linux/fs/exec.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *  linux/fs/exec.c
   4 *
   5 *  Copyright (C) 1991, 1992  Linus Torvalds
   6 */
   7
   8/*
   9 * #!-checking implemented by tytso.
  10 */
  11/*
  12 * Demand-loading implemented 01.12.91 - no need to read anything but
  13 * the header into memory. The inode of the executable is put into
  14 * "current->executable", and page faults do the actual loading. Clean.
  15 *
  16 * Once more I can proudly say that linux stood up to being changed: it
  17 * was less than 2 hours work to get demand-loading completely implemented.
  18 *
  19 * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
  20 * current->executable is only used by the procfs.  This allows a dispatch
  21 * table to check for several different types  of binary formats.  We keep
  22 * trying until we recognize the file or we run out of supported binary
  23 * formats.
  24 */
  25
  26#include <linux/kernel_read_file.h>
  27#include <linux/slab.h>
  28#include <linux/file.h>
  29#include <linux/fdtable.h>
  30#include <linux/mm.h>
  31#include <linux/vmacache.h>
  32#include <linux/stat.h>
  33#include <linux/fcntl.h>
  34#include <linux/swap.h>
  35#include <linux/string.h>
  36#include <linux/init.h>
  37#include <linux/sched/mm.h>
  38#include <linux/sched/coredump.h>
  39#include <linux/sched/signal.h>
  40#include <linux/sched/numa_balancing.h>
  41#include <linux/sched/task.h>
  42#include <linux/pagemap.h>
  43#include <linux/perf_event.h>
  44#include <linux/highmem.h>
  45#include <linux/spinlock.h>
  46#include <linux/key.h>
  47#include <linux/personality.h>
  48#include <linux/binfmts.h>
  49#include <linux/utsname.h>
  50#include <linux/pid_namespace.h>
  51#include <linux/module.h>
  52#include <linux/namei.h>
  53#include <linux/mount.h>
  54#include <linux/security.h>
  55#include <linux/syscalls.h>
  56#include <linux/tsacct_kern.h>
  57#include <linux/cn_proc.h>
  58#include <linux/audit.h>
  59#include <linux/tracehook.h>
  60#include <linux/kmod.h>
  61#include <linux/fsnotify.h>
  62#include <linux/fs_struct.h>
  63#include <linux/oom.h>
  64#include <linux/compat.h>
  65#include <linux/vmalloc.h>
  66#include <linux/io_uring.h>
  67#include <linux/syscall_user_dispatch.h>
  68
  69#include <linux/uaccess.h>
  70#include <asm/mmu_context.h>
  71#include <asm/tlb.h>
  72
  73#include <trace/events/task.h>
  74#include "internal.h"
  75
  76#include <trace/events/sched.h>
  77
  78static int bprm_creds_from_file(struct linux_binprm *bprm);
  79
  80int suid_dumpable = 0;
  81
  82static LIST_HEAD(formats);
  83static DEFINE_RWLOCK(binfmt_lock);
  84
  85void __register_binfmt(struct linux_binfmt * fmt, int insert)
  86{
  87        write_lock(&binfmt_lock);
  88        insert ? list_add(&fmt->lh, &formats) :
  89                 list_add_tail(&fmt->lh, &formats);
  90        write_unlock(&binfmt_lock);
  91}
  92
  93EXPORT_SYMBOL(__register_binfmt);
  94
  95void unregister_binfmt(struct linux_binfmt * fmt)
  96{
  97        write_lock(&binfmt_lock);
  98        list_del(&fmt->lh);
  99        write_unlock(&binfmt_lock);
 100}
 101
 102EXPORT_SYMBOL(unregister_binfmt);
 103
 104static inline void put_binfmt(struct linux_binfmt * fmt)
 105{
 106        module_put(fmt->module);
 107}
 108
 109bool path_noexec(const struct path *path)
 110{
 111        return (path->mnt->mnt_flags & MNT_NOEXEC) ||
 112               (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
 113}
 114
 115#ifdef CONFIG_USELIB
 116/*
 117 * Note that a shared library must be both readable and executable due to
 118 * security reasons.
 119 *
 120 * Also note that we take the address to load from from the file itself.
 121 */
 122SYSCALL_DEFINE1(uselib, const char __user *, library)
 123{
 124        struct linux_binfmt *fmt;
 125        struct file *file;
 126        struct filename *tmp = getname(library);
 127        int error = PTR_ERR(tmp);
 128        static const struct open_flags uselib_flags = {
 129                .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 130                .acc_mode = MAY_READ | MAY_EXEC,
 131                .intent = LOOKUP_OPEN,
 132                .lookup_flags = LOOKUP_FOLLOW,
 133        };
 134
 135        if (IS_ERR(tmp))
 136                goto out;
 137
 138        file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
 139        putname(tmp);
 140        error = PTR_ERR(file);
 141        if (IS_ERR(file))
 142                goto out;
 143
 144        /*
 145         * may_open() has already checked for this, so it should be
 146         * impossible to trip now. But we need to be extra cautious
 147         * and check again at the very end too.
 148         */
 149        error = -EACCES;
 150        if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
 151                         path_noexec(&file->f_path)))
 152                goto exit;
 153
 154        fsnotify_open(file);
 155
 156        error = -ENOEXEC;
 157
 158        read_lock(&binfmt_lock);
 159        list_for_each_entry(fmt, &formats, lh) {
 160                if (!fmt->load_shlib)
 161                        continue;
 162                if (!try_module_get(fmt->module))
 163                        continue;
 164                read_unlock(&binfmt_lock);
 165                error = fmt->load_shlib(file);
 166                read_lock(&binfmt_lock);
 167                put_binfmt(fmt);
 168                if (error != -ENOEXEC)
 169                        break;
 170        }
 171        read_unlock(&binfmt_lock);
 172exit:
 173        fput(file);
 174out:
 175        return error;
 176}
 177#endif /* #ifdef CONFIG_USELIB */
 178
 179#ifdef CONFIG_MMU
 180/*
 181 * The nascent bprm->mm is not visible until exec_mmap() but it can
 182 * use a lot of memory, account these pages in current->mm temporary
 183 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
 184 * change the counter back via acct_arg_size(0).
