linux/fs/coredump.c
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   1// SPDX-License-Identifier: GPL-2.0
   2#include <linux/slab.h>
   3#include <linux/file.h>
   4#include <linux/fdtable.h>
   5#include <linux/freezer.h>
   6#include <linux/mm.h>
   7#include <linux/stat.h>
   8#include <linux/fcntl.h>
   9#include <linux/swap.h>
  10#include <linux/ctype.h>
  11#include <linux/string.h>
  12#include <linux/init.h>
  13#include <linux/pagemap.h>
  14#include <linux/perf_event.h>
  15#include <linux/highmem.h>
  16#include <linux/spinlock.h>
  17#include <linux/key.h>
  18#include <linux/personality.h>
  19#include <linux/binfmts.h>
  20#include <linux/coredump.h>
  21#include <linux/sched/coredump.h>
  22#include <linux/sched/signal.h>
  23#include <linux/sched/task_stack.h>
  24#include <linux/utsname.h>
  25#include <linux/pid_namespace.h>
  26#include <linux/module.h>
  27#include <linux/namei.h>
  28#include <linux/mount.h>
  29#include <linux/security.h>
  30#include <linux/syscalls.h>
  31#include <linux/tsacct_kern.h>
  32#include <linux/cn_proc.h>
  33#include <linux/audit.h>
  34#include <linux/tracehook.h>
  35#include <linux/kmod.h>
  36#include <linux/fsnotify.h>
  37#include <linux/fs_struct.h>
  38#include <linux/pipe_fs_i.h>
  39#include <linux/oom.h>
  40#include <linux/compat.h>
  41#include <linux/fs.h>
  42#include <linux/path.h>
  43#include <linux/timekeeping.h>
  44
  45#include <linux/uaccess.h>
  46#include <asm/mmu_context.h>
  47#include <asm/tlb.h>
  48#include <asm/exec.h>
  49
  50#include <trace/events/task.h>
  51#include "internal.h"
  52
  53#include <trace/events/sched.h>
  54
  55int core_uses_pid;
  56unsigned int core_pipe_limit;
  57char core_pattern[CORENAME_MAX_SIZE] = "core";
  58static int core_name_size = CORENAME_MAX_SIZE;
  59
  60struct core_name {
  61        char *corename;
  62        int used, size;
  63};
  64
  65/* The maximal length of core_pattern is also specified in sysctl.c */
  66
  67static int expand_corename(struct core_name *cn, int size)
  68{
  69        char *corename = krealloc(cn->corename, size, GFP_KERNEL);
  70
  71        if (!corename)
  72                return -ENOMEM;
  73
  74        if (size > core_name_size) /* racy but harmless */
  75                core_name_size = size;
  76
  77        cn->size = ksize(corename);
  78        cn->corename = corename;
  79        return 0;
  80}
  81
  82static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
  83                                     va_list arg)
  84{
  85        int free, need;
  86        va_list arg_copy;
  87
  88again:
  89        free = cn->size - cn->used;
  90
  91        va_copy(arg_copy, arg);
  92        need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
  93        va_end(arg_copy);
  94
  95        if (need < free) {
  96                cn->used += need;
  97                return 0;
  98        }
  99
 100        if (!expand_corename(cn, cn->size + need - free + 1))
 101                goto again;
 102
 103        return -ENOMEM;
 104}
 105
 106static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
 107{
 108        va_list arg;
 109        int ret;
 110
 111        va_start(arg, fmt);
 112        ret = cn_vprintf(cn, fmt, arg);
 113        va_end(arg);
 114
 115        return ret;
 116}
 117
 118static __printf(2, 3)
 119int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
 120{
 121        int cur = cn->used;
 122        va_list arg;
 123        int ret;
 124
 125        va_start(arg, fmt);
 126        ret = cn_vprintf(cn, fmt, arg);
 127        va_end(arg);
 128
 129        if (ret == 0) {
 130                /*
 131                 * Ensure that this coredump name component can't cause the
 132                 * resulting corefile path to consist of a ".." or ".".
 133                 */
 134                if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
 135                                (cn->used - cur == 2 && cn->corename[cur] == '.'
 136                                && cn->corename[cur+1] == '.'))
 137                        cn->corename[cur] = '!';
 138
 139                /*
 140                 * Empty names are fishy and could be used to create a "//" in a
 141                 * corefile name, causing the coredump to happen one directory
 142                 * level too high. Enforce that all components of the core
 143                 * pattern are at least one character long.
