 284                case BPF_LD | BPF_W | BPF_ABS:
 285                        ftest->code = BPF_LDX | BPF_W | BPF_ABS;
 286                        /* 32-bit aligned and not out of bounds. */
 287                        if (k >= sizeof(struct seccomp_data) || k & 3)
 288                                return -EINVAL;
 289                        continue;
 290                case BPF_LD | BPF_W | BPF_LEN:
 291                        ftest->code = BPF_LD | BPF_IMM;
 292                        ftest->k = sizeof(struct seccomp_data);
 293                        continue;
 294                case BPF_LDX | BPF_W | BPF_LEN:
 295                        ftest->code = BPF_LDX | BPF_IMM;
 296                        ftest->k = sizeof(struct seccomp_data);
 297                        continue;
 298                /* Explicitly include allowed calls. */
 299                case BPF_RET | BPF_K:
 300                case BPF_RET | BPF_A:
 301                case BPF_ALU | BPF_ADD | BPF_K:
 302                case BPF_ALU | BPF_ADD | BPF_X:
 303                case BPF_ALU | BPF_SUB | BPF_K:
 304                case BPF_ALU | BPF_SUB | BPF_X:
 305                case BPF_ALU | BPF_MUL | BPF_K:
 306                case BPF_ALU | BPF_MUL | BPF_X:
 307                case BPF_ALU | BPF_DIV | BPF_K:
 308                case BPF_ALU | BPF_DIV | BPF_X:
 309                case BPF_ALU | BPF_AND | BPF_K:
 310                case BPF_ALU | BPF_AND | BPF_X:
 311                case BPF_ALU | BPF_OR | BPF_K:
 312                case BPF_ALU | BPF_OR | BPF_X:
 313                case BPF_ALU | BPF_XOR | BPF_K:
 314                case BPF_ALU | BPF_XOR | BPF_X:
 315                case BPF_ALU | BPF_LSH | BPF_K:
 316                case BPF_ALU | BPF_LSH | BPF_X:
 317                case BPF_ALU | BPF_RSH | BPF_K:
 318                case BPF_ALU | BPF_RSH | BPF_X:
 319                case BPF_ALU | BPF_NEG:
 320                case BPF_LD | BPF_IMM:
 321                case BPF_LDX | BPF_IMM:
 322                case BPF_MISC | BPF_TAX:
 323                case BPF_MISC | BPF_TXA:
 324                case BPF_LD | BPF_MEM:
 325                case BPF_LDX | BPF_MEM:
 326                case BPF_ST:
 327                case BPF_STX:
 328                case BPF_JMP | BPF_JA:
 329                case BPF_JMP | BPF_JEQ | BPF_K:
 330                case BPF_JMP | BPF_JEQ | BPF_X:
 331                case BPF_JMP | BPF_JGE | BPF_K:
 332                case BPF_JMP | BPF_JGE | BPF_X:
 333                case BPF_JMP | BPF_JGT | BPF_K:
 334                case BPF_JMP | BPF_JGT | BPF_X:
 335                case BPF_JMP | BPF_JSET | BPF_K:
 336                case BPF_JMP | BPF_JSET | BPF_X:
 337                        continue;
 338                default:
 339                        return -EINVAL;
 340                }
 341        }
 342        return 0;
 343}
 344
 345#ifdef SECCOMP_ARCH_NATIVE
 346static inline bool seccomp_cache_check_allow_bitmap(const void *bitmap,
 347                                                    size_t bitmap_size,
 348                                                    int syscall_nr)
 349{
 350        if (unlikely(syscall_nr < 0 || syscall_nr >= bitmap_size))
 351                return false;
 352        syscall_nr = array_index_nospec(syscall_nr, bitmap_size);
 353
 354        return test_bit(syscall_nr, bitmap);
 355}
 356
 357/**
 358 * seccomp_cache_check_allow - lookup seccomp cache
 359 * @sfilter: The seccomp filter
 360 * @sd: The seccomp data to lookup the cache with
 361 *
 362 * Returns true if the seccomp_data is cached and allowed.
 363 */
 364static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilter,
 365                                             const struct seccomp_data *sd)
 366{
 367        int syscall_nr = sd->nr;
 368        const struct action_cache *cache = &sfilter->cache;
 369
 370#ifndef SECCOMP_ARCH_COMPAT
 371        /* A native-only architecture doesn't need to check sd->arch. */
 372        return seccomp_cache_check_allow_bitmap(cache->allow_native,
 373                                                SECCOMP_ARCH_NATIVE_NR,
 374                                                syscall_nr);
 375#else
 376        if (likely(sd->arch == SECCOMP_ARCH_NATIVE))
 377                return seccomp_cache_check_allow_bitmap(cache->allow_native,
 378                                                        SECCOMP_ARCH_NATIVE_NR,
 379                                                        syscall_nr);
 380        if (likely(sd->arch == SECCOMP_ARCH_COMPAT))
 381                return seccomp_cache_check_allow_bitmap(cache->allow_compat,
 382                                                        SECCOMP_ARCH_COMPAT_NR,
 383                                                        syscall_nr);
 384#endif /* SECCOMP_ARCH_COMPAT */
 385
 386        WARN_ON_ONCE(true);
 387        return false;
 388}
 389#endif /* SECCOMP_ARCH_NATIVE */
 390
 391/**
 392 * seccomp_run_filters - evaluates all seccomp filters against @sd
 393 * @sd: optional seccomp data to be passed to filters
 394 * @match: stores struct seccomp_filter that resulted in the return value,
 395 *         unless filter returned SECCOMP_RET_ALLOW, in which case it will
 396 *         be unchanged.
 397 *
 398 * Returns valid seccomp BPF response codes.
 399 */
 400#define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL)))
 401static u32 seccomp_run_filters(const struct seccomp_data *sd,
 402                               struct seccomp_filter **match)
 403{
 404        u32 ret = SECCOMP_RET_ALLOW;
 405        /* Make sure cross-thread synced filter points somewhere sane. */
 406        struct seccomp_filter *f =
 407                        READ_ONCE(current->seccomp.filter);
 408
 409        /* Ensure unexpected behavior doesn't result in failing open. */
 410        if (WARN_ON(f == NULL))
 411                return SECCOMP_RET_KILL_PROCESS;
 412
 413        if (seccomp_cache_check_allow(f, sd))
 414                return SECCOMP_RET_ALLOW;
 415
 416        /*
 417         * All filters in the list are evaluated and the lowest BPF return
 418         * value always takes priority (ignoring the DATA).
 419         */
 420        for (; f; f = f->prev) {
 421                u32 cur_ret = bpf_prog_run_pin_on_cpu(f->prog, sd);
 422
 423                if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) {
 424                        ret = cur_ret;
 425                        *match = f;
 426                }
 427        }
 428        return ret;
 429}
 430#endif /* CONFIG_SECCOMP_FILTER */
 431
 432static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
 433{
 434        assert_spin_locked(&current->sighand->siglock);
 435
 436        if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
 437                return false;
 438
 439        return true;
 440}
 441
 442void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { }
 443
 444static inline void seccomp_assign_mode(struct task_struct *task,
 445                                       unsigned long seccomp_mode,
 446                                       unsigned long flags)
 447{
 448        assert_spin_locked(&task->sighand->siglock);
 449
 450        task->seccomp.mode = seccomp_mode;
 451        /*
 452         * Make sure SYSCALL_WORK_SECCOMP cannot be set before the mode (and
 453         * filter) is set.
 454         */
 455        smp_mb__before_atomic();
 456        /* Assume default seccomp processes want spec flaw mitigation. */
 457        if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0)
 458                arch_seccomp_spec_mitigate(task);
 459        set_task_syscall_work(task, SECCOMP);
 460}
 461
 462#ifdef CONFIG_SECCOMP_FILTER
 463/* Returns 1 if the parent is an ancestor of the child. */
 464static int is_ancestor(struct seccomp_filter *parent,
 465                       struct seccomp_filter *child)
 466{
 467        /* NULL is the root ancestor. */
 468        if (parent == NULL)
 469                return 1;
 470        for (; child; child = child->prev)
 471                if (child == parent)
 472                        return 1;
 473        return 0;
 474}
 475
 476/**
 477 * seccomp_can_sync_threads: checks if all threads can be synchronized
 478 *
 479 * Expects sighand and cred_guard_mutex locks to be held.
 480 *
 481 * Returns 0 on success, -ve on error, or the pid of a thread which was
 482 * either not in the correct seccomp mode or did not have an ancestral
 483 * seccomp filter.