 185 */
 186static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 187{
 188        struct mm_struct *mm = current->mm;
 189        long diff = (long)(pages - bprm->vma_pages);
 190
 191        if (!mm || !diff)
 192                return;
 193
 194        bprm->vma_pages = pages;
 195        add_mm_counter(mm, MM_ANONPAGES, diff);
 196}
 197
 198static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 199                int write)
 200{
 201        struct page *page;
 202        int ret;
 203        unsigned int gup_flags = FOLL_FORCE;
 204
 205#ifdef CONFIG_STACK_GROWSUP
 206        if (write) {
 207                ret = expand_downwards(bprm->vma, pos);
 208                if (ret < 0)
 209                        return NULL;
 210        }
 211#endif
 212
 213        if (write)
 214                gup_flags |= FOLL_WRITE;
 215
 216        /*
 217         * We are doing an exec().  'current' is the process
 218         * doing the exec and bprm->mm is the new process's mm.
 219         */
 220        ret = get_user_pages_remote(bprm->mm, pos, 1, gup_flags,
 221                        &page, NULL, NULL);
 222        if (ret <= 0)
 223                return NULL;
 224
 225        if (write)
 226                acct_arg_size(bprm, vma_pages(bprm->vma));
 227
 228        return page;
 229}
 230
 231static void put_arg_page(struct page *page)
 232{
 233        put_page(page);
 234}
 235
 236static void free_arg_pages(struct linux_binprm *bprm)
 237{
 238}
 239
 240static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 241                struct page *page)
 242{
 243        flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 244}
 245
 246static int __bprm_mm_init(struct linux_binprm *bprm)
 247{
 248        int err;
 249        struct vm_area_struct *vma = NULL;
 250        struct mm_struct *mm = bprm->mm;
 251
 252        bprm->vma = vma = vm_area_alloc(mm);
 253        if (!vma)
 254                return -ENOMEM;
 255        vma_set_anonymous(vma);
 256
 257        if (mmap_write_lock_killable(mm)) {
 258                err = -EINTR;
 259                goto err_free;
 260        }
 261
 262        /*
 263         * Place the stack at the largest stack address the architecture
 264         * supports. Later, we'll move this to an appropriate place. We don't
 265         * use STACK_TOP because that can depend on attributes which aren't
 266         * configured yet.
 267         */
 268        BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 269        vma->vm_end = STACK_TOP_MAX;
 270        vma->vm_start = vma->vm_end - PAGE_SIZE;
 271        vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 272        vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 273
 274        err = insert_vm_struct(mm, vma);
 275        if (err)
 276                goto err;
 277
 278        mm->stack_vm = mm->total_vm = 1;
 279        mmap_write_unlock(mm);
 280        bprm->p = vma->vm_end - sizeof(void *);
 281        return 0;
 282err:
 283        mmap_write_unlock(mm);
 284err_free:
 285        bprm->vma = NULL;
 286        vm_area_free(vma);
 287        return err;
 288}
 289
 290static bool valid_arg_len(struct linux_binprm *bprm, long len)
 291{
 292        return len <= MAX_ARG_STRLEN;
 293}
 294
 295#else
 296
 297static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 298{
 299}
 300
 301static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 302                int write)
 303{
 304        struct page *page;
 305
 306        page = bprm->page[pos / PAGE_SIZE];
 307        if (!page && write) {
 308                page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 309                if (!page)
 310                        return NULL;
 311                bprm->page[pos / PAGE_SIZE] = page;
 312        }
 313
 314        return page;
 315}
 316
 317static void put_arg_page(struct page *page)
 318{
 319}
 320
 321static void free_arg_page(struct linux_binprm *bprm, int i)
 322{
 323        if (bprm->page[i]) {
 324                __free_page(bprm->page[i]);
 325                bprm->page[i] = NULL;
 326        }
 327}
 328
 329static void free_arg_pages(struct linux_binprm *bprm)
 330{
 331        int i;
 332
 333        for (i = 0; i < MAX_ARG_PAGES; i++)
 334                free_arg_page(bprm, i);
 335}
 336
 337static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 338                struct page *page)
 339{
 340}
 341
 342static int __bprm_mm_init(struct linux_binprm *bprm)
 343{
 344        bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 345        return 0;
 346}
 347
 348static bool valid_arg_len(struct linux_binprm *bprm, long len)
 349{
 350        return len <= bprm->p;
 351}
 352
 353#endif /* CONFIG_MMU */
 354
 355/*
 356 * Create a new mm_struct and populate it with a temporary stack
 357 * vm_area_struct.  We don't have enough context at this point to set the stack
 358 * flags, permissions, and offset, so we use temporary values.  We'll update
 359 * them later in setup_arg_pages().
 360 */
 361static int bprm_mm_init(struct linux_binprm *bprm)
 362{
 363        int err;
 364        struct mm_struct *mm = NULL;
 365
 366        bprm->mm = mm = mm_alloc();
 367        err = -ENOMEM;
 368        if (!mm)
 369                goto err;
 370
 371        /* Save current stack limit for all calculations made during exec. */
 372        task_lock(current->group_leader);
 373        bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
 374        task_unlock(current->group_leader);
 375
 376        err = __bprm_mm_init(bprm);
 377        if (err)
 378                goto err;
 379
 380        return 0;
 381
 382err:
 383        if (mm) {
 384                bprm->mm = NULL;
 385                mmdrop(mm);
 386        }
 387
 388        return err;
 389}
 390
 391struct user_arg_ptr {
 392#ifdef CONFIG_COMPAT
 393        bool is_compat;
 394#endif
 395        union {
 396                const char __user *const __user *native;
 397#ifdef CONFIG_COMPAT
 398                const compat_uptr_t __user *compat;
 399#endif
 400        } ptr;
 401};
 402
 403static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
 404{
 405        const char __user *native;
 406
 407#ifdef CONFIG_COMPAT
 408        if (unlikely(argv.is_compat)) {
 409                compat_uptr_t compat;
 410
 411                if (get_user(compat, argv.ptr.compat + nr))
 412                        return ERR_PTR(-EFAULT);
 413
 414                return compat_ptr(compat);
 415        }
 416#endif
 417
 418        if (get_user(native, argv.ptr.native + nr))
 419                return ERR_PTR(-EFAULT);
 420
 421        return native;
 422}
 423
 424/*
 425 * count() counts the number of strings in array ARGV.