 144                 */
 145                if (cn->used == cur)
 146                        ret = cn_printf(cn, "!");
 147        }
 148
 149        for (; cur < cn->used; ++cur) {
 150                if (cn->corename[cur] == '/')
 151                        cn->corename[cur] = '!';
 152        }
 153        return ret;
 154}
 155
 156static int cn_print_exe_file(struct core_name *cn, bool name_only)
 157{
 158        struct file *exe_file;
 159        char *pathbuf, *path, *ptr;
 160        int ret;
 161
 162        exe_file = get_mm_exe_file(current->mm);
 163        if (!exe_file)
 164                return cn_esc_printf(cn, "%s (path unknown)", current->comm);
 165
 166        pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
 167        if (!pathbuf) {
 168                ret = -ENOMEM;
 169                goto put_exe_file;
 170        }
 171
 172        path = file_path(exe_file, pathbuf, PATH_MAX);
 173        if (IS_ERR(path)) {
 174                ret = PTR_ERR(path);
 175                goto free_buf;
 176        }
 177
 178        if (name_only) {
 179                ptr = strrchr(path, '/');
 180                if (ptr)
 181                        path = ptr + 1;
 182        }
 183        ret = cn_esc_printf(cn, "%s", path);
 184
 185free_buf:
 186        kfree(pathbuf);
 187put_exe_file:
 188        fput(exe_file);
 189        return ret;
 190}
 191
 192/* format_corename will inspect the pattern parameter, and output a
 193 * name into corename, which must have space for at least
 194 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
 195 */
 196static int format_corename(struct core_name *cn, struct coredump_params *cprm,
 197                           size_t **argv, int *argc)
 198{
 199        const struct cred *cred = current_cred();
 200        const char *pat_ptr = core_pattern;
 201        int ispipe = (*pat_ptr == '|');
 202        bool was_space = false;
 203        int pid_in_pattern = 0;
 204        int err = 0;
 205
 206        cn->used = 0;
 207        cn->corename = NULL;
 208        if (expand_corename(cn, core_name_size))
 209                return -ENOMEM;
 210        cn->corename[0] = '\0';
 211
 212        if (ispipe) {
 213                int argvs = sizeof(core_pattern) / 2;
 214                (*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
 215                if (!(*argv))
 216                        return -ENOMEM;
 217                (*argv)[(*argc)++] = 0;
 218                ++pat_ptr;
 219                if (!(*pat_ptr))
 220                        return -ENOMEM;
 221        }
 222
 223        /* Repeat as long as we have more pattern to process and more output
 224           space */
 225        while (*pat_ptr) {
 226                /*
 227                 * Split on spaces before doing template expansion so that
 228                 * %e and %E don't get split if they have spaces in them
 229                 */
 230                if (ispipe) {
 231                        if (isspace(*pat_ptr)) {
 232                                if (cn->used != 0)
 233                                        was_space = true;
 234                                pat_ptr++;
 235                                continue;
 236                        } else if (was_space) {
 237                                was_space = false;
 238                                err = cn_printf(cn, "%c", '\0');
 239                                if (err)
 240                                        return err;
 241                                (*argv)[(*argc)++] = cn->used;
 242                        }
 243                }
 244                if (*pat_ptr != '%') {
 245                        err = cn_printf(cn, "%c", *pat_ptr++);
 246                } else {
 247                        switch (*++pat_ptr) {
 248                        /* single % at the end, drop that */
 249                        case 0:
 250                                goto out;
 251                        /* Double percent, output one percent */
 252                        case '%':
 253                                err = cn_printf(cn, "%c", '%');
 254                                break;
 255                        /* pid */
 256                        case 'p':
 257                                pid_in_pattern = 1;
 258                                err = cn_printf(cn, "%d",
 259                                              task_tgid_vnr(current));
 260                                break;
 261                        /* global pid */
 262                        case 'P':
 263                                err = cn_printf(cn, "%d",
 264                                              task_tgid_nr(current));
 265                                break;
 266                        case 'i':
 267                                err = cn_printf(cn, "%d",
 268                                              task_pid_vnr(current));
 269                                break;
 270                        case 'I':
 271                                err = cn_printf(cn, "%d",
 272                                              task_pid_nr(current));
 273                                break;
 274                        /* uid */
 275                        case 'u':
 276                                err = cn_printf(cn, "%u",
 277                                                from_kuid(&init_user_ns,
 278                                                          cred->uid));
 279                                break;
 280                        /* gid */
 281                        case 'g':
 282                                err = cn_printf(cn, "%u",
 283                                                from_kgid(&init_user_ns,
 284                                                          cred->gid));
 285                                break;
 286                        case 'd':
 287                                err = cn_printf(cn, "%d",
 288                                        __get_dumpable(cprm->mm_flags));