 484 */
 485static inline pid_t seccomp_can_sync_threads(void)
 486{
 487        struct task_struct *thread, *caller;
 488
 489        BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
 490        assert_spin_locked(&current->sighand->siglock);
 491
 492        /* Validate all threads being eligible for synchronization. */
 493        caller = current;
 494        for_each_thread(caller, thread) {
 495                pid_t failed;
 496
 497                /* Skip current, since it is initiating the sync. */
 498                if (thread == caller)
 499                        continue;
 500
 501                if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
 502                    (thread->seccomp.mode == SECCOMP_MODE_FILTER &&
 503                     is_ancestor(thread->seccomp.filter,
 504                                 caller->seccomp.filter)))
 505                        continue;
 506
 507                /* Return the first thread that cannot be synchronized. */
 508                failed = task_pid_vnr(thread);
 509                /* If the pid cannot be resolved, then return -ESRCH */
 510                if (WARN_ON(failed == 0))
 511                        failed = -ESRCH;
 512                return failed;
 513        }
 514
 515        return 0;
 516}
 517
 518static inline void seccomp_filter_free(struct seccomp_filter *filter)
 519{
 520        if (filter) {
 521                bpf_prog_destroy(filter->prog);
 522                kfree(filter);
 523        }
 524}
 525
 526static void __seccomp_filter_orphan(struct seccomp_filter *orig)
 527{
 528        while (orig && refcount_dec_and_test(&orig->users)) {
 529                if (waitqueue_active(&orig->wqh))
 530                        wake_up_poll(&orig->wqh, EPOLLHUP);
 531                orig = orig->prev;
 532        }
 533}
 534
 535static void __put_seccomp_filter(struct seccomp_filter *orig)
 536{
 537        /* Clean up single-reference branches iteratively. */
 538        while (orig && refcount_dec_and_test(&orig->refs)) {
 539                struct seccomp_filter *freeme = orig;
 540                orig = orig->prev;
 541                seccomp_filter_free(freeme);
 542        }
 543}
 544
 545static void __seccomp_filter_release(struct seccomp_filter *orig)
 546{
 547        /* Notify about any unused filters in the task's former filter tree. */
 548        __seccomp_filter_orphan(orig);
 549        /* Finally drop all references to the task's former tree. */
 550        __put_seccomp_filter(orig);
 551}
 552
 553/**
 554 * seccomp_filter_release - Detach the task from its filter tree,
 555 *                          drop its reference count, and notify
 556 *                          about unused filters
 557 *
 558 * This function should only be called when the task is exiting as
 559 * it detaches it from its filter tree. As such, READ_ONCE() and
 560 * barriers are not needed here, as would normally be needed.
 561 */
 562void seccomp_filter_release(struct task_struct *tsk)
 563{
 564        struct seccomp_filter *orig = tsk->seccomp.filter;
 565
 566        /* We are effectively holding the siglock by not having any sighand. */
 567        WARN_ON(tsk->sighand != NULL);
 568
 569        /* Detach task from its filter tree. */
 570        tsk->seccomp.filter = NULL;
 571        __seccomp_filter_release(orig);
 572}
 573
 574/**
 575 * seccomp_sync_threads: sets all threads to use current's filter
 576 *
 577 * Expects sighand and cred_guard_mutex locks to be held, and for
 578 * seccomp_can_sync_threads() to have returned success already
 579 * without dropping the locks.
 580 *
 581 */
 582static inline void seccomp_sync_threads(unsigned long flags)
 583{
 584        struct task_struct *thread, *caller;
 585
 586        BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
 587        assert_spin_locked(&current->sighand->siglock);
 588
 589        /* Synchronize all threads. */
 590        caller = current;
 591        for_each_thread(caller, thread) {
 592                /* Skip current, since it needs no changes. */
 593                if (thread == caller)
 594                        continue;
 595
 596                /* Get a task reference for the new leaf node. */
 597                get_seccomp_filter(caller);
 598
 599                /*
 600                 * Drop the task reference to the shared ancestor since
 601                 * current's path will hold a reference.  (This also
 602                 * allows a put before the assignment.)
 603                 */
 604                __seccomp_filter_release(thread->seccomp.filter);
 605
 606                /* Make our new filter tree visible. */
 607                smp_store_release(&thread->seccomp.filter,
 608                                  caller->seccomp.filter);
 609                atomic_set(&thread->seccomp.filter_count,
 610                           atomic_read(&caller->seccomp.filter_count));
 611
 612                /*
 613                 * Don't let an unprivileged task work around
 614                 * the no_new_privs restriction by creating
 615                 * a thread that sets it up, enters seccomp,
 616                 * then dies.
 617                 */
 618                if (task_no_new_privs(caller))
 619                        task_set_no_new_privs(thread);
 620
 621                /*
 622                 * Opt the other thread into seccomp if needed.
 623                 * As threads are considered to be trust-realm
 624                 * equivalent (see ptrace_may_access), it is safe to
 625                 * allow one thread to transition the other.
 626                 */
 627                if (thread->seccomp.mode == SECCOMP_MODE_DISABLED)
 628                        seccomp_assign_mode(thread, SECCOMP_MODE_FILTER,
 629                                            flags);
 630        }
 631}
 632
 633/**
 634 * seccomp_prepare_filter: Prepares a seccomp filter for use.
 635 * @fprog: BPF program to install
 636 *
 637 * Returns filter on success or an ERR_PTR on failure.
 638 */
 639static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
 640{
 641        struct seccomp_filter *sfilter;
 642        int ret;
 643        const bool save_orig =
 644#if defined(CONFIG_CHECKPOINT_RESTORE) || defined(SECCOMP_ARCH_NATIVE)
 645                true;
 646#else
 647                false;
 648#endif
 649
 650        if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
 651                return ERR_PTR(-EINVAL);
 652
 653        BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
 654
 655        /*
 656         * Installing a seccomp filter requires that the task has
 657         * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
 658         * This avoids scenarios where unprivileged tasks can affect the
 659         * behavior of privileged children.
 660         */
 661        if (!task_no_new_privs(current) &&
 662                        !ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN))
 663                return ERR_PTR(-EACCES);
 664
 665        /* Allocate a new seccomp_filter */
 666        sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
 667        if (!sfilter)
 668                return ERR_PTR(-ENOMEM);
 669
 670        mutex_init(&sfilter->notify_lock);
 671        ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
 672                                        seccomp_check_filter, save_orig);
 673        if (ret < 0) {
 674                kfree(sfilter);
 675                return ERR_PTR(ret);
 676        }
 677
 678        refcount_set(&sfilter->refs, 1);
 679        refcount_set(&sfilter->users, 1);
 680        init_waitqueue_head(&sfilter->wqh);
 681
 682        return sfilter;
 683}
 684
 685/**
 686 * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
 687 * @user_filter: pointer to the user data containing a sock_fprog.
 688 *
 689 * Returns 0 on success and non-zero otherwise.
 690 */
 691static struct seccomp_filter *
 692seccomp_prepare_user_filter(const char __user *user_filter)
 693{
 694        struct sock_fprog fprog;
 695        struct seccomp_filter *filter = ERR_PTR(-EFAULT);
 696
 697#ifdef CONFIG_COMPAT
 698        if (in_compat_syscall()) {
 699                struct compat_sock_fprog fprog32;
 700                if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
 701                        goto out;
 702                fprog.len = fprog32.len;
 703                fprog.filter = compat_ptr(fprog32.filter);
 704        } else /* falls through to the if below. */
 705#endif
 706        if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
 707                goto out;
 708        filter = seccomp_prepare_filter(&fprog);
 709out:
 710        return filter;
 711}
 712
 713#ifdef SECCOMP_ARCH_NATIVE
 714/**
 715 * seccomp_is_const_allow - check if filter is constant allow with given data
 716 * @fprog: The BPF programs
 717 * @sd: The seccomp data to check against, only syscall number and arch
 718 *      number are considered constant.
 719 */
 720static bool seccomp_is_const_allow(struct sock_fprog_kern *fprog,
 721                                   struct seccomp_data *sd)
 722{
 723        unsigned int reg_value = 0;
 724        unsigned int pc;
 725        bool op_res;
 726
 727        if (WARN_ON_ONCE(!fprog))
 728                return false;
 729
 730        for (pc = 0; pc < fprog->len; pc++) {
 731                struct sock_filter *insn = &fprog->filter[pc];
 732                u16 code = insn->code;
 733                u32 k = insn->k;
 734
 735                switch (code) {
 736                case BPF_LD | BPF_W | BPF_ABS:
 737                        switch (k) {
 738                        case offsetof(struct seccomp_data, nr):
 739                                reg_value = sd->nr;
 740                                break;
 741                        case offsetof(struct seccomp_data, arch):
 742                                reg_value = sd->arch;
 743                                break;
 744                        default:
 745                                /* can't optimize (non-constant value load) */
 746                                return false;
 747                        }
 748                        break;
 749                case BPF_RET | BPF_K:
 750                        /* reached return with constant values only, check allow */
 751                        return k == SECCOMP_RET_ALLOW;
 752                case BPF_JMP | BPF_JA:
 753                        pc += insn->k;
 754                        break;
 755                case BPF_JMP | BPF_JEQ | BPF_K:
 756                case BPF_JMP | BPF_JGE | BPF_K:
 757                case BPF_JMP | BPF_JGT | BPF_K:
 758                case BPF_JMP | BPF_JSET | BPF_K:
 759                        switch (BPF_OP(code)) {
 760                        case BPF_JEQ:
 761                                op_res = reg_value == k;
 762                                break;
 763                        case BPF_JGE:
 764                                op_res = reg_value >= k;
 765                                break;
 766                        case BPF_JGT:
 767                                op_res = reg_value > k;
 768                                break;
 769                        case BPF_JSET:
 770                                op_res = !!(reg_value & k);
 771                                break;
 772                        default:
 773                                /* can't optimize (unknown jump) */
 774                                return false;
 775                        }
 776
 777                        pc += op_res ? insn->jt : insn->jf;
 778                        break;
 779                case BPF_ALU | BPF_AND | BPF_K:
 780                        reg_value &= k;
 781                        break;
 782                default:
 783                        /* can't optimize (unknown insn) */
 784                        return false;
 785                }
 786        }
 787
 788        /* ran off the end of the filter?! */
 789        WARN_ON(1);
 790        return false;
 791}
 792
 793static void seccomp_cache_prepare_bitmap(struct seccomp_filter *sfilter,
 794                                         void *bitmap, const void *bitmap_prev,
 795                                         size_t bitmap_size, int arch)
 796{
 797        struct sock_fprog_kern *fprog = sfilter->prog->orig_prog;
 798        struct seccomp_data sd;
 799        int nr;
 800
 801        if (bitmap_prev) {
 802                /* The new filter must be as restrictive as the last. */
 803                bitmap_copy(bitmap, bitmap_prev, bitmap_size);
 804        } else {
 805                /* Before any filters, all syscalls are always allowed. */
 806                bitmap_fill(bitmap, bitmap_size);
 807        }
 808
 809        for (nr = 0; nr < bitmap_size; nr++) {
 810                /* No bitmap change: not a cacheable action. */
 811                if (!test_bit(nr, bitmap))
 812                        continue;
 813
 814                sd.nr = nr;
 815                sd.arch = arch;
 816
 817                /* No bitmap change: continue to always allow. */
 818                if (seccomp_is_const_allow(fprog, &sd))
 819                        continue;
 820
 821                /*
 822                 * Not a cacheable action: always run filters.