 426 */
 427static int count(struct user_arg_ptr argv, int max)
 428{
 429        int i = 0;
 430
 431        if (argv.ptr.native != NULL) {
 432                for (;;) {
 433                        const char __user *p = get_user_arg_ptr(argv, i);
 434
 435                        if (!p)
 436                                break;
 437
 438                        if (IS_ERR(p))
 439                                return -EFAULT;
 440
 441                        if (i >= max)
 442                                return -E2BIG;
 443                        ++i;
 444
 445                        if (fatal_signal_pending(current))
 446                                return -ERESTARTNOHAND;
 447                        cond_resched();
 448                }
 449        }
 450        return i;
 451}
 452
 453static int count_strings_kernel(const char *const *argv)
 454{
 455        int i;
 456
 457        if (!argv)
 458                return 0;
 459
 460        for (i = 0; argv[i]; ++i) {
 461                if (i >= MAX_ARG_STRINGS)
 462                        return -E2BIG;
 463                if (fatal_signal_pending(current))
 464                        return -ERESTARTNOHAND;
 465                cond_resched();
 466        }
 467        return i;
 468}
 469
 470static int bprm_stack_limits(struct linux_binprm *bprm)
 471{
 472        unsigned long limit, ptr_size;
 473
 474        /*
 475         * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
 476         * (whichever is smaller) for the argv+env strings.
 477         * This ensures that:
 478         *  - the remaining binfmt code will not run out of stack space,
 479         *  - the program will have a reasonable amount of stack left
 480         *    to work from.
 481         */
 482        limit = _STK_LIM / 4 * 3;
 483        limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
 484        /*
 485         * We've historically supported up to 32 pages (ARG_MAX)
 486         * of argument strings even with small stacks
 487         */
 488        limit = max_t(unsigned long, limit, ARG_MAX);
 489        /*
 490         * We must account for the size of all the argv and envp pointers to
 491         * the argv and envp strings, since they will also take up space in
 492         * the stack. They aren't stored until much later when we can't
 493         * signal to the parent that the child has run out of stack space.
 494         * Instead, calculate it here so it's possible to fail gracefully.
 495         */
 496        ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
 497        if (limit <= ptr_size)
 498                return -E2BIG;
 499        limit -= ptr_size;
 500
 501        bprm->argmin = bprm->p - limit;
 502        return 0;
 503}
 504
 505/*
 506 * 'copy_strings()' copies argument/environment strings from the old
 507 * processes's memory to the new process's stack.  The call to get_user_pages()
 508 * ensures the destination page is created and not swapped out.
 509 */
 510static int copy_strings(int argc, struct user_arg_ptr argv,
 511                        struct linux_binprm *bprm)
 512{
 513        struct page *kmapped_page = NULL;
 514        char *kaddr = NULL;
 515        unsigned long kpos = 0;
 516        int ret;
 517
 518        while (argc-- > 0) {
 519                const char __user *str;
 520                int len;
 521                unsigned long pos;
 522
 523                ret = -EFAULT;
 524                str = get_user_arg_ptr(argv, argc);
 525                if (IS_ERR(str))
 526                        goto out;
 527
 528                len = strnlen_user(str, MAX_ARG_STRLEN);
 529                if (!len)
 530                        goto out;
 531
 532                ret = -E2BIG;
 533                if (!valid_arg_len(bprm, len))
 534                        goto out;
 535
 536                /* We're going to work our way backwords. */
 537                pos = bprm->p;
 538                str += len;
 539                bprm->p -= len;
 540#ifdef CONFIG_MMU
 541                if (bprm->p < bprm->argmin)
 542                        goto out;
 543#endif
 544
 545                while (len > 0) {
 546                        int offset, bytes_to_copy;
 547
 548                        if (fatal_signal_pending(current)) {
 549                                ret = -ERESTARTNOHAND;
 550                                goto out;
 551                        }
 552                        cond_resched();
 553
 554                        offset = pos % PAGE_SIZE;
 555                        if (offset == 0)
 556                                offset = PAGE_SIZE;
 557
 558                        bytes_to_copy = offset;
 559                        if (bytes_to_copy > len)
 560                                bytes_to_copy = len;
 561
 562                        offset -= bytes_to_copy;
 563                        pos -= bytes_to_copy;
 564                        str -= bytes_to_copy;
 565                        len -= bytes_to_copy;
 566
 567                        if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 568                                struct page *page;
 569
 570                                page = get_arg_page(bprm, pos, 1);
 571                                if (!page) {
 572                                        ret = -E2BIG;
 573                                        goto out;
 574                                }
 575
 576                                if (kmapped_page) {
 577                                        flush_kernel_dcache_page(kmapped_page);
 578                                        kunmap(kmapped_page);
 579                                        put_arg_page(kmapped_page);
 580                                }
 581                                kmapped_page = page;
 582                                kaddr = kmap(kmapped_page);
 583                                kpos = pos & PAGE_MASK;
 584                                flush_arg_page(bprm, kpos, kmapped_page);
 585                        }
 586                        if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 587                                ret = -EFAULT;
 588                                goto out;
 589                        }
 590                }
 591        }
 592        ret = 0;
 593out:
 594        if (kmapped_page) {
 595                flush_kernel_dcache_page(kmapped_page);
 596                kunmap(kmapped_page);
 597                put_arg_page(kmapped_page);
 598        }
 599        return ret;
 600}
 601
 602/*
 603 * Copy and argument/environment string from the kernel to the processes stack.