 289                                break;
 290                        /* signal that caused the coredump */
 291                        case 's':
 292                                err = cn_printf(cn, "%d",
 293                                                cprm->siginfo->si_signo);
 294                                break;
 295                        /* UNIX time of coredump */
 296                        case 't': {
 297                                time64_t time;
 298
 299                                time = ktime_get_real_seconds();
 300                                err = cn_printf(cn, "%lld", time);
 301                                break;
 302                        }
 303                        /* hostname */
 304                        case 'h':
 305                                down_read(&uts_sem);
 306                                err = cn_esc_printf(cn, "%s",
 307                                              utsname()->nodename);
 308                                up_read(&uts_sem);
 309                                break;
 310                        /* executable, could be changed by prctl PR_SET_NAME etc */
 311                        case 'e':
 312                                err = cn_esc_printf(cn, "%s", current->comm);
 313                                break;
 314                        /* file name of executable */
 315                        case 'f':
 316                                err = cn_print_exe_file(cn, true);
 317                                break;
 318                        case 'E':
 319                                err = cn_print_exe_file(cn, false);
 320                                break;
 321                        /* core limit size */
 322                        case 'c':
 323                                err = cn_printf(cn, "%lu",
 324                                              rlimit(RLIMIT_CORE));
 325                                break;
 326                        default:
 327                                break;
 328                        }
 329                        ++pat_ptr;
 330                }
 331
 332                if (err)
 333                        return err;
 334        }
 335
 336out:
 337        /* Backward compatibility with core_uses_pid:
 338         *
 339         * If core_pattern does not include a %p (as is the default)
 340         * and core_uses_pid is set, then .%pid will be appended to
 341         * the filename. Do not do this for piped commands. */
 342        if (!ispipe && !pid_in_pattern && core_uses_pid) {
 343                err = cn_printf(cn, ".%d", task_tgid_vnr(current));
 344                if (err)
 345                        return err;
 346        }
 347        return ispipe;
 348}
 349
 350static int zap_process(struct task_struct *start, int exit_code, int flags)
 351{
 352        struct task_struct *t;
 353        int nr = 0;
 354
 355        /* ignore all signals except SIGKILL, see prepare_signal() */
 356        start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
 357        start->signal->group_exit_code = exit_code;
 358        start->signal->group_stop_count = 0;
 359
 360        for_each_thread(start, t) {
 361                task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
 362                if (t != current && t->mm) {
 363                        sigaddset(&t->pending.signal, SIGKILL);
 364                        signal_wake_up(t, 1);
 365                        nr++;
 366                }
 367        }
 368
 369        return nr;
 370}
 371
 372static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
 373                        struct core_state *core_state, int exit_code)
 374{
 375        struct task_struct *g, *p;
 376        unsigned long flags;
 377        int nr = -EAGAIN;
 378
 379        spin_lock_irq(&tsk->sighand->siglock);
 380        if (!signal_group_exit(tsk->signal)) {
 381                mm->core_state = core_state;
 382                tsk->signal->group_exit_task = tsk;
 383                nr = zap_process(tsk, exit_code, 0);
 384                clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
 385        }
 386        spin_unlock_irq(&tsk->sighand->siglock);
 387        if (unlikely(nr < 0))
 388                return nr;
 389
 390        tsk->flags |= PF_DUMPCORE;
 391        if (atomic_read(&mm->mm_users) == nr + 1)
 392                goto done;
 393        /*
 394         * We should find and kill all tasks which use this mm, and we should
 395         * count them correctly into ->nr_threads. We don't take tasklist
 396         * lock, but this is safe wrt:
 397         *
 398         * fork:
 399         *      None of sub-threads can fork after zap_process(leader). All
 400         *      processes which were created before this point should be
 401         *      visible to zap_threads() because copy_process() adds the new
 402         *      process to the tail of init_task.tasks list, and lock/unlock
 403         *      of ->siglock provides a memory barrier.
 404         *
 405         * do_exit:
 406         *      The caller holds mm->mmap_lock. This means that the task which
 407         *      uses this mm can't pass exit_mm(), so it can't exit or clear
 408         *      its ->mm.
 409         *
 410         * de_thread:
 411         *      It does list_replace_rcu(&leader->tasks, &current->tasks),
 412         *      we must see either old or new leader, this does not matter.
 413         *      However, it can change p->sighand, so lock_task_sighand(p)
 414         *      must be used. Since p->mm != NULL and we hold ->mmap_lock
 415         *      it can't fail.
 416         *
 417         *      Note also that "g" can be the old leader with ->mm == NULL
 418         *      and already unhashed and thus removed from ->thread_group.
 419         *      This is OK, __unhash_process()->list_del_rcu() does not
 420         *      clear the ->next pointer, we will find the new leader via
 421         *      next_thread().