 823                 * atomic clear_bit() not needed, filter not visible yet.
 824                 */
 825                __clear_bit(nr, bitmap);
 826        }
 827}
 828
 829/**
 830 * seccomp_cache_prepare - emulate the filter to find cacheable syscalls
 831 * @sfilter: The seccomp filter
 832 *
 833 * Returns 0 if successful or -errno if error occurred.
 834 */
 835static void seccomp_cache_prepare(struct seccomp_filter *sfilter)
 836{
 837        struct action_cache *cache = &sfilter->cache;
 838        const struct action_cache *cache_prev =
 839                sfilter->prev ? &sfilter->prev->cache : NULL;
 840
 841        seccomp_cache_prepare_bitmap(sfilter, cache->allow_native,
 842                                     cache_prev ? cache_prev->allow_native : NULL,
 843                                     SECCOMP_ARCH_NATIVE_NR,
 844                                     SECCOMP_ARCH_NATIVE);
 845
 846#ifdef SECCOMP_ARCH_COMPAT
 847        seccomp_cache_prepare_bitmap(sfilter, cache->allow_compat,
 848                                     cache_prev ? cache_prev->allow_compat : NULL,
 849                                     SECCOMP_ARCH_COMPAT_NR,
 850                                     SECCOMP_ARCH_COMPAT);
 851#endif /* SECCOMP_ARCH_COMPAT */
 852}
 853#endif /* SECCOMP_ARCH_NATIVE */
 854
 855/**
 856 * seccomp_attach_filter: validate and attach filter
 857 * @flags:  flags to change filter behavior
 858 * @filter: seccomp filter to add to the current process
 859 *
 860 * Caller must be holding current->sighand->siglock lock.
 861 *
 862 * Returns 0 on success, -ve on error, or
 863 *   - in TSYNC mode: the pid of a thread which was either not in the correct
 864 *     seccomp mode or did not have an ancestral seccomp filter
 865 *   - in NEW_LISTENER mode: the fd of the new listener
 866 */
 867static long seccomp_attach_filter(unsigned int flags,
 868                                  struct seccomp_filter *filter)
 869{
 870        unsigned long total_insns;
 871        struct seccomp_filter *walker;
 872
 873        assert_spin_locked(&current->sighand->siglock);
 874
 875        /* Validate resulting filter length. */
 876        total_insns = filter->prog->len;
 877        for (walker = current->seccomp.filter; walker; walker = walker->prev)
 878                total_insns += walker->prog->len + 4;  /* 4 instr penalty */
 879        if (total_insns > MAX_INSNS_PER_PATH)
 880                return -ENOMEM;
 881
 882        /* If thread sync has been requested, check that it is possible. */
 883        if (flags & SECCOMP_FILTER_FLAG_TSYNC) {
 884                int ret;
 885
 886                ret = seccomp_can_sync_threads();
 887                if (ret) {
 888                        if (flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH)
 889                                return -ESRCH;
 890                        else
 891                                return ret;
 892                }
 893        }
 894
 895        /* Set log flag, if present. */
 896        if (flags & SECCOMP_FILTER_FLAG_LOG)
 897                filter->log = true;
 898
 899        /* Set wait killable flag, if present. */
 900        if (flags & SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV)
 901                filter->wait_killable_recv = true;
 902
 903        /*
 904         * If there is an existing filter, make it the prev and don't drop its
 905         * task reference.
 906         */
 907        filter->prev = current->seccomp.filter;
 908        seccomp_cache_prepare(filter);
 909        current->seccomp.filter = filter;
 910        atomic_inc(&current->seccomp.filter_count);
 911
 912        /* Now that the new filter is in place, synchronize to all threads. */
 913        if (flags & SECCOMP_FILTER_FLAG_TSYNC)
 914                seccomp_sync_threads(flags);
 915
 916        return 0;
 917}
 918
 919static void __get_seccomp_filter(struct seccomp_filter *filter)
 920{
 921        refcount_inc(&filter->refs);
 922}
 923
 924/* get_seccomp_filter - increments the reference count of the filter on @tsk */
 925void get_seccomp_filter(struct task_struct *tsk)
 926{
 927        struct seccomp_filter *orig = tsk->seccomp.filter;
 928        if (!orig)
 929                return;
 930        __get_seccomp_filter(orig);
 931        refcount_inc(&orig->users);
 932}
 933
 934#endif  /* CONFIG_SECCOMP_FILTER */
 935
 936/* For use with seccomp_actions_logged */
 937#define SECCOMP_LOG_KILL_PROCESS        (1 << 0)
 938#define SECCOMP_LOG_KILL_THREAD         (1 << 1)
 939#define SECCOMP_LOG_TRAP                (1 << 2)
 940#define SECCOMP_LOG_ERRNO               (1 << 3)
 941#define SECCOMP_LOG_TRACE               (1 << 4)
 942#define SECCOMP_LOG_LOG                 (1 << 5)
 943#define SECCOMP_LOG_ALLOW               (1 << 6)
 944#define SECCOMP_LOG_USER_NOTIF          (1 << 7)
 945
 946static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS |
 947                                    SECCOMP_LOG_KILL_THREAD  |
 948                                    SECCOMP_LOG_TRAP  |
 949                                    SECCOMP_LOG_ERRNO |
 950                                    SECCOMP_LOG_USER_NOTIF |
 951                                    SECCOMP_LOG_TRACE |
 952                                    SECCOMP_LOG_LOG;
 953
 954static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
 955                               bool requested)
 956{
 957        bool log = false;
 958
 959        switch (action) {
 960        case SECCOMP_RET_ALLOW:
 961                break;
 962        case SECCOMP_RET_TRAP:
 963                log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP;
 964                break;
 965        case SECCOMP_RET_ERRNO:
 966                log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO;
 967                break;
 968        case SECCOMP_RET_TRACE:
 969                log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
 970                break;
 971        case SECCOMP_RET_USER_NOTIF:
 972                log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF;
 973                break;
 974        case SECCOMP_RET_LOG:
 975                log = seccomp_actions_logged & SECCOMP_LOG_LOG;
 976                break;
 977        case SECCOMP_RET_KILL_THREAD:
 978                log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD;
 979                break;
 980        case SECCOMP_RET_KILL_PROCESS:
 981        default:
 982                log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS;
 983        }
 984
 985        /*
 986         * Emit an audit message when the action is RET_KILL_*, RET_LOG, or the
 987         * FILTER_FLAG_LOG bit was set. The admin has the ability to silence
 988         * any action from being logged by removing the action name from the
 989         * seccomp_actions_logged sysctl.
 990         */
 991        if (!log)
 992                return;
 993
 994        audit_seccomp(syscall, signr, action);
 995}
 996
 997/*
 998 * Secure computing mode 1 allows only read/write/exit/sigreturn.
 999 * To be fully secure this must be combined with rlimit
1000 * to limit the stack allocations too.
1001 */
1002static const int mode1_syscalls[] = {
1003        __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
1004        -1, /* negative terminated */
1005};
1006
1007static void __secure_computing_strict(int this_syscall)
1008{
1009        const int *allowed_syscalls = mode1_syscalls;
1010#ifdef CONFIG_COMPAT
1011        if (in_compat_syscall())
1012                allowed_syscalls = get_compat_mode1_syscalls();
1013#endif
1014        do {
1015                if (*allowed_syscalls == this_syscall)
1016                        return;
1017        } while (*++allowed_syscalls != -1);
1018
1019#ifdef SECCOMP_DEBUG
1020        dump_stack();
1021#endif
1022        current->seccomp.mode = SECCOMP_MODE_DEAD;
1023        seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true);
1024        do_exit(SIGKILL);
1025}
1026
1027#ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
1028void secure_computing_strict(int this_syscall)
1029{
1030        int mode = current->seccomp.mode;
1031
1032        if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
1033            unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
1034                return;
1035
1036        if (mode == SECCOMP_MODE_DISABLED)
1037                return;
1038        else if (mode == SECCOMP_MODE_STRICT)
1039                __secure_computing_strict(this_syscall);
1040        else
1041                BUG();
1042}
1043#else
1044
1045#ifdef CONFIG_SECCOMP_FILTER
1046static u64 seccomp_next_notify_id(struct seccomp_filter *filter)
1047{
1048        /*
1049         * Note: overflow is ok here, the id just needs to be unique per
1050         * filter.
1051         */
1052        lockdep_assert_held(&filter->notify_lock);
1053        return filter->notif->next_id++;
1054}
1055
1056static void seccomp_handle_addfd(struct seccomp_kaddfd *addfd, struct seccomp_knotif *n)
1057{
1058        int fd;
1059
1060        /*
1061         * Remove the notification, and reset the list pointers, indicating
1062         * that it has been handled.