 604 */
 605int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
 606{
 607        int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
 608        unsigned long pos = bprm->p;
 609
 610        if (len == 0)
 611                return -EFAULT;
 612        if (!valid_arg_len(bprm, len))
 613                return -E2BIG;
 614
 615        /* We're going to work our way backwards. */
 616        arg += len;
 617        bprm->p -= len;
 618        if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin)
 619                return -E2BIG;
 620
 621        while (len > 0) {
 622                unsigned int bytes_to_copy = min_t(unsigned int, len,
 623                                min_not_zero(offset_in_page(pos), PAGE_SIZE));
 624                struct page *page;
 625                char *kaddr;
 626
 627                pos -= bytes_to_copy;
 628                arg -= bytes_to_copy;
 629                len -= bytes_to_copy;
 630
 631                page = get_arg_page(bprm, pos, 1);
 632                if (!page)
 633                        return -E2BIG;
 634                kaddr = kmap_atomic(page);
 635                flush_arg_page(bprm, pos & PAGE_MASK, page);
 636                memcpy(kaddr + offset_in_page(pos), arg, bytes_to_copy);
 637                flush_kernel_dcache_page(page);
 638                kunmap_atomic(kaddr);
 639                put_arg_page(page);
 640        }
 641
 642        return 0;
 643}
 644EXPORT_SYMBOL(copy_string_kernel);
 645
 646static int copy_strings_kernel(int argc, const char *const *argv,
 647                               struct linux_binprm *bprm)
 648{
 649        while (argc-- > 0) {
 650                int ret = copy_string_kernel(argv[argc], bprm);
 651                if (ret < 0)
 652                        return ret;
 653                if (fatal_signal_pending(current))
 654                        return -ERESTARTNOHAND;
 655                cond_resched();
 656        }
 657        return 0;
 658}
 659
 660#ifdef CONFIG_MMU
 661
 662/*
 663 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 664 * the binfmt code determines where the new stack should reside, we shift it to
 665 * its final location.  The process proceeds as follows:
 666 *
 667 * 1) Use shift to calculate the new vma endpoints.
 668 * 2) Extend vma to cover both the old and new ranges.  This ensures the
 669 *    arguments passed to subsequent functions are consistent.
 670 * 3) Move vma's page tables to the new range.
 671 * 4) Free up any cleared pgd range.
 672 * 5) Shrink the vma to cover only the new range.
 673 */
 674static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 675{
 676        struct mm_struct *mm = vma->vm_mm;
 677        unsigned long old_start = vma->vm_start;
 678        unsigned long old_end = vma->vm_end;
 679        unsigned long length = old_end - old_start;
 680        unsigned long new_start = old_start - shift;
 681        unsigned long new_end = old_end - shift;
 682        struct mmu_gather tlb;
 683
 684        BUG_ON(new_start > new_end);
 685
 686        /*
 687         * ensure there are no vmas between where we want to go
 688         * and where we are
 689         */
 690        if (vma != find_vma(mm, new_start))
 691                return -EFAULT;
 692
 693        /*
 694         * cover the whole range: [new_start, old_end)
 695         */
 696        if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
 697                return -ENOMEM;
 698
 699        /*
 700         * move the page tables downwards, on failure we rely on
 701         * process cleanup to remove whatever mess we made.
 702         */
 703        if (length != move_page_tables(vma, old_start,
 704                                       vma, new_start, length, false))
 705                return -ENOMEM;
 706
 707        lru_add_drain();
 708        tlb_gather_mmu(&tlb, mm);
 709        if (new_end > old_start) {
 710                /*
 711                 * when the old and new regions overlap clear from new_end.
 712                 */
 713                free_pgd_range(&tlb, new_end, old_end, new_end,
 714                        vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 715        } else {
 716                /*
 717                 * otherwise, clean from old_start; this is done to not touch
 718                 * the address space in [new_end, old_start) some architectures
 719                 * have constraints on va-space that make this illegal (IA64) -
 720                 * for the others its just a little faster.
 721                 */
 722                free_pgd_range(&tlb, old_start, old_end, new_end,
 723                        vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 724        }
 725        tlb_finish_mmu(&tlb);
 726
 727        /*
 728         * Shrink the vma to just the new range.  Always succeeds.
 729         */
 730        vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 731
 732        return 0;
 733}
 734
 735/*
 736 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 737 * the stack is optionally relocated, and some extra space is added.
 738 */
 739int setup_arg_pages(struct linux_binprm *bprm,
 740                    unsigned long stack_top,
 741                    int executable_stack)
 742{
 743        unsigned long ret;
 744        unsigned long stack_shift;
 745        struct mm_struct *mm = current->mm;
 746        struct vm_area_struct *vma = bprm->vma;
 747        struct vm_area_struct *prev = NULL;
 748        unsigned long vm_flags;
 749        unsigned long stack_base;
 750        unsigned long stack_size;
 751        unsigned long stack_expand;
 752        unsigned long rlim_stack;
 753
 754#ifdef CONFIG_STACK_GROWSUP
 755        /* Limit stack size */
 756        stack_base = bprm->rlim_stack.rlim_max;
 757
 758        stack_base = calc_max_stack_size(stack_base);
 759
 760        /* Add space for stack randomization. */
 761        stack_base += (STACK_RND_MASK << PAGE_SHIFT);
 762
 763        /* Make sure we didn't let the argument array grow too large. */
 764        if (vma->vm_end - vma->vm_start > stack_base)
 765                return -ENOMEM;
 766
 767        stack_base = PAGE_ALIGN(stack_top - stack_base);
 768
 769        stack_shift = vma->vm_start - stack_base;
 770        mm->arg_start = bprm->p - stack_shift;
 771        bprm->p = vma->vm_end - stack_shift;
 772#else
 773        stack_top = arch_align_stack(stack_top);
 774        stack_top = PAGE_ALIGN(stack_top);
 775
 776        if (unlikely(stack_top < mmap_min_addr) ||
 777            unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 778                return -ENOMEM;
 779
 780        stack_shift = vma->vm_end - stack_top;
 781
 782        bprm->p -= stack_shift;
 783        mm->arg_start = bprm->p;
 784#endif
 785
 786        if (bprm->loader)
 787                bprm->loader -= stack_shift;
 788        bprm->exec -= stack_shift;
 789
 790        if (mmap_write_lock_killable(mm))
 791                return -EINTR;
 792
 793        vm_flags = VM_STACK_FLAGS;
 794
 795        /*
 796         * Adjust stack execute permissions; explicitly enable for
 797         * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 798         * (arch default) otherwise.