 422         */
 423        rcu_read_lock();
 424        for_each_process(g) {
 425                if (g == tsk->group_leader)
 426                        continue;
 427                if (g->flags & PF_KTHREAD)
 428                        continue;
 429
 430                for_each_thread(g, p) {
 431                        if (unlikely(!p->mm))
 432                                continue;
 433                        if (unlikely(p->mm == mm)) {
 434                                lock_task_sighand(p, &flags);
 435                                nr += zap_process(p, exit_code,
 436                                                        SIGNAL_GROUP_EXIT);
 437                                unlock_task_sighand(p, &flags);
 438                        }
 439                        break;
 440                }
 441        }
 442        rcu_read_unlock();
 443done:
 444        atomic_set(&core_state->nr_threads, nr);
 445        return nr;
 446}
 447
 448static int coredump_wait(int exit_code, struct core_state *core_state)
 449{
 450        struct task_struct *tsk = current;
 451        struct mm_struct *mm = tsk->mm;
 452        int core_waiters = -EBUSY;
 453
 454        init_completion(&core_state->startup);
 455        core_state->dumper.task = tsk;
 456        core_state->dumper.next = NULL;
 457
 458        if (mmap_write_lock_killable(mm))
 459                return -EINTR;
 460
 461        if (!mm->core_state)
 462                core_waiters = zap_threads(tsk, mm, core_state, exit_code);
 463        mmap_write_unlock(mm);
 464
 465        if (core_waiters > 0) {
 466                struct core_thread *ptr;
 467
 468                freezer_do_not_count();
 469                wait_for_completion(&core_state->startup);
 470                freezer_count();
 471                /*
 472                 * Wait for all the threads to become inactive, so that
 473                 * all the thread context (extended register state, like
 474                 * fpu etc) gets copied to the memory.
 475                 */
 476                ptr = core_state->dumper.next;
 477                while (ptr != NULL) {
 478                        wait_task_inactive(ptr->task, 0);
 479                        ptr = ptr->next;
 480                }
 481        }
 482
 483        return core_waiters;
 484}
 485
 486static void coredump_finish(struct mm_struct *mm, bool core_dumped)
 487{
 488        struct core_thread *curr, *next;
 489        struct task_struct *task;
 490
 491        spin_lock_irq(&current->sighand->siglock);
 492        if (core_dumped && !__fatal_signal_pending(current))
 493                current->signal->group_exit_code |= 0x80;
 494        current->signal->group_exit_task = NULL;
 495        current->signal->flags = SIGNAL_GROUP_EXIT;
 496        spin_unlock_irq(&current->sighand->siglock);
 497
 498        next = mm->core_state->dumper.next;
 499        while ((curr = next) != NULL) {
 500                next = curr->next;
 501                task = curr->task;
 502                /*
 503                 * see exit_mm(), curr->task must not see
 504                 * ->task == NULL before we read ->next.
 505                 */
 506                smp_mb();
 507                curr->task = NULL;
 508                wake_up_process(task);
 509        }
 510
 511        mm->core_state = NULL;
 512}
 513
 514static bool dump_interrupted(void)
 515{
 516        /*
 517         * SIGKILL or freezing() interrupt the coredumping. Perhaps we
 518         * can do try_to_freeze() and check __fatal_signal_pending(),
 519         * but then we need to teach dump_write() to restart and clear
 520         * TIF_SIGPENDING.
 521         */
 522        return fatal_signal_pending(current) || freezing(current);
 523}
 524
 525static void wait_for_dump_helpers(struct file *file)
 526{
 527        struct pipe_inode_info *pipe = file->private_data;
 528
 529        pipe_lock(pipe);
 530        pipe->readers++;
 531        pipe->writers--;
 532        wake_up_interruptible_sync(&pipe->rd_wait);
 533        kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 534        pipe_unlock(pipe);
 535
 536        /*
 537         * We actually want wait_event_freezable() but then we need
 538         * to clear TIF_SIGPENDING and improve dump_interrupted().
 539         */
 540        wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
 541
 542        pipe_lock(pipe);
 543        pipe->readers--;
 544        pipe->writers++;
 545        pipe_unlock(pipe);
 546}
 547
 548/*
 549 * umh_pipe_setup
 550 * helper function to customize the process used
 551 * to collect the core in userspace.  Specifically
 552 * it sets up a pipe and installs it as fd 0 (stdin)
 553 * for the process.  Returns 0 on success, or
 554 * PTR_ERR on failure.