1063         */
1064        list_del_init(&addfd->list);
1065        if (!addfd->setfd)
1066                fd = receive_fd(addfd->file, addfd->flags);
1067        else
1068                fd = receive_fd_replace(addfd->fd, addfd->file, addfd->flags);
1069        addfd->ret = fd;
1070
1071        if (addfd->ioctl_flags & SECCOMP_ADDFD_FLAG_SEND) {
1072                /* If we fail reset and return an error to the notifier */
1073                if (fd < 0) {
1074                        n->state = SECCOMP_NOTIFY_SENT;
1075                } else {
1076                        /* Return the FD we just added */
1077                        n->flags = 0;
1078                        n->error = 0;
1079                        n->val = fd;
1080                }
1081        }
1082
1083        /*
1084         * Mark the notification as completed. From this point, addfd mem
1085         * might be invalidated and we can't safely read it anymore.
1086         */
1087        complete(&addfd->completion);
1088}
1089
1090static bool should_sleep_killable(struct seccomp_filter *match,
1091                                  struct seccomp_knotif *n)
1092{
1093        return match->wait_killable_recv && n->state == SECCOMP_NOTIFY_SENT;
1094}
1095
1096static int seccomp_do_user_notification(int this_syscall,
1097                                        struct seccomp_filter *match,
1098                                        const struct seccomp_data *sd)
1099{
1100        int err;
1101        u32 flags = 0;
1102        long ret = 0;
1103        struct seccomp_knotif n = {};
1104        struct seccomp_kaddfd *addfd, *tmp;
1105
1106        mutex_lock(&match->notify_lock);
1107        err = -ENOSYS;
1108        if (!match->notif)
1109                goto out;
1110
1111        n.task = current;
1112        n.state = SECCOMP_NOTIFY_INIT;
1113        n.data = sd;
1114        n.id = seccomp_next_notify_id(match);
1115        init_completion(&n.ready);
1116        list_add_tail(&n.list, &match->notif->notifications);
1117        INIT_LIST_HEAD(&n.addfd);
1118
1119        up(&match->notif->request);
1120        wake_up_poll(&match->wqh, EPOLLIN | EPOLLRDNORM);
1121
1122        /*
1123         * This is where we wait for a reply from userspace.
1124         */
1125        do {
1126                bool wait_killable = should_sleep_killable(match, &n);
1127
1128                mutex_unlock(&match->notify_lock);
1129                if (wait_killable)
1130                        err = wait_for_completion_killable(&n.ready);
1131                else
1132                        err = wait_for_completion_interruptible(&n.ready);
1133                mutex_lock(&match->notify_lock);
1134
1135                if (err != 0) {
1136                        /*
1137                         * Check to see if the notifcation got picked up and
1138                         * whether we should switch to wait killable.
1139                         */
1140                        if (!wait_killable && should_sleep_killable(match, &n))
1141                                continue;
1142
1143                        goto interrupted;
1144                }
1145
1146                addfd = list_first_entry_or_null(&n.addfd,
1147                                                 struct seccomp_kaddfd, list);
1148                /* Check if we were woken up by a addfd message */
1149                if (addfd)
1150                        seccomp_handle_addfd(addfd, &n);
1151
1152        }  while (n.state != SECCOMP_NOTIFY_REPLIED);
1153
1154        ret = n.val;
1155        err = n.error;
1156        flags = n.flags;
1157
1158interrupted:
1159        /* If there were any pending addfd calls, clear them out */
1160        list_for_each_entry_safe(addfd, tmp, &n.addfd, list) {
1161                /* The process went away before we got a chance to handle it */
1162                addfd->ret = -ESRCH;
1163                list_del_init(&addfd->list);
1164                complete(&addfd->completion);
1165        }
1166
1167        /*
1168         * Note that it's possible the listener died in between the time when
1169         * we were notified of a response (or a signal) and when we were able to
1170         * re-acquire the lock, so only delete from the list if the
1171         * notification actually exists.
1172         *
1173         * Also note that this test is only valid because there's no way to
1174         * *reattach* to a notifier right now. If one is added, we'll need to
1175         * keep track of the notif itself and make sure they match here.
1176         */
1177        if (match->notif)
1178                list_del(&n.list);
1179out:
1180        mutex_unlock(&match->notify_lock);
1181
1182        /* Userspace requests to continue the syscall. */
1183        if (flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE)
1184                return 0;
1185
1186        syscall_set_return_value(current, current_pt_regs(),
1187                                 err, ret);
1188        return -1;
1189}
1190
1191static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
1192                            const bool recheck_after_trace)
1193{
1194        u32 filter_ret, action;
1195        struct seccomp_filter *match = NULL;
1196        int data;
1197        struct seccomp_data sd_local;
1198
1199        /*
1200         * Make sure that any changes to mode from another thread have
1201         * been seen after SYSCALL_WORK_SECCOMP was seen.
1202         */
1203        smp_rmb();
1204
1205        if (!sd) {
1206                populate_seccomp_data(&sd_local);
1207                sd = &sd_local;
1208        }
1209
1210        filter_ret = seccomp_run_filters(sd, &match);
1211        data = filter_ret & SECCOMP_RET_DATA;
1212        action = filter_ret & SECCOMP_RET_ACTION_FULL;
1213
1214        switch (action) {
1215        case SECCOMP_RET_ERRNO:
1216                /* Set low-order bits as an errno, capped at MAX_ERRNO. */
1217                if (data > MAX_ERRNO)
1218                        data = MAX_ERRNO;
1219                syscall_set_return_value(current, current_pt_regs(),
1220                                         -data, 0);
1221                goto skip;
1222
1223        case SECCOMP_RET_TRAP:
1224                /* Show the handler the original registers. */
1225                syscall_rollback(current, current_pt_regs());
1226                /* Let the filter pass back 16 bits of data. */
1227                force_sig_seccomp(this_syscall, data, false);
1228                goto skip;
1229
1230        case SECCOMP_RET_TRACE:
1231                /* We've been put in this state by the ptracer already. */
1232                if (recheck_after_trace)
1233                        return 0;
1234
1235                /* ENOSYS these calls if there is no tracer attached. */
1236                if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
1237                        syscall_set_return_value(current,
1238                                                 current_pt_regs(),
1239                                                 -ENOSYS, 0);
1240                        goto skip;
1241                }
1242
1243                /* Allow the BPF to provide the event message */
1244                ptrace_event(PTRACE_EVENT_SECCOMP, data);
1245                /*
1246                 * The delivery of a fatal signal during event
1247                 * notification may silently skip tracer notification,
1248                 * which could leave us with a potentially unmodified
1249                 * syscall that the tracer would have liked to have
1250                 * changed. Since the process is about to die, we just
1251                 * force the syscall to be skipped and let the signal
1252                 * kill the process and correctly handle any tracer exit
1253                 * notifications.
1254                 */
1255                if (fatal_signal_pending(current))
1256                        goto skip;
1257                /* Check if the tracer forced the syscall to be skipped. */
1258                this_syscall = syscall_get_nr(current, current_pt_regs());
1259                if (this_syscall < 0)
1260                        goto skip;
1261
1262                /*
1263                 * Recheck the syscall, since it may have changed. This
1264                 * intentionally uses a NULL struct seccomp_data to force
1265                 * a reload of all registers. This does not goto skip since
1266                 * a skip would have already been reported.
1267                 */
1268                if (__seccomp_filter(this_syscall, NULL, true))
1269                        return -1;
1270
1271                return 0;
1272
1273        case SECCOMP_RET_USER_NOTIF:
1274                if (seccomp_do_user_notification(this_syscall, match, sd))
1275                        goto skip;
1276
1277                return 0;
1278
1279        case SECCOMP_RET_LOG:
1280                seccomp_log(this_syscall, 0, action, true);
1281                return 0;
1282
1283        case SECCOMP_RET_ALLOW:
1284                /*
1285                 * Note that the "match" filter will always be NULL for
1286                 * this action since SECCOMP_RET_ALLOW is the starting
1287                 * state in seccomp_run_filters().
1288                 */
1289                return 0;
1290
1291        case SECCOMP_RET_KILL_THREAD:
1292        case SECCOMP_RET_KILL_PROCESS:
1293        default:
1294                current->seccomp.mode = SECCOMP_MODE_DEAD;
1295                seccomp_log(this_syscall, SIGSYS, action, true);
1296                /* Dump core only if this is the last remaining thread. */
1297                if (action != SECCOMP_RET_KILL_THREAD ||
1298                    (atomic_read(&current->signal->live) == 1)) {
1299                        /* Show the original registers in the dump. */
1300                        syscall_rollback(current, current_pt_regs());
1301                        /* Trigger a coredump with SIGSYS */
1302                        force_sig_seccomp(this_syscall, data, true);
1303                } else {
1304                        do_exit(SIGSYS);
1305                }
1306                return -1; /* skip the syscall go directly to signal handling */
1307        }
1308
1309        unreachable();
1310
1311skip:
1312        seccomp_log(this_syscall, 0, action, match ? match->log : false);
1313        return -1;
1314}
1315#else
1316static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
1317                            const bool recheck_after_trace)
1318{
1319        BUG();
1320
1321        return -1;
1322}
1323#endif
1324
1325int __secure_computing(const struct seccomp_data *sd)
1326{
1327        int mode = current->seccomp.mode;
1328        int this_syscall;
1329
1330        if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
1331            unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
1332                return 0;
1333
1334        this_syscall = sd ? sd->nr :
1335                syscall_get_nr(current, current_pt_regs());
1336
1337        switch (mode) {
1338        case SECCOMP_MODE_STRICT:
1339                __secure_computing_strict(this_syscall);  /* may call do_exit */
1340                return 0;
1341        case SECCOMP_MODE_FILTER:
1342                return __seccomp_filter(this_syscall, sd, false);
1343        /* Surviving SECCOMP_RET_KILL_* must be proactively impossible. */
1344        case SECCOMP_MODE_DEAD:
1345                WARN_ON_ONCE(1);
1346                do_exit(SIGKILL);
1347                return -1;
1348        default:
1349                BUG();
1350        }
1351}
1352#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
1353
1354long prctl_get_seccomp(void)
1355{
1356        return current->seccomp.mode;
1357}
1358
1359/**
1360 * seccomp_set_mode_strict: internal function for setting strict seccomp
1361 *
1362 * Once current->seccomp.mode is non-zero, it may not be changed.