 799         */
 800        if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 801                vm_flags |= VM_EXEC;
 802        else if (executable_stack == EXSTACK_DISABLE_X)
 803                vm_flags &= ~VM_EXEC;
 804        vm_flags |= mm->def_flags;
 805        vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 806
 807        ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 808                        vm_flags);
 809        if (ret)
 810                goto out_unlock;
 811        BUG_ON(prev != vma);
 812
 813        if (unlikely(vm_flags & VM_EXEC)) {
 814                pr_warn_once("process '%pD4' started with executable stack\n",
 815                             bprm->file);
 816        }
 817
 818        /* Move stack pages down in memory. */
 819        if (stack_shift) {
 820                ret = shift_arg_pages(vma, stack_shift);
 821                if (ret)
 822                        goto out_unlock;
 823        }
 824
 825        /* mprotect_fixup is overkill to remove the temporary stack flags */
 826        vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
 827
 828        stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
 829        stack_size = vma->vm_end - vma->vm_start;
 830        /*
 831         * Align this down to a page boundary as expand_stack
 832         * will align it up.
 833         */
 834        rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
 835#ifdef CONFIG_STACK_GROWSUP
 836        if (stack_size + stack_expand > rlim_stack)
 837                stack_base = vma->vm_start + rlim_stack;
 838        else
 839                stack_base = vma->vm_end + stack_expand;
 840#else
 841        if (stack_size + stack_expand > rlim_stack)
 842                stack_base = vma->vm_end - rlim_stack;
 843        else
 844                stack_base = vma->vm_start - stack_expand;
 845#endif
 846        current->mm->start_stack = bprm->p;
 847        ret = expand_stack(vma, stack_base);
 848        if (ret)
 849                ret = -EFAULT;
 850
 851out_unlock:
 852        mmap_write_unlock(mm);
 853        return ret;
 854}
 855EXPORT_SYMBOL(setup_arg_pages);
 856
 857#else
 858
 859/*
 860 * Transfer the program arguments and environment from the holding pages
 861 * onto the stack. The provided stack pointer is adjusted accordingly.
 862 */
 863int transfer_args_to_stack(struct linux_binprm *bprm,
 864                           unsigned long *sp_location)
 865{
 866        unsigned long index, stop, sp;
 867        int ret = 0;
 868
 869        stop = bprm->p >> PAGE_SHIFT;
 870        sp = *sp_location;
 871
 872        for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
 873                unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
 874                char *src = kmap(bprm->page[index]) + offset;
 875                sp -= PAGE_SIZE - offset;
 876                if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
 877                        ret = -EFAULT;
 878                kunmap(bprm->page[index]);
 879                if (ret)
 880                        goto out;
 881        }
 882
 883        *sp_location = sp;
 884
 885out:
 886        return ret;
 887}
 888EXPORT_SYMBOL(transfer_args_to_stack);
 889
 890#endif /* CONFIG_MMU */
 891
 892static struct file *do_open_execat(int fd, struct filename *name, int flags)
 893{
 894        struct file *file;
 895        int err;
 896        struct open_flags open_exec_flags = {
 897                .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 898                .acc_mode = MAY_EXEC,
 899                .intent = LOOKUP_OPEN,
 900                .lookup_flags = LOOKUP_FOLLOW,
 901        };
 902
 903        if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 904                return ERR_PTR(-EINVAL);
 905        if (flags & AT_SYMLINK_NOFOLLOW)
 906                open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
 907        if (flags & AT_EMPTY_PATH)
 908                open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
 909
 910        file = do_filp_open(fd, name, &open_exec_flags);
 911        if (IS_ERR(file))
 912                goto out;
 913
 914        /*
 915         * may_open() has already checked for this, so it should be
 916         * impossible to trip now. But we need to be extra cautious
 917         * and check again at the very end too.
 918         */
 919        err = -EACCES;
 920        if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
 921                         path_noexec(&file->f_path)))
 922                goto exit;
 923
 924        err = deny_write_access(file);
 925        if (err)
 926                goto exit;
 927
 928        if (name->name[0] != '\0')
 929                fsnotify_open(file);
 930
 931out:
 932        return file;
 933
 934exit:
 935        fput(file);
 936        return ERR_PTR(err);
 937}
 938
 939struct file *open_exec(const char *name)
 940{
 941        struct filename *filename = getname_kernel(name);
 942        struct file *f = ERR_CAST(filename);
 943
 944        if (!IS_ERR(filename)) {
 945                f = do_open_execat(AT_FDCWD, filename, 0);
 946                putname(filename);
 947        }
 948        return f;
 949}
 950EXPORT_SYMBOL(open_exec);
 951
 952#if defined(CONFIG_HAVE_AOUT) || defined(CONFIG_BINFMT_FLAT) || \
 953    defined(CONFIG_BINFMT_ELF_FDPIC)
 954ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
 955{
 956        ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
 957        if (res > 0)
 958                flush_icache_user_range(addr, addr + len);
 959        return res;
 960}
 961EXPORT_SYMBOL(read_code);
 962#endif
 963
 964/*
 965 * Maps the mm_struct mm into the current task struct.
 966 * On success, this function returns with exec_update_lock
 967 * held for writing.