 555 * Note that it also sets the core limit to 1.  This
 556 * is a special value that we use to trap recursive
 557 * core dumps
 558 */
 559static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
 560{
 561        struct file *files[2];
 562        struct coredump_params *cp = (struct coredump_params *)info->data;
 563        int err = create_pipe_files(files, 0);
 564        if (err)
 565                return err;
 566
 567        cp->file = files[1];
 568
 569        err = replace_fd(0, files[0], 0);
 570        fput(files[0]);
 571        /* and disallow core files too */
 572        current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
 573
 574        return err;
 575}
 576
 577void do_coredump(const kernel_siginfo_t *siginfo)
 578{
 579        struct core_state core_state;
 580        struct core_name cn;
 581        struct mm_struct *mm = current->mm;
 582        struct linux_binfmt * binfmt;
 583        const struct cred *old_cred;
 584        struct cred *cred;
 585        int retval = 0;
 586        int ispipe;
 587        size_t *argv = NULL;
 588        int argc = 0;
 589        /* require nonrelative corefile path and be extra careful */
 590        bool need_suid_safe = false;
 591        bool core_dumped = false;
 592        static atomic_t core_dump_count = ATOMIC_INIT(0);
 593        struct coredump_params cprm = {
 594                .siginfo = siginfo,
 595                .regs = signal_pt_regs(),
 596                .limit = rlimit(RLIMIT_CORE),
 597                /*
 598                 * We must use the same mm->flags while dumping core to avoid
 599                 * inconsistency of bit flags, since this flag is not protected
 600                 * by any locks.
 601                 */
 602                .mm_flags = mm->flags,
 603        };
 604
 605        audit_core_dumps(siginfo->si_signo);
 606
 607        binfmt = mm->binfmt;
 608        if (!binfmt || !binfmt->core_dump)
 609                goto fail;
 610        if (!__get_dumpable(cprm.mm_flags))
 611                goto fail;
 612
 613        cred = prepare_creds();
 614        if (!cred)
 615                goto fail;
 616        /*
 617         * We cannot trust fsuid as being the "true" uid of the process
 618         * nor do we know its entire history. We only know it was tainted
 619         * so we dump it as root in mode 2, and only into a controlled
 620         * environment (pipe handler or fully qualified path).
 621         */
 622        if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
 623                /* Setuid core dump mode */
 624                cred->fsuid = GLOBAL_ROOT_UID;  /* Dump root private */
 625                need_suid_safe = true;
 626        }
 627
 628        retval = coredump_wait(siginfo->si_signo, &core_state);
 629        if (retval < 0)
 630                goto fail_creds;
 631
 632        old_cred = override_creds(cred);
 633
 634        ispipe = format_corename(&cn, &cprm, &argv, &argc);
 635
 636        if (ispipe) {
 637                int argi;
 638                int dump_count;
 639                char **helper_argv;
 640                struct subprocess_info *sub_info;
 641
 642                if (ispipe < 0) {
 643                        printk(KERN_WARNING "format_corename failed\n");
 644                        printk(KERN_WARNING "Aborting core\n");
 645                        goto fail_unlock;
 646                }
 647
 648                if (cprm.limit == 1) {
 649                        /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
 650                         *
 651                         * Normally core limits are irrelevant to pipes, since
 652                         * we're not writing to the file system, but we use
 653                         * cprm.limit of 1 here as a special value, this is a
 654                         * consistent way to catch recursive crashes.
 655                         * We can still crash if the core_pattern binary sets
 656                         * RLIM_CORE = !1, but it runs as root, and can do
 657                         * lots of stupid things.
 658                         *
 659                         * Note that we use task_tgid_vnr here to grab the pid
 660                         * of the process group leader.  That way we get the
 661                         * right pid if a thread in a multi-threaded
 662                         * core_pattern process dies.
 663                         */
 664                        printk(KERN_WARNING
 665                                "Process %d(%s) has RLIMIT_CORE set to 1\n",
 666                                task_tgid_vnr(current), current->comm);
 667                        printk(KERN_WARNING "Aborting core\n");
 668                        goto fail_unlock;
 669                }
 670                cprm.limit = RLIM_INFINITY;
 671
 672                dump_count = atomic_inc_return(&core_dump_count);
 673                if (core_pipe_limit && (core_pipe_limit < dump_count)) {
 674                        printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
 675                               task_tgid_vnr(current), current->comm);
 676                        printk(KERN_WARNING "Skipping core dump\n");
 677                        goto fail_dropcount;
 678                }
 679
 680                helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
 681                                            GFP_KERNEL);
 682                if (!helper_argv) {
 683                        printk(KERN_WARNING "%s failed to allocate memory\n",
 684                               __func__);
 685                        goto fail_dropcount;
 686                }
 687                for (argi = 0; argi < argc; argi++)
 688                        helper_argv[argi] = cn.corename + argv[argi];
 689                helper_argv[argi] = NULL;
 690
 691                retval = -ENOMEM;
 692                sub_info = call_usermodehelper_setup(helper_argv[0],
 693                                                helper_argv, NULL, GFP_KERNEL,
 694                                                umh_pipe_setup, NULL, &cprm);
 695                if (sub_info)
 696                        retval = call_usermodehelper_exec(sub_info,
 697                                                          UMH_WAIT_EXEC);
 698
 699                kfree(helper_argv);
 700                if (retval) {
 701                        printk(KERN_INFO "Core dump to |%s pipe failed\n",
 702                               cn.corename);
 703                        goto close_fail;
 704                }
 705        } else {
 706                struct user_namespace *mnt_userns;
 707                struct inode *inode;
 708                int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
 709                                 O_LARGEFILE | O_EXCL;
 710
 711                if (cprm.limit < binfmt->min_coredump)
 712                        goto fail_unlock;
 713
 714                if (need_suid_safe && cn.corename[0] != '/') {
 715                        printk(KERN_WARNING "Pid %d(%s) can only dump core "\
 716                                "to fully qualified path!\n",
 717                                task_tgid_vnr(current), current->comm);
 718                        printk(KERN_WARNING "Skipping core dump\n");
 719                        goto fail_unlock;
 720                }
 721
 722                /*
 723                 * Unlink the file if it exists unless this is a SUID
 724                 * binary - in that case, we're running around with root
 725                 * privs and don't want to unlink another user's coredump.