1363 *
1364 * Returns 0 on success or -EINVAL on failure.
1365 */
1366static long seccomp_set_mode_strict(void)
1367{
1368        const unsigned long seccomp_mode = SECCOMP_MODE_STRICT;
1369        long ret = -EINVAL;
1370
1371        spin_lock_irq(&current->sighand->siglock);
1372
1373        if (!seccomp_may_assign_mode(seccomp_mode))
1374                goto out;
1375
1376#ifdef TIF_NOTSC
1377        disable_TSC();
1378#endif
1379        seccomp_assign_mode(current, seccomp_mode, 0);
1380        ret = 0;
1381
1382out:
1383        spin_unlock_irq(&current->sighand->siglock);
1384
1385        return ret;
1386}
1387
1388#ifdef CONFIG_SECCOMP_FILTER
1389static void seccomp_notify_free(struct seccomp_filter *filter)
1390{
1391        kfree(filter->notif);
1392        filter->notif = NULL;
1393}
1394
1395static void seccomp_notify_detach(struct seccomp_filter *filter)
1396{
1397        struct seccomp_knotif *knotif;
1398
1399        if (!filter)
1400                return;
1401
1402        mutex_lock(&filter->notify_lock);
1403
1404        /*
1405         * If this file is being closed because e.g. the task who owned it
1406         * died, let's wake everyone up who was waiting on us.
1407         */
1408        list_for_each_entry(knotif, &filter->notif->notifications, list) {
1409                if (knotif->state == SECCOMP_NOTIFY_REPLIED)
1410                        continue;
1411
1412                knotif->state = SECCOMP_NOTIFY_REPLIED;
1413                knotif->error = -ENOSYS;
1414                knotif->val = 0;
1415
1416                /*
1417                 * We do not need to wake up any pending addfd messages, as
1418                 * the notifier will do that for us, as this just looks
1419                 * like a standard reply.
1420                 */
1421                complete(&knotif->ready);
1422        }
1423
1424        seccomp_notify_free(filter);
1425        mutex_unlock(&filter->notify_lock);
1426}
1427
1428static int seccomp_notify_release(struct inode *inode, struct file *file)
1429{
1430        struct seccomp_filter *filter = file->private_data;
1431
1432        seccomp_notify_detach(filter);
1433        __put_seccomp_filter(filter);
1434        return 0;
1435}
1436
1437/* must be called with notif_lock held */
1438static inline struct seccomp_knotif *
1439find_notification(struct seccomp_filter *filter, u64 id)
1440{
1441        struct seccomp_knotif *cur;
1442
1443        lockdep_assert_held(&filter->notify_lock);
1444
1445        list_for_each_entry(cur, &filter->notif->notifications, list) {
1446                if (cur->id == id)
1447                        return cur;
1448        }
1449
1450        return NULL;
1451}
1452
1453
1454static long seccomp_notify_recv(struct seccomp_filter *filter,
1455                                void __user *buf)
1456{
1457        struct seccomp_knotif *knotif = NULL, *cur;
1458        struct seccomp_notif unotif;
1459        ssize_t ret;
1460
1461        /* Verify that we're not given garbage to keep struct extensible. */
1462        ret = check_zeroed_user(buf, sizeof(unotif));
1463        if (ret < 0)
1464                return ret;
1465        if (!ret)
1466                return -EINVAL;
1467
1468        memset(&unotif, 0, sizeof(unotif));
1469
1470        ret = down_interruptible(&filter->notif->request);
1471        if (ret < 0)
1472                return ret;
1473
1474        mutex_lock(&filter->notify_lock);
1475        list_for_each_entry(cur, &filter->notif->notifications, list) {
1476                if (cur->state == SECCOMP_NOTIFY_INIT) {
1477                        knotif = cur;
1478                        break;
1479                }
1480        }
1481
1482        /*
1483         * If we didn't find a notification, it could be that the task was
1484         * interrupted by a fatal signal between the time we were woken and
1485         * when we were able to acquire the rw lock.
1486         */
1487        if (!knotif) {
1488                ret = -ENOENT;
1489                goto out;
1490        }
1491
1492        unotif.id = knotif->id;
1493        unotif.pid = task_pid_vnr(knotif->task);
1494        unotif.data = *(knotif->data);
1495
1496        knotif->state = SECCOMP_NOTIFY_SENT;
1497        wake_up_poll(&filter->wqh, EPOLLOUT | EPOLLWRNORM);
1498        ret = 0;
1499out:
1500        mutex_unlock(&filter->notify_lock);
1501
1502        if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) {
1503                ret = -EFAULT;
1504
1505                /*
1506                 * Userspace screwed up. To make sure that we keep this
1507                 * notification alive, let's reset it back to INIT. It
1508                 * may have died when we released the lock, so we need to make
1509                 * sure it's still around.
1510                 */
1511                mutex_lock(&filter->notify_lock);
1512                knotif = find_notification(filter, unotif.id);
1513                if (knotif) {
1514                        /* Reset the process to make sure it's not stuck */
1515                        if (should_sleep_killable(filter, knotif))
1516                                complete(&knotif->ready);
1517                        knotif->state = SECCOMP_NOTIFY_INIT;
1518                        up(&filter->notif->request);
1519                }
1520                mutex_unlock(&filter->notify_lock);
1521        }
1522
1523        return ret;
1524}
1525
1526static long seccomp_notify_send(struct seccomp_filter *filter,
1527                                void __user *buf)
1528{
1529        struct seccomp_notif_resp resp = {};
1530        struct seccomp_knotif *knotif;
1531        long ret;
1532
1533        if (copy_from_user(&resp, buf, sizeof(resp)))
1534                return -EFAULT;
1535
1536        if (resp.flags & ~SECCOMP_USER_NOTIF_FLAG_CONTINUE)
1537                return -EINVAL;
1538
1539        if ((resp.flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) &&
1540            (resp.error || resp.val))
1541                return -EINVAL;
1542
1543        ret = mutex_lock_interruptible(&filter->notify_lock);
1544        if (ret < 0)
1545                return ret;
1546
1547        knotif = find_notification(filter, resp.id);
1548        if (!knotif) {
1549                ret = -ENOENT;
1550                goto out;
1551        }
1552
1553        /* Allow exactly one reply. */
1554        if (knotif->state != SECCOMP_NOTIFY_SENT) {
1555                ret = -EINPROGRESS;
1556                goto out;
1557        }
1558
1559        ret = 0;
1560        knotif->state = SECCOMP_NOTIFY_REPLIED;
1561        knotif->error = resp.error;
1562        knotif->val = resp.val;
1563        knotif->flags = resp.flags;
1564        complete(&knotif->ready);
1565out:
1566        mutex_unlock(&filter->notify_lock);
1567        return ret;
1568}
1569
1570static long seccomp_notify_id_valid(struct seccomp_filter *filter,
1571                                    void __user *buf)
1572{
1573        struct seccomp_knotif *knotif;
1574        u64 id;
1575        long ret;
1576
1577        if (copy_from_user(&id, buf, sizeof(id)))
1578                return -EFAULT;
1579
1580        ret = mutex_lock_interruptible(&filter->notify_lock);
1581        if (ret < 0)
1582                return ret;
1583
1584        knotif = find_notification(filter, id);
1585        if (knotif && knotif->state == SECCOMP_NOTIFY_SENT)
1586                ret = 0;
1587        else
1588                ret = -ENOENT;
1589
1590        mutex_unlock(&filter->notify_lock);
1591        return ret;
1592}
1593
1594static long seccomp_notify_addfd(struct seccomp_filter *filter,
1595                                 struct seccomp_notif_addfd __user *uaddfd,
1596                                 unsigned int size)
1597{
1598        struct seccomp_notif_addfd addfd;
1599        struct seccomp_knotif *knotif;
1600        struct seccomp_kaddfd kaddfd;
1601        int ret;
1602
1603        BUILD_BUG_ON(sizeof(addfd) < SECCOMP_NOTIFY_ADDFD_SIZE_VER0);
1604        BUILD_BUG_ON(sizeof(addfd) != SECCOMP_NOTIFY_ADDFD_SIZE_LATEST);
1605
1606        if (size < SECCOMP_NOTIFY_ADDFD_SIZE_VER0 || size >= PAGE_SIZE)
1607                return -EINVAL;
1608
1609        ret = copy_struct_from_user(&addfd, sizeof(addfd), uaddfd, size);
1610        if (ret)
1611                return ret;
1612
1613        if (addfd.newfd_flags & ~O_CLOEXEC)
1614                return -EINVAL;
1615
1616        if (addfd.flags & ~(SECCOMP_ADDFD_FLAG_SETFD | SECCOMP_ADDFD_FLAG_SEND))
1617                return -EINVAL;
1618
1619        if (addfd.newfd && !(addfd.flags & SECCOMP_ADDFD_FLAG_SETFD))
1620                return -EINVAL;
1621
1622        kaddfd.file = fget(addfd.srcfd);
1623        if (!kaddfd.file)
1624                return -EBADF;
1625
1626        kaddfd.ioctl_flags = addfd.flags;
1627        kaddfd.flags = addfd.newfd_flags;
1628        kaddfd.setfd = addfd.flags & SECCOMP_ADDFD_FLAG_SETFD;
1629        kaddfd.fd = addfd.newfd;
1630        init_completion(&kaddfd.completion);
1631
1632        ret = mutex_lock_interruptible(&filter->notify_lock);
1633        if (ret < 0)
1634                goto out;
1635
1636        knotif = find_notification(filter, addfd.id);
1637        if (!knotif) {
1638                ret = -ENOENT;
1639                goto out_unlock;
1640        }
1641
1642        /*
1643         * We do not want to allow for FD injection to occur before the
1644         * notification has been picked up by a userspace handler, or after
1645         * the notification has been replied to.