 968 */
 969static int exec_mmap(struct mm_struct *mm)
 970{
 971        struct task_struct *tsk;
 972        struct mm_struct *old_mm, *active_mm;
 973        int ret;
 974
 975        /* Notify parent that we're no longer interested in the old VM */
 976        tsk = current;
 977        old_mm = current->mm;
 978        exec_mm_release(tsk, old_mm);
 979        if (old_mm)
 980                sync_mm_rss(old_mm);
 981
 982        ret = down_write_killable(&tsk->signal->exec_update_lock);
 983        if (ret)
 984                return ret;
 985
 986        if (old_mm) {
 987                /*
 988                 * Make sure that if there is a core dump in progress
 989                 * for the old mm, we get out and die instead of going
 990                 * through with the exec.  We must hold mmap_lock around
 991                 * checking core_state and changing tsk->mm.
 992                 */
 993                mmap_read_lock(old_mm);
 994                if (unlikely(old_mm->core_state)) {
 995                        mmap_read_unlock(old_mm);
 996                        up_write(&tsk->signal->exec_update_lock);
 997                        return -EINTR;
 998                }
 999        }
1000
1001        task_lock(tsk);
1002        membarrier_exec_mmap(mm);
1003
1004        local_irq_disable();
1005        active_mm = tsk->active_mm;
1006        tsk->active_mm = mm;
1007        tsk->mm = mm;
1008        /*
1009         * This prevents preemption while active_mm is being loaded and
1010         * it and mm are being updated, which could cause problems for
1011         * lazy tlb mm refcounting when these are updated by context
1012         * switches. Not all architectures can handle irqs off over
1013         * activate_mm yet.
1014         */
1015        if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
1016                local_irq_enable();
1017        activate_mm(active_mm, mm);
1018        if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
1019                local_irq_enable();
1020        tsk->mm->vmacache_seqnum = 0;
1021        vmacache_flush(tsk);
1022        task_unlock(tsk);
1023        if (old_mm) {
1024                mmap_read_unlock(old_mm);
1025                BUG_ON(active_mm != old_mm);
1026                setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
1027                mm_update_next_owner(old_mm);
1028                mmput(old_mm);
1029                return 0;
1030        }
1031        mmdrop(active_mm);
1032        return 0;
1033}
1034
1035static int de_thread(struct task_struct *tsk)
1036{
1037        struct signal_struct *sig = tsk->signal;
1038        struct sighand_struct *oldsighand = tsk->sighand;
1039        spinlock_t *lock = &oldsighand->siglock;
1040
1041        if (thread_group_empty(tsk))
1042                goto no_thread_group;
1043
1044        /*
1045         * Kill all other threads in the thread group.
1046         */
1047        spin_lock_irq(lock);
1048        if (signal_group_exit(sig)) {
1049                /*
1050                 * Another group action in progress, just
1051                 * return so that the signal is processed.
1052                 */
1053                spin_unlock_irq(lock);
1054                return -EAGAIN;
1055        }
1056
1057        sig->group_exit_task = tsk;
1058        sig->notify_count = zap_other_threads(tsk);
1059        if (!thread_group_leader(tsk))
1060                sig->notify_count--;
1061
1062        while (sig->notify_count) {
1063                __set_current_state(TASK_KILLABLE);
1064                spin_unlock_irq(lock);
1065                schedule();
1066                if (__fatal_signal_pending(tsk))
1067                        goto killed;
1068                spin_lock_irq(lock);
1069        }
1070        spin_unlock_irq(lock);
1071
1072        /*
1073         * At this point all other threads have exited, all we have to
1074         * do is to wait for the thread group leader to become inactive,
1075         * and to assume its PID:
1076         */
1077        if (!thread_group_leader(tsk)) {
1078                struct task_struct *leader = tsk->group_leader;
1079
1080                for (;;) {
1081                        cgroup_threadgroup_change_begin(tsk);
1082                        write_lock_irq(&tasklist_lock);
1083                        /*
1084                         * Do this under tasklist_lock to ensure that
1085                         * exit_notify() can't miss ->group_exit_task
1086                         */
1087                        sig->notify_count = -1;
1088                        if (likely(leader->exit_state))
1089                                break;
1090                        __set_current_state(TASK_KILLABLE);
1091                        write_unlock_irq(&tasklist_lock);
1092                        cgroup_threadgroup_change_end(tsk);
1093                        schedule();
1094                        if (__fatal_signal_pending(tsk))
1095                                goto killed;
1096                }
1097
1098                /*
1099                 * The only record we have of the real-time age of a
1100                 * process, regardless of execs it's done, is start_time.
1101                 * All the past CPU time is accumulated in signal_struct
1102                 * from sister threads now dead.  But in this non-leader
1103                 * exec, nothing survives from the original leader thread,
1104                 * whose birth marks the true age of this process now.
1105                 * When we take on its identity by switching to its PID, we
1106                 * also take its birthdate (always earlier than our own).
1107                 */
1108                tsk->start_time = leader->start_time;
1109                tsk->start_boottime = leader->start_boottime;
1110
1111                BUG_ON(!same_thread_group(leader, tsk));
1112                /*
1113                 * An exec() starts a new thread group with the
1114                 * TGID of the previous thread group. Rehash the
1115                 * two threads with a switched PID, and release
1116                 * the former thread group leader:
1117                 */
1118
1119                /* Become a process group leader with the old leader's pid.
1120                 * The old leader becomes a thread of the this thread group.
1121                 */
1122                exchange_tids(tsk, leader);
1123                transfer_pid(leader, tsk, PIDTYPE_TGID);
1124                transfer_pid(leader, tsk, PIDTYPE_PGID);
1125                transfer_pid(leader, tsk, PIDTYPE_SID);
1126
1127                list_replace_rcu(&leader->tasks, &tsk->tasks);
1128                list_replace_init(&leader->sibling, &tsk->sibling);
1129
1130                tsk->group_leader = tsk;
1131                leader->group_leader = tsk;
1132
1133                tsk->exit_signal = SIGCHLD;
1134                leader->exit_signal = -1;
1135
1136                BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1137                leader->exit_state = EXIT_DEAD;
1138
1139                /*
1140                 * We are going to release_task()->ptrace_unlink() silently,
1141                 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1142                 * the tracer wont't block again waiting for this thread.