 726                 */
 727                if (!need_suid_safe) {
 728                        /*
 729                         * If it doesn't exist, that's fine. If there's some
 730                         * other problem, we'll catch it at the filp_open().
 731                         */
 732                        do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
 733                }
 734
 735                /*
 736                 * There is a race between unlinking and creating the
 737                 * file, but if that causes an EEXIST here, that's
 738                 * fine - another process raced with us while creating
 739                 * the corefile, and the other process won. To userspace,
 740                 * what matters is that at least one of the two processes
 741                 * writes its coredump successfully, not which one.
 742                 */
 743                if (need_suid_safe) {
 744                        /*
 745                         * Using user namespaces, normal user tasks can change
 746                         * their current->fs->root to point to arbitrary
 747                         * directories. Since the intention of the "only dump
 748                         * with a fully qualified path" rule is to control where
 749                         * coredumps may be placed using root privileges,
 750                         * current->fs->root must not be used. Instead, use the
 751                         * root directory of init_task.
 752                         */
 753                        struct path root;
 754
 755                        task_lock(&init_task);
 756                        get_fs_root(init_task.fs, &root);
 757                        task_unlock(&init_task);
 758                        cprm.file = file_open_root(&root, cn.corename,
 759                                                   open_flags, 0600);
 760                        path_put(&root);
 761                } else {
 762                        cprm.file = filp_open(cn.corename, open_flags, 0600);
 763                }
 764                if (IS_ERR(cprm.file))
 765                        goto fail_unlock;
 766
 767                inode = file_inode(cprm.file);
 768                if (inode->i_nlink > 1)
 769                        goto close_fail;
 770                if (d_unhashed(cprm.file->f_path.dentry))
 771                        goto close_fail;
 772                /*
 773                 * AK: actually i see no reason to not allow this for named
 774                 * pipes etc, but keep the previous behaviour for now.
 775                 */
 776                if (!S_ISREG(inode->i_mode))
 777                        goto close_fail;
 778                /*
 779                 * Don't dump core if the filesystem changed owner or mode
 780                 * of the file during file creation. This is an issue when
 781                 * a process dumps core while its cwd is e.g. on a vfat
 782                 * filesystem.
 783                 */
 784                mnt_userns = file_mnt_user_ns(cprm.file);
 785                if (!uid_eq(i_uid_into_mnt(mnt_userns, inode), current_fsuid()))
 786                        goto close_fail;
 787                if ((inode->i_mode & 0677) != 0600)
 788                        goto close_fail;
 789                if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
 790                        goto close_fail;
 791                if (do_truncate(mnt_userns, cprm.file->f_path.dentry,
 792                                0, 0, cprm.file))
 793                        goto close_fail;
 794        }
 795
 796        /* get us an unshared descriptor table; almost always a no-op */
 797        /* The cell spufs coredump code reads the file descriptor tables */
 798        retval = unshare_files();
 799        if (retval)
 800                goto close_fail;
 801        if (!dump_interrupted()) {
 802                /*
 803                 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
 804                 * have this set to NULL.
 805                 */
 806                if (!cprm.file) {
 807                        pr_info("Core dump to |%s disabled\n", cn.corename);
 808                        goto close_fail;
 809                }
 810                file_start_write(cprm.file);
 811                core_dumped = binfmt->core_dump(&cprm);
 812                /*
 813                 * Ensures that file size is big enough to contain the current
 814                 * file postion. This prevents gdb from complaining about
 815                 * a truncated file if the last "write" to the file was
 816                 * dump_skip.