1646         */
1647        if (knotif->state != SECCOMP_NOTIFY_SENT) {
1648                ret = -EINPROGRESS;
1649                goto out_unlock;
1650        }
1651
1652        if (addfd.flags & SECCOMP_ADDFD_FLAG_SEND) {
1653                /*
1654                 * Disallow queuing an atomic addfd + send reply while there are
1655                 * some addfd requests still to process.
1656                 *
1657                 * There is no clear reason to support it and allows us to keep
1658                 * the loop on the other side straight-forward.
1659                 */
1660                if (!list_empty(&knotif->addfd)) {
1661                        ret = -EBUSY;
1662                        goto out_unlock;
1663                }
1664
1665                /* Allow exactly only one reply */
1666                knotif->state = SECCOMP_NOTIFY_REPLIED;
1667        }
1668
1669        list_add(&kaddfd.list, &knotif->addfd);
1670        complete(&knotif->ready);
1671        mutex_unlock(&filter->notify_lock);
1672
1673        /* Now we wait for it to be processed or be interrupted */
1674        ret = wait_for_completion_interruptible(&kaddfd.completion);
1675        if (ret == 0) {
1676                /*
1677                 * We had a successful completion. The other side has already
1678                 * removed us from the addfd queue, and
1679                 * wait_for_completion_interruptible has a memory barrier upon
1680                 * success that lets us read this value directly without
1681                 * locking.
1682                 */
1683                ret = kaddfd.ret;
1684                goto out;
1685        }
1686
1687        mutex_lock(&filter->notify_lock);
1688        /*
1689         * Even though we were woken up by a signal and not a successful
1690         * completion, a completion may have happened in the mean time.
1691         *
1692         * We need to check again if the addfd request has been handled,
1693         * and if not, we will remove it from the queue.
1694         */
1695        if (list_empty(&kaddfd.list))
1696                ret = kaddfd.ret;
1697        else
1698                list_del(&kaddfd.list);
1699
1700out_unlock:
1701        mutex_unlock(&filter->notify_lock);
1702out:
1703        fput(kaddfd.file);
1704
1705        return ret;
1706}
1707
1708static long seccomp_notify_ioctl(struct file *file, unsigned int cmd,
1709                                 unsigned long arg)
1710{
1711        struct seccomp_filter *filter = file->private_data;
1712        void __user *buf = (void __user *)arg;
1713
1714        /* Fixed-size ioctls */
1715        switch (cmd) {
1716        case SECCOMP_IOCTL_NOTIF_RECV:
1717                return seccomp_notify_recv(filter, buf);
1718        case SECCOMP_IOCTL_NOTIF_SEND:
1719                return seccomp_notify_send(filter, buf);
1720        case SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR:
1721        case SECCOMP_IOCTL_NOTIF_ID_VALID:
1722                return seccomp_notify_id_valid(filter, buf);
1723        }
1724
1725        /* Extensible Argument ioctls */
1726#define EA_IOCTL(cmd)   ((cmd) & ~(IOC_INOUT | IOCSIZE_MASK))
1727        switch (EA_IOCTL(cmd)) {
1728        case EA_IOCTL(SECCOMP_IOCTL_NOTIF_ADDFD):
1729                return seccomp_notify_addfd(filter, buf, _IOC_SIZE(cmd));
1730        default:
1731                return -EINVAL;
1732        }
1733}
1734
1735static __poll_t seccomp_notify_poll(struct file *file,
1736                                    struct poll_table_struct *poll_tab)
1737{
1738        struct seccomp_filter *filter = file->private_data;
1739        __poll_t ret = 0;
1740        struct seccomp_knotif *cur;
1741
1742        poll_wait(file, &filter->wqh, poll_tab);
1743
1744        if (mutex_lock_interruptible(&filter->notify_lock) < 0)
1745                return EPOLLERR;
1746
1747        list_for_each_entry(cur, &filter->notif->notifications, list) {
1748                if (cur->state == SECCOMP_NOTIFY_INIT)
1749                        ret |= EPOLLIN | EPOLLRDNORM;
1750                if (cur->state == SECCOMP_NOTIFY_SENT)
1751                        ret |= EPOLLOUT | EPOLLWRNORM;
1752                if ((ret & EPOLLIN) && (ret & EPOLLOUT))
1753                        break;
1754        }
1755
1756        mutex_unlock(&filter->notify_lock);
1757
1758        if (refcount_read(&filter->users) == 0)
1759                ret |= EPOLLHUP;
1760
1761        return ret;
1762}
1763
1764static const struct file_operations seccomp_notify_ops = {
1765        .poll = seccomp_notify_poll,
1766        .release = seccomp_notify_release,
1767        .unlocked_ioctl = seccomp_notify_ioctl,
1768        .compat_ioctl = seccomp_notify_ioctl,
1769};
1770
1771static struct file *init_listener(struct seccomp_filter *filter)
1772{
1773        struct file *ret;
1774
1775        ret = ERR_PTR(-ENOMEM);
1776        filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL);
1777        if (!filter->notif)
1778                goto out;
1779
1780        sema_init(&filter->notif->request, 0);
1781        filter->notif->next_id = get_random_u64();
1782        INIT_LIST_HEAD(&filter->notif->notifications);
1783
1784        ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops,
1785                                 filter, O_RDWR);
1786        if (IS_ERR(ret))
1787                goto out_notif;
1788
1789        /* The file has a reference to it now */
1790        __get_seccomp_filter(filter);
1791
1792out_notif:
1793        if (IS_ERR(ret))
1794                seccomp_notify_free(filter);
1795out:
1796        return ret;
1797}
1798
1799/*
1800 * Does @new_child have a listener while an ancestor also has a listener?
1801 * If so, we'll want to reject this filter.
1802 * This only has to be tested for the current process, even in the TSYNC case,
1803 * because TSYNC installs @child with the same parent on all threads.
1804 * Note that @new_child is not hooked up to its parent at this point yet, so
1805 * we use current->seccomp.filter.
1806 */
1807static bool has_duplicate_listener(struct seccomp_filter *new_child)
1808{
1809        struct seccomp_filter *cur;
1810
1811        /* must be protected against concurrent TSYNC */
1812        lockdep_assert_held(&current->sighand->siglock);
1813
1814        if (!new_child->notif)
1815                return false;
1816        for (cur = current->seccomp.filter; cur; cur = cur->prev) {
1817                if (cur->notif)
1818                        return true;
1819        }
1820
1821        return false;
1822}
1823
1824/**
1825 * seccomp_set_mode_filter: internal function for setting seccomp filter
1826 * @flags:  flags to change filter behavior
1827 * @filter: struct sock_fprog containing filter
1828 *
1829 * This function may be called repeatedly to install additional filters.
1830 * Every filter successfully installed will be evaluated (in reverse order)
1831 * for each system call the task makes.
1832 *
1833 * Once current->seccomp.mode is non-zero, it may not be changed.
1834 *
1835 * Returns 0 on success or -EINVAL on failure.
1836 */
1837static long seccomp_set_mode_filter(unsigned int flags,
1838                                    const char __user *filter)
1839{
1840        const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
1841        struct seccomp_filter *prepared = NULL;
1842        long ret = -EINVAL;
1843        int listener = -1;
1844        struct file *listener_f = NULL;
1845
1846        /* Validate flags. */
1847        if (flags & ~SECCOMP_FILTER_FLAG_MASK)
1848                return -EINVAL;
1849
1850        /*
1851         * In the successful case, NEW_LISTENER returns the new listener fd.
1852         * But in the failure case, TSYNC returns the thread that died. If you
1853         * combine these two flags, there's no way to tell whether something
1854         * succeeded or failed. So, let's disallow this combination if the user
1855         * has not explicitly requested no errors from TSYNC.
1856         */
1857        if ((flags & SECCOMP_FILTER_FLAG_TSYNC) &&
1858            (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) &&
1859            ((flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH) == 0))
1860                return -EINVAL;
1861
1862        /*
1863         * The SECCOMP_FILTER_FLAG_WAIT_KILLABLE_SENT flag doesn't make sense
1864         * without the SECCOMP_FILTER_FLAG_NEW_LISTENER flag.
1865         */
1866        if ((flags & SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV) &&
1867            ((flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) == 0))
1868                return -EINVAL;
1869
1870        /* Prepare the new filter before holding any locks. */
1871        prepared = seccomp_prepare_user_filter(filter);
1872        if (IS_ERR(prepared))
1873                return PTR_ERR(prepared);
1874
1875        if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
1876                listener = get_unused_fd_flags(O_CLOEXEC);
1877                if (listener < 0) {
1878                        ret = listener;
1879                        goto out_free;
1880                }
1881
1882                listener_f = init_listener(prepared);
1883                if (IS_ERR(listener_f)) {
1884                        put_unused_fd(listener);
1885                        ret = PTR_ERR(listener_f);
1886                        goto out_free;
1887                }
1888        }
1889
1890        /*
1891         * Make sure we cannot change seccomp or nnp state via TSYNC
1892         * while another thread is in the middle of calling exec.