1143                 */
1144                if (unlikely(leader->ptrace))
1145                        __wake_up_parent(leader, leader->parent);
1146                write_unlock_irq(&tasklist_lock);
1147                cgroup_threadgroup_change_end(tsk);
1148
1149                release_task(leader);
1150        }
1151
1152        sig->group_exit_task = NULL;
1153        sig->notify_count = 0;
1154
1155no_thread_group:
1156        /* we have changed execution domain */
1157        tsk->exit_signal = SIGCHLD;
1158
1159        BUG_ON(!thread_group_leader(tsk));
1160        return 0;
1161
1162killed:
1163        /* protects against exit_notify() and __exit_signal() */
1164        read_lock(&tasklist_lock);
1165        sig->group_exit_task = NULL;
1166        sig->notify_count = 0;
1167        read_unlock(&tasklist_lock);
1168        return -EAGAIN;
1169}
1170
1171
1172/*
1173 * This function makes sure the current process has its own signal table,
1174 * so that flush_signal_handlers can later reset the handlers without
1175 * disturbing other processes.  (Other processes might share the signal
1176 * table via the CLONE_SIGHAND option to clone().)
1177 */
1178static int unshare_sighand(struct task_struct *me)
1179{
1180        struct sighand_struct *oldsighand = me->sighand;
1181
1182        if (refcount_read(&oldsighand->count) != 1) {
1183                struct sighand_struct *newsighand;
1184                /*
1185                 * This ->sighand is shared with the CLONE_SIGHAND
1186                 * but not CLONE_THREAD task, switch to the new one.
1187                 */
1188                newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1189                if (!newsighand)
1190                        return -ENOMEM;
1191
1192                refcount_set(&newsighand->count, 1);
1193                memcpy(newsighand->action, oldsighand->action,
1194                       sizeof(newsighand->action));
1195
1196                write_lock_irq(&tasklist_lock);
1197                spin_lock(&oldsighand->siglock);
1198                rcu_assign_pointer(me->sighand, newsighand);
1199                spin_unlock(&oldsighand->siglock);
1200                write_unlock_irq(&tasklist_lock);
1201
1202                __cleanup_sighand(oldsighand);
1203        }
1204        return 0;
1205}
1206
1207char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
1208{
1209        task_lock(tsk);
1210        strncpy(buf, tsk->comm, buf_size);
1211        task_unlock(tsk);
1212        return buf;
1213}
1214EXPORT_SYMBOL_GPL(__get_task_comm);
1215
1216/*
1217 * These functions flushes out all traces of the currently running executable
1218 * so that a new one can be started
1219 */
1220
1221void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1222{
1223        task_lock(tsk);
1224        trace_task_rename(tsk, buf);
1225        strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1226        task_unlock(tsk);
1227        perf_event_comm(tsk, exec);
1228}
1229
1230/*
1231 * Calling this is the point of no return. None of the failures will be
1232 * seen by userspace since either the process is already taking a fatal
1233 * signal (via de_thread() or coredump), or will have SEGV raised
1234 * (after exec_mmap()) by search_binary_handler (see below).
1235 */
1236int begin_new_exec(struct linux_binprm * bprm)
1237{
1238        struct task_struct *me = current;
1239        int retval;
1240
1241        /* Once we are committed compute the creds */
1242        retval = bprm_creds_from_file(bprm);
1243        if (retval)
1244                return retval;
1245
1246        /*
1247         * Ensure all future errors are fatal.
1248         */
1249        bprm->point_of_no_return = true;
1250
1251        /*
1252         * Make this the only thread in the thread group.
1253         */
1254        retval = de_thread(me);
1255        if (retval)
1256                goto out;
1257
1258        /*
1259         * Cancel any io_uring activity across execve
1260         */
1261        io_uring_task_cancel();
1262
1263        /* Ensure the files table is not shared. */
1264        retval = unshare_files();
1265        if (retval)
1266                goto out;
1267
1268        /*
1269         * Must be called _before_ exec_mmap() as bprm->mm is
1270         * not visibile until then. This also enables the update
1271         * to be lockless.
1272         */
1273        set_mm_exe_file(bprm->mm, bprm->file);
1274
1275        /* If the binary is not readable then enforce mm->dumpable=0 */
1276        would_dump(bprm, bprm->file);
1277        if (bprm->have_execfd)
1278                would_dump(bprm, bprm->executable);
1279
1280        /*
1281         * Release all of the old mmap stuff
1282         */
1283        acct_arg_size(bprm, 0);
1284        retval = exec_mmap(bprm->mm);
1285        if (retval)
1286                goto out;
1287
1288        bprm->mm = NULL;
1289
1290#ifdef CONFIG_POSIX_TIMERS
1291        exit_itimers(me->signal);
1292        flush_itimer_signals();
1293#endif
1294
1295        /*
1296         * Make the signal table private.
1297         */
1298        retval = unshare_sighand(me);
1299        if (retval)
1300                goto out_unlock;
1301
1302        /*
1303         * Ensure that the uaccess routines can actually operate on userspace
1304         * pointers:
1305         */
1306        force_uaccess_begin();
1307
1308        me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1309                                        PF_NOFREEZE | PF_NO_SETAFFINITY);
1310        flush_thread();
1311        me->personality &= ~bprm->per_clear;
1312
1313        clear_syscall_work_syscall_user_dispatch(me);
1314
1315        /*
1316         * We have to apply CLOEXEC before we change whether the process is
1317         * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1318         * trying to access the should-be-closed file descriptors of a process
1319         * undergoing exec(2).
1320         */
1321        do_close_on_exec(me->files);
1322
1323        if (bprm->secureexec) {
1324                /* Make sure parent cannot signal privileged process. */
1325                me->pdeath_signal = 0;
1326
1327                /*
1328                 * For secureexec, reset the stack limit to sane default to
1329                 * avoid bad behavior from the prior rlimits. This has to
1330                 * happen before arch_pick_mmap_layout(), which examines
1331                 * RLIMIT_STACK, but after the point of no return to avoid
1332                 * needing to clean up the change on failure.