 817                 */
 818                if (cprm.to_skip) {
 819                        cprm.to_skip--;
 820                        dump_emit(&cprm, "", 1);
 821                }
 822                file_end_write(cprm.file);
 823        }
 824        if (ispipe && core_pipe_limit)
 825                wait_for_dump_helpers(cprm.file);
 826close_fail:
 827        if (cprm.file)
 828                filp_close(cprm.file, NULL);
 829fail_dropcount:
 830        if (ispipe)
 831                atomic_dec(&core_dump_count);
 832fail_unlock:
 833        kfree(argv);
 834        kfree(cn.corename);
 835        coredump_finish(mm, core_dumped);
 836        revert_creds(old_cred);
 837fail_creds:
 838        put_cred(cred);
 839fail:
 840        return;
 841}
 842
 843/*
 844 * Core dumping helper functions.  These are the only things you should
 845 * do on a core-file: use only these functions to write out all the
 846 * necessary info.
 847 */
 848static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr)
 849{
 850        struct file *file = cprm->file;
 851        loff_t pos = file->f_pos;
 852        ssize_t n;
 853        if (cprm->written + nr > cprm->limit)
 854                return 0;
 855
 856
 857        if (dump_interrupted())
 858                return 0;
 859        n = __kernel_write(file, addr, nr, &pos);
 860        if (n != nr)
 861                return 0;
 862        file->f_pos = pos;
 863        cprm->written += n;
 864        cprm->pos += n;
 865
 866        return 1;
 867}
 868
 869static int __dump_skip(struct coredump_params *cprm, size_t nr)
 870{
 871        static char zeroes[PAGE_SIZE];
 872        struct file *file = cprm->file;
 873        if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
 874                if (dump_interrupted() ||
 875                    file->f_op->llseek(file, nr, SEEK_CUR) < 0)
 876                        return 0;
 877                cprm->pos += nr;
 878                return 1;
 879        } else {
 880                while (nr > PAGE_SIZE) {
 881                        if (!__dump_emit(cprm, zeroes, PAGE_SIZE))
 882                                return 0;
 883                        nr -= PAGE_SIZE;
 884                }
 885                return __dump_emit(cprm, zeroes, nr);
 886        }
 887}
 888
 889int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
 890{
 891        if (cprm->to_skip) {
 892                if (!__dump_skip(cprm, cprm->to_skip))
 893                        return 0;
 894                cprm->to_skip = 0;
 895        }
 896        return __dump_emit(cprm, addr, nr);
 897}
 898EXPORT_SYMBOL(dump_emit);
 899
 900void dump_skip_to(struct coredump_params *cprm, unsigned long pos)
 901{
 902        cprm->to_skip = pos - cprm->pos;
 903}
 904EXPORT_SYMBOL(dump_skip_to);
 905
 906void dump_skip(struct coredump_params *cprm, size_t nr)
 907{
 908        cprm->to_skip += nr;
 909}
 910EXPORT_SYMBOL(dump_skip);
 911
 912#ifdef CONFIG_ELF_CORE
 913int dump_user_range(struct coredump_params *cprm, unsigned long start,
 914                    unsigned long len)
 915{
 916        unsigned long addr;
 917
 918        for (addr = start; addr < start + len; addr += PAGE_SIZE) {
 919                struct page *page;
 920                int stop;
 921
 922                /*
 923                 * To avoid having to allocate page tables for virtual address
 924                 * ranges that have never been used yet, and also to make it
 925                 * easy to generate sparse core files, use a helper that returns
 926                 * NULL when encountering an empty page table entry that would
 927                 * otherwise have been filled with the zero page.
 928                 */
 929                page = get_dump_page(addr);
 930                if (page) {
 931                        void *kaddr = kmap_local_page(page);
 932
 933                        stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
 934                        kunmap_local(kaddr);
 935                        put_page(page);
 936                        if (stop)
 937                                return 0;
 938                } else {
 939                        dump_skip(cprm, PAGE_SIZE);
 940                }
 941        }
 942        return 1;
 943}
 944#endif
 945
 946int dump_align(struct coredump_params *cprm, int align)
 947{
 948        unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1);
 949        if (align & (align - 1))
 950                return 0;
 951        if (mod)
 952                cprm->to_skip += align - mod;
 953        return 1;
 954}
 955EXPORT_SYMBOL(dump_align);
 956
 957/*
 958 * The purpose of always_dump_vma() is to make sure that special kernel mappings
 959 * that are useful for post-mortem analysis are included in every core dump.
 960 * In that way we ensure that the core dump is fully interpretable later
 961 * without matching up the same kernel and hardware config to see what PC values
 962 * meant. These special mappings include - vDSO, vsyscall, and other
 963 * architecture specific mappings
 964 */
 965static bool always_dump_vma(struct vm_area_struct *vma)
 966{
 967        /* Any vsyscall mappings? */
 968        if (vma == get_gate_vma(vma->vm_mm))
 969                return true;
 970
 971        /*
 972         * Assume that all vmas with a .name op should always be dumped.
 973         * If this changes, a new vm_ops field can easily be added.
 974         */
 975        if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
 976                return true;
 977
 978        /*
 979         * arch_vma_name() returns non-NULL for special architecture mappings,
 980         * such as vDSO sections.