1893         */
1894        if (flags & SECCOMP_FILTER_FLAG_TSYNC &&
1895            mutex_lock_killable(&current->signal->cred_guard_mutex))
1896                goto out_put_fd;
1897
1898        spin_lock_irq(&current->sighand->siglock);
1899
1900        if (!seccomp_may_assign_mode(seccomp_mode))
1901                goto out;
1902
1903        if (has_duplicate_listener(prepared)) {
1904                ret = -EBUSY;
1905                goto out;
1906        }
1907
1908        ret = seccomp_attach_filter(flags, prepared);
1909        if (ret)
1910                goto out;
1911        /* Do not free the successfully attached filter. */
1912        prepared = NULL;
1913
1914        seccomp_assign_mode(current, seccomp_mode, flags);
1915out:
1916        spin_unlock_irq(&current->sighand->siglock);
1917        if (flags & SECCOMP_FILTER_FLAG_TSYNC)
1918                mutex_unlock(&current->signal->cred_guard_mutex);
1919out_put_fd:
1920        if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
1921                if (ret) {
1922                        listener_f->private_data = NULL;
1923                        fput(listener_f);
1924                        put_unused_fd(listener);
1925                        seccomp_notify_detach(prepared);
1926                } else {
1927                        fd_install(listener, listener_f);
1928                        ret = listener;
1929                }
1930        }
1931out_free:
1932        seccomp_filter_free(prepared);
1933        return ret;
1934}
1935#else
1936static inline long seccomp_set_mode_filter(unsigned int flags,
1937                                           const char __user *filter)
1938{
1939        return -EINVAL;
1940}
1941#endif
1942
1943static long seccomp_get_action_avail(const char __user *uaction)
1944{
1945        u32 action;
1946
1947        if (copy_from_user(&action, uaction, sizeof(action)))
1948                return -EFAULT;
1949
1950        switch (action) {
1951        case SECCOMP_RET_KILL_PROCESS:
1952        case SECCOMP_RET_KILL_THREAD:
1953        case SECCOMP_RET_TRAP:
1954        case SECCOMP_RET_ERRNO:
1955        case SECCOMP_RET_USER_NOTIF:
1956        case SECCOMP_RET_TRACE:
1957        case SECCOMP_RET_LOG:
1958        case SECCOMP_RET_ALLOW:
1959                break;
1960        default:
1961                return -EOPNOTSUPP;
1962        }
1963
1964        return 0;
1965}
1966
1967static long seccomp_get_notif_sizes(void __user *usizes)
1968{
1969        struct seccomp_notif_sizes sizes = {
1970                .seccomp_notif = sizeof(struct seccomp_notif),
1971                .seccomp_notif_resp = sizeof(struct seccomp_notif_resp),
1972                .seccomp_data = sizeof(struct seccomp_data),
1973        };
1974
1975        if (copy_to_user(usizes, &sizes, sizeof(sizes)))
1976                return -EFAULT;
1977
1978        return 0;
1979}
1980
1981/* Common entry point for both prctl and syscall. */
1982static long do_seccomp(unsigned int op, unsigned int flags,
1983                       void __user *uargs)
1984{
1985        switch (op) {
1986        case SECCOMP_SET_MODE_STRICT:
1987                if (flags != 0 || uargs != NULL)
1988                        return -EINVAL;
1989                return seccomp_set_mode_strict();
1990        case SECCOMP_SET_MODE_FILTER:
1991                return seccomp_set_mode_filter(flags, uargs);
1992        case SECCOMP_GET_ACTION_AVAIL:
1993                if (flags != 0)
1994                        return -EINVAL;
1995
1996                return seccomp_get_action_avail(uargs);
1997        case SECCOMP_GET_NOTIF_SIZES:
1998                if (flags != 0)
1999                        return -EINVAL;
2000
2001                return seccomp_get_notif_sizes(uargs);
2002        default:
2003                return -EINVAL;
2004        }
2005}
2006
2007SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
2008                         void __user *, uargs)
2009{
2010        return do_seccomp(op, flags, uargs);
2011}
2012
2013/**
2014 * prctl_set_seccomp: configures current->seccomp.mode
2015 * @seccomp_mode: requested mode to use
2016 * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
2017 *
2018 * Returns 0 on success or -EINVAL on failure.
2019 */
2020long prctl_set_seccomp(unsigned long seccomp_mode, void __user *filter)
2021{
2022        unsigned int op;
2023        void __user *uargs;
2024
2025        switch (seccomp_mode) {
2026        case SECCOMP_MODE_STRICT:
2027                op = SECCOMP_SET_MODE_STRICT;
2028                /*
2029                 * Setting strict mode through prctl always ignored filter,
2030                 * so make sure it is always NULL here to pass the internal
2031                 * check in do_seccomp().
2032                 */
2033                uargs = NULL;
2034                break;
2035        case SECCOMP_MODE_FILTER:
2036                op = SECCOMP_SET_MODE_FILTER;
2037                uargs = filter;
2038                break;
2039        default:
2040                return -EINVAL;
2041        }
2042
2043        /* prctl interface doesn't have flags, so they are always zero. */
2044        return do_seccomp(op, 0, uargs);
2045}
2046
2047#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
2048static struct seccomp_filter *get_nth_filter(struct task_struct *task,
2049                                             unsigned long filter_off)
2050{
2051        struct seccomp_filter *orig, *filter;
2052        unsigned long count;
2053
2054        /*
2055         * Note: this is only correct because the caller should be the (ptrace)
2056         * tracer of the task, otherwise lock_task_sighand is needed.
2057         */
2058        spin_lock_irq(&task->sighand->siglock);
2059
2060        if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
2061                spin_unlock_irq(&task->sighand->siglock);
2062                return ERR_PTR(-EINVAL);
2063        }
2064
2065        orig = task->seccomp.filter;
2066        __get_seccomp_filter(orig);
2067        spin_unlock_irq(&task->sighand->siglock);
2068
2069        count = 0;
2070        for (filter = orig; filter; filter = filter->prev)
2071                count++;
2072
2073        if (filter_off >= count) {
2074                filter = ERR_PTR(-ENOENT);
2075                goto out;
2076        }
2077
2078        count -= filter_off;
2079        for (filter = orig; filter && count > 1; filter = filter->prev)
2080                count--;
2081
2082        if (WARN_ON(count != 1 || !filter)) {
2083                filter = ERR_PTR(-ENOENT);
2084                goto out;
2085        }
2086
2087        __get_seccomp_filter(filter);
2088
2089out:
2090        __put_seccomp_filter(orig);
2091        return filter;
2092}
2093
2094long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
2095                        void __user *data)
2096{
2097        struct seccomp_filter *filter;
2098        struct sock_fprog_kern *fprog;
2099        long ret;
2100
2101        if (!capable(CAP_SYS_ADMIN) ||
2102            current->seccomp.mode != SECCOMP_MODE_DISABLED) {
2103                return -EACCES;
2104        }
2105
2106        filter = get_nth_filter(task, filter_off);
2107        if (IS_ERR(filter))
2108                return PTR_ERR(filter);
2109
2110        fprog = filter->prog->orig_prog;
2111        if (!fprog) {
2112                /* This must be a new non-cBPF filter, since we save
2113                 * every cBPF filter's orig_prog above when
2114                 * CONFIG_CHECKPOINT_RESTORE is enabled.