 981         */
 982        if (arch_vma_name(vma))
 983                return true;
 984
 985        return false;
 986}
 987
 988/*
 989 * Decide how much of @vma's contents should be included in a core dump.
 990 */
 991static unsigned long vma_dump_size(struct vm_area_struct *vma,
 992                                   unsigned long mm_flags)
 993{
 994#define FILTER(type)    (mm_flags & (1UL << MMF_DUMP_##type))
 995
 996        /* always dump the vdso and vsyscall sections */
 997        if (always_dump_vma(vma))
 998                goto whole;
 999
1000        if (vma->vm_flags & VM_DONTDUMP)
1001                return 0;
1002
1003        /* support for DAX */
1004        if (vma_is_dax(vma)) {
1005                if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
1006                        goto whole;
1007                if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
1008                        goto whole;
1009                return 0;
1010        }
1011
1012        /* Hugetlb memory check */
1013        if (is_vm_hugetlb_page(vma)) {
1014                if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
1015                        goto whole;
1016                if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
1017                        goto whole;
1018                return 0;
1019        }
1020
1021        /* Do not dump I/O mapped devices or special mappings */
1022        if (vma->vm_flags & VM_IO)
1023                return 0;
1024
1025        /* By default, dump shared memory if mapped from an anonymous file. */
1026        if (vma->vm_flags & VM_SHARED) {
1027                if (file_inode(vma->vm_file)->i_nlink == 0 ?
1028                    FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
1029                        goto whole;
1030                return 0;
1031        }
1032
1033        /* Dump segments that have been written to.  */
1034        if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
1035                goto whole;
1036        if (vma->vm_file == NULL)
1037                return 0;
1038
1039        if (FILTER(MAPPED_PRIVATE))
1040                goto whole;
1041
1042        /*
1043         * If this is the beginning of an executable file mapping,
1044         * dump the first page to aid in determining what was mapped here.
1045         */
1046        if (FILTER(ELF_HEADERS) &&
1047            vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ) &&
1048            (READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
1049                return PAGE_SIZE;
1050
1051#undef  FILTER
1052
1053        return 0;
1054
1055whole:
1056        return vma->vm_end - vma->vm_start;
1057}
1058
1059static struct vm_area_struct *first_vma(struct task_struct *tsk,
1060                                        struct vm_area_struct *gate_vma)
1061{
1062        struct vm_area_struct *ret = tsk->mm->mmap;
1063
1064        if (ret)
1065                return ret;
1066        return gate_vma;
1067}
1068
1069/*
1070 * Helper function for iterating across a vma list.  It ensures that the caller
1071 * will visit `gate_vma' prior to terminating the search.
1072 */
1073static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
1074                                       struct vm_area_struct *gate_vma)
1075{
1076        struct vm_area_struct *ret;
1077
1078        ret = this_vma->vm_next;
1079        if (ret)
1080                return ret;
1081        if (this_vma == gate_vma)
1082                return NULL;
1083        return gate_vma;
1084}
1085
1086/*
1087 * Under the mmap_lock, take a snapshot of relevant information about the task's
1088 * VMAs.
1089 */
1090int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
1091                      struct core_vma_metadata **vma_meta,
1092                      size_t *vma_data_size_ptr)
1093{
1094        struct vm_area_struct *vma, *gate_vma;
1095        struct mm_struct *mm = current->mm;
1096        int i;
1097        size_t vma_data_size = 0;
1098
1099        /*
1100         * Once the stack expansion code is fixed to not change VMA bounds
1101         * under mmap_lock in read mode, this can be changed to take the
1102         * mmap_lock in read mode.
1103         */
1104        if (mmap_write_lock_killable(mm))
1105                return -EINTR;
1106
1107        gate_vma = get_gate_vma(mm);
1108        *vma_count = mm->map_count + (gate_vma ? 1 : 0);
1109
1110        *vma_meta = kvmalloc_array(*vma_count, sizeof(**vma_meta), GFP_KERNEL);
1111        if (!*vma_meta) {
1112                mmap_write_unlock(mm);
1113                return -ENOMEM;
1114        }
1115
1116        for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
1117                        vma = next_vma(vma, gate_vma), i++) {
1118                struct core_vma_metadata *m = (*vma_meta) + i;
1119
1120                m->start = vma->vm_start;
1121                m->end = vma->vm_end;
1122                m->flags = vma->vm_flags;
1123                m->dump_size = vma_dump_size(vma, cprm->mm_flags);
1124
1125                vma_data_size += m->dump_size;
1126        }
1127
1128        mmap_write_unlock(mm);
1129
1130        if (WARN_ON(i != *vma_count))
1131                return -EFAULT;
1132
1133        *vma_data_size_ptr = vma_data_size;
1134        return 0;
1135}
1136
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