2115                 */
2116                ret = -EMEDIUMTYPE;
2117                goto out;
2118        }
2119
2120        ret = fprog->len;
2121        if (!data)
2122                goto out;
2123
2124        if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
2125                ret = -EFAULT;
2126
2127out:
2128        __put_seccomp_filter(filter);
2129        return ret;
2130}
2131
2132long seccomp_get_metadata(struct task_struct *task,
2133                          unsigned long size, void __user *data)
2134{
2135        long ret;
2136        struct seccomp_filter *filter;
2137        struct seccomp_metadata kmd = {};
2138
2139        if (!capable(CAP_SYS_ADMIN) ||
2140            current->seccomp.mode != SECCOMP_MODE_DISABLED) {
2141                return -EACCES;
2142        }
2143
2144        size = min_t(unsigned long, size, sizeof(kmd));
2145
2146        if (size < sizeof(kmd.filter_off))
2147                return -EINVAL;
2148
2149        if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off)))
2150                return -EFAULT;
2151
2152        filter = get_nth_filter(task, kmd.filter_off);
2153        if (IS_ERR(filter))
2154                return PTR_ERR(filter);
2155
2156        if (filter->log)
2157                kmd.flags |= SECCOMP_FILTER_FLAG_LOG;
2158
2159        ret = size;
2160        if (copy_to_user(data, &kmd, size))
2161                ret = -EFAULT;
2162
2163        __put_seccomp_filter(filter);
2164        return ret;
2165}
2166#endif
2167
2168#ifdef CONFIG_SYSCTL
2169
2170/* Human readable action names for friendly sysctl interaction */
2171#define SECCOMP_RET_KILL_PROCESS_NAME   "kill_process"
2172#define SECCOMP_RET_KILL_THREAD_NAME    "kill_thread"
2173#define SECCOMP_RET_TRAP_NAME           "trap"
2174#define SECCOMP_RET_ERRNO_NAME          "errno"
2175#define SECCOMP_RET_USER_NOTIF_NAME     "user_notif"
2176#define SECCOMP_RET_TRACE_NAME          "trace"
2177#define SECCOMP_RET_LOG_NAME            "log"
2178#define SECCOMP_RET_ALLOW_NAME          "allow"
2179
2180static const char seccomp_actions_avail[] =
2181                                SECCOMP_RET_KILL_PROCESS_NAME   " "
2182                                SECCOMP_RET_KILL_THREAD_NAME    " "
2183                                SECCOMP_RET_TRAP_NAME           " "
2184                                SECCOMP_RET_ERRNO_NAME          " "
2185                                SECCOMP_RET_USER_NOTIF_NAME     " "
2186                                SECCOMP_RET_TRACE_NAME          " "
2187                                SECCOMP_RET_LOG_NAME            " "
2188                                SECCOMP_RET_ALLOW_NAME;
2189
2190struct seccomp_log_name {
2191        u32             log;
2192        const char      *name;
2193};
2194
2195static const struct seccomp_log_name seccomp_log_names[] = {
2196        { SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME },
2197        { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME },
2198        { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME },
2199        { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME },
2200        { SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME },
2201        { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME },
2202        { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME },
2203        { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME },
2204        { }
2205};
2206
2207static bool seccomp_names_from_actions_logged(char *names, size_t size,
2208                                              u32 actions_logged,
2209                                              const char *sep)
2210{
2211        const struct seccomp_log_name *cur;
2212        bool append_sep = false;
2213
2214        for (cur = seccomp_log_names; cur->name && size; cur++) {
2215                ssize_t ret;
2216
2217                if (!(actions_logged & cur->log))
2218                        continue;
2219
2220                if (append_sep) {
2221                        ret = strscpy(names, sep, size);
2222                        if (ret < 0)
2223                                return false;
2224
2225                        names += ret;
2226                        size -= ret;
2227                } else
2228                        append_sep = true;
2229
2230                ret = strscpy(names, cur->name, size);
2231                if (ret < 0)
2232                        return false;
2233
2234                names += ret;
2235                size -= ret;
2236        }
2237
2238        return true;
2239}
2240
2241static bool seccomp_action_logged_from_name(u32 *action_logged,
2242                                            const char *name)
2243{
2244        const struct seccomp_log_name *cur;
2245
2246        for (cur = seccomp_log_names; cur->name; cur++) {
2247                if (!strcmp(cur->name, name)) {
2248                        *action_logged = cur->log;
2249                        return true;
2250                }
2251        }
2252
2253        return false;
2254}
2255
2256static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names)
2257{
2258        char *name;
2259
2260        *actions_logged = 0;
2261        while ((name = strsep(&names, " ")) && *name) {
2262                u32 action_logged = 0;
2263
2264                if (!seccomp_action_logged_from_name(&action_logged, name))
2265                        return false;
2266
2267                *actions_logged |= action_logged;
2268        }
2269
2270        return true;
2271}
2272
2273static int read_actions_logged(struct ctl_table *ro_table, void *buffer,
2274                               size_t *lenp, loff_t *ppos)
2275{
2276        char names[sizeof(seccomp_actions_avail)];
2277        struct ctl_table table;
2278
2279        memset(names, 0, sizeof(names));
2280
2281        if (!seccomp_names_from_actions_logged(names, sizeof(names),
2282                                               seccomp_actions_logged, " "))
2283                return -EINVAL;
2284
2285        table = *ro_table;
2286        table.data = names;
2287        table.maxlen = sizeof(names);
2288        return proc_dostring(&table, 0, buffer, lenp, ppos);
2289}
2290
2291static int write_actions_logged(struct ctl_table *ro_table, void *buffer,
2292                                size_t *lenp, loff_t *ppos, u32 *actions_logged)
2293{
2294        char names[sizeof(seccomp_actions_avail)];
2295        struct ctl_table table;
2296        int ret;
2297
2298        if (!capable(CAP_SYS_ADMIN))
2299                return -EPERM;
2300
2301        memset(names, 0, sizeof(names));
2302
2303        table = *ro_table;
2304        table.data = names;
2305        table.maxlen = sizeof(names);
2306        ret = proc_dostring(&table, 1, buffer, lenp, ppos);
2307        if (ret)
2308                return ret;
2309
2310        if (!seccomp_actions_logged_from_names(actions_logged, table.data))
2311                return -EINVAL;
2312
2313        if (*actions_logged & SECCOMP_LOG_ALLOW)
2314                return -EINVAL;
2315
2316        seccomp_actions_logged = *actions_logged;
2317        return 0;
2318}
2319
2320static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged,
2321                                 int ret)
2322{
2323        char names[sizeof(seccomp_actions_avail)];
2324        char old_names[sizeof(seccomp_actions_avail)];
2325        const char *new = names;
2326        const char *old = old_names;
2327
2328        if (!audit_enabled)
2329                return;
2330
2331        memset(names, 0, sizeof(names));
2332        memset(old_names, 0, sizeof(old_names));
2333
2334        if (ret)
2335                new = "?";
2336        else if (!actions_logged)
2337                new = "(none)";
2338        else if (!seccomp_names_from_actions_logged(names, sizeof(names),
2339                                                    actions_logged, ","))
2340                new = "?";
2341
2342        if (!old_actions_logged)
2343                old = "(none)";
2344        else if (!seccomp_names_from_actions_logged(old_names,
2345                                                    sizeof(old_names),
2346                                                    old_actions_logged, ","))
2347                old = "?";
2348
2349        return audit_seccomp_actions_logged(new, old, !ret);
2350}
2351
2352static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write,
2353                                          void *buffer, size_t *lenp,
2354                                          loff_t *ppos)
2355{
2356        int ret;
2357
2358        if (write) {
2359                u32 actions_logged = 0;
2360                u32 old_actions_logged = seccomp_actions_logged;
2361
2362                ret = write_actions_logged(ro_table, buffer, lenp, ppos,
2363                                           &actions_logged);
2364                audit_actions_logged(actions_logged, old_actions_logged, ret);
2365        } else
2366                ret = read_actions_logged(ro_table, buffer, lenp, ppos);
2367
2368        return ret;
2369}
2370
2371static struct ctl_path seccomp_sysctl_path[] = {
2372        { .procname = "kernel", },
2373        { .procname = "seccomp", },
2374        { }
2375};
2376
2377static struct ctl_table seccomp_sysctl_table[] = {
2378        {
2379                .procname       = "actions_avail",
2380                .data           = (void *) &seccomp_actions_avail,
2381                .maxlen         = sizeof(seccomp_actions_avail),
2382                .mode           = 0444,
2383                .proc_handler   = proc_dostring,
2384        },
2385        {
2386                .procname       = "actions_logged",
2387                .mode           = 0644,
2388                .proc_handler   = seccomp_actions_logged_handler,
2389        },
2390        { }
2391};
2392
2393static int __init seccomp_sysctl_init(void)
2394{
2395        struct ctl_table_header *hdr;
2396
2397        hdr = register_sysctl_paths(seccomp_sysctl_path, seccomp_sysctl_table);
2398        if (!hdr)
2399                pr_warn("sysctl registration failed\n");
2400        else
2401                kmemleak_not_leak(hdr);
2402
2403        return 0;
2404}
2405
2406device_initcall(seccomp_sysctl_init)
2407
2408#endif /* CONFIG_SYSCTL */
2409
2410#ifdef CONFIG_SECCOMP_CACHE_DEBUG
2411/* Currently CONFIG_SECCOMP_CACHE_DEBUG implies SECCOMP_ARCH_NATIVE */
2412static void proc_pid_seccomp_cache_arch(struct seq_file *m, const char *name,
2413                                        const void *bitmap, size_t bitmap_size)
2414{
2415        int nr;
2416
2417        for (nr = 0; nr < bitmap_size; nr++) {
2418                bool cached = test_bit(nr, bitmap);
2419                char *status = cached ? "ALLOW" : "FILTER";
2420
2421                seq_printf(m, "%s %d %s\n", name, nr, status);
2422        }
2423}
2424
2425int proc_pid_seccomp_cache(struct seq_file *m, struct pid_namespace *ns,
2426                           struct pid *pid, struct task_struct *task)
2427{
2428        struct seccomp_filter *f;
2429        unsigned long flags;
2430
2431        /*
2432         * We don't want some sandboxed process to know what their seccomp
2433         * filters consist of.
2434         */
2435        if (!file_ns_capable(m->file, &init_user_ns, CAP_SYS_ADMIN))
2436                return -EACCES;
2437
2438        if (!lock_task_sighand(task, &flags))
2439                return -ESRCH;
2440
2441        f = READ_ONCE(task->seccomp.filter);
2442        if (!f) {
2443                unlock_task_sighand(task, &flags);
2444                return 0;
2445        }
2446
2447        /* prevent filter from being freed while we are printing it */
2448        __get_seccomp_filter(f);
2449        unlock_task_sighand(task, &flags);
2450
2451        proc_pid_seccomp_cache_arch(m, SECCOMP_ARCH_NATIVE_NAME,
2452                                    f->cache.allow_native,
2453                                    SECCOMP_ARCH_NATIVE_NR);
2454
2455#ifdef SECCOMP_ARCH_COMPAT
2456        proc_pid_seccomp_cache_arch(m, SECCOMP_ARCH_COMPAT_NAME,
2457                                    f->cache.allow_compat,
2458                                    SECCOMP_ARCH_COMPAT_NR);
2459#endif /* SECCOMP_ARCH_COMPAT */
2460
2461        __put_seccomp_filter(f);
2462        return 0;
2463}
2464#endif /* CONFIG_SECCOMP_CACHE_DEBUG */
2465