1333                 */
1334                if (bprm->rlim_stack.rlim_cur > _STK_LIM)
1335                        bprm->rlim_stack.rlim_cur = _STK_LIM;
1336        }
1337
1338        me->sas_ss_sp = me->sas_ss_size = 0;
1339
1340        /*
1341         * Figure out dumpability. Note that this checking only of current
1342         * is wrong, but userspace depends on it. This should be testing
1343         * bprm->secureexec instead.
1344         */
1345        if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
1346            !(uid_eq(current_euid(), current_uid()) &&
1347              gid_eq(current_egid(), current_gid())))
1348                set_dumpable(current->mm, suid_dumpable);
1349        else
1350                set_dumpable(current->mm, SUID_DUMP_USER);
1351
1352        perf_event_exec();
1353        __set_task_comm(me, kbasename(bprm->filename), true);
1354
1355        /* An exec changes our domain. We are no longer part of the thread
1356           group */
1357        WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
1358        flush_signal_handlers(me, 0);
1359
1360        retval = set_cred_ucounts(bprm->cred);
1361        if (retval < 0)
1362                goto out_unlock;
1363
1364        /*
1365         * install the new credentials for this executable
1366         */
1367        security_bprm_committing_creds(bprm);
1368
1369        commit_creds(bprm->cred);
1370        bprm->cred = NULL;
1371
1372        /*
1373         * Disable monitoring for regular users
1374         * when executing setuid binaries. Must
1375         * wait until new credentials are committed
1376         * by commit_creds() above
1377         */
1378        if (get_dumpable(me->mm) != SUID_DUMP_USER)
1379                perf_event_exit_task(me);
1380        /*
1381         * cred_guard_mutex must be held at least to this point to prevent
1382         * ptrace_attach() from altering our determination of the task's
1383         * credentials; any time after this it may be unlocked.
1384         */
1385        security_bprm_committed_creds(bprm);
1386
1387        /* Pass the opened binary to the interpreter. */
1388        if (bprm->have_execfd) {
1389                retval = get_unused_fd_flags(0);
1390                if (retval < 0)
1391                        goto out_unlock;
1392                fd_install(retval, bprm->executable);
1393                bprm->executable = NULL;
1394                bprm->execfd = retval;
1395        }
1396        return 0;
1397
1398out_unlock:
1399        up_write(&me->signal->exec_update_lock);
1400out:
1401        return retval;
1402}
1403EXPORT_SYMBOL(begin_new_exec);
1404
1405void would_dump(struct linux_binprm *bprm, struct file *file)
1406{
1407        struct inode *inode = file_inode(file);
1408        struct user_namespace *mnt_userns = file_mnt_user_ns(file);
1409        if (inode_permission(mnt_userns, inode, MAY_READ) < 0) {
1410                struct user_namespace *old, *user_ns;
1411                bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1412
1413                /* Ensure mm->user_ns contains the executable */
1414                user_ns = old = bprm->mm->user_ns;
1415                while ((user_ns != &init_user_ns) &&
1416                       !privileged_wrt_inode_uidgid(user_ns, mnt_userns, inode))
1417                        user_ns = user_ns->parent;
1418
1419                if (old != user_ns) {
1420                        bprm->mm->user_ns = get_user_ns(user_ns);
1421                        put_user_ns(old);
1422                }
1423        }
1424}
1425EXPORT_SYMBOL(would_dump);
1426
1427void setup_new_exec(struct linux_binprm * bprm)
1428{
1429        /* Setup things that can depend upon the personality */
1430        struct task_struct *me = current;
1431
1432        arch_pick_mmap_layout(me->mm, &bprm->rlim_stack);
1433
1434        arch_setup_new_exec();
1435
1436        /* Set the new mm task size. We have to do that late because it may
1437         * depend on TIF_32BIT which is only updated in flush_thread() on
1438         * some architectures like powerpc
1439         */
1440        me->mm->task_size = TASK_SIZE;
1441        up_write(&me->signal->exec_update_lock);
1442        mutex_unlock(&me->signal->cred_guard_mutex);
1443}
1444EXPORT_SYMBOL(setup_new_exec);
1445
1446/* Runs immediately before start_thread() takes over. */
1447void finalize_exec(struct linux_binprm *bprm)
1448{
1449        /* Store any stack rlimit changes before starting thread. */
1450        task_lock(current->group_leader);
1451        current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
1452        task_unlock(current->group_leader);
1453}
1454EXPORT_SYMBOL(finalize_exec);
1455
1456/*
1457 * Prepare credentials and lock ->cred_guard_mutex.
1458 * setup_new_exec() commits the new creds and drops the lock.
1459 * Or, if exec fails before, free_bprm() should release ->cred
1460 * and unlock.
1461 */
1462static int prepare_bprm_creds(struct linux_binprm *bprm)
1463{
1464        if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1465                return -ERESTARTNOINTR;
1466
1467        bprm->cred = prepare_exec_creds();
1468        if (likely(bprm->cred))
1469                return 0;
1470
1471        mutex_unlock(&current->signal->cred_guard_mutex);
1472        return -ENOMEM;
1473}
1474
1475static void free_bprm(struct linux_binprm *bprm)
1476{
1477        if (bprm->mm) {
1478                acct_arg_size(bprm, 0);
1479                mmput(bprm->mm);
1480        }
1481        free_arg_pages(bprm);
1482        if (bprm->cred) {
1483                mutex_unlock(&current->signal->cred_guard_mutex);
1484                abort_creds(bprm->cred);
1485        }
1486        if (bprm->file) {
1487                allow_write_access(bprm->file);
1488                fput(bprm->file);
1489        }
1490        if (bprm->executable)
1491                fput(bprm->executable);
1492        /* If a binfmt changed the interp, free it. */
1493        if (bprm->interp != bprm->filename)
1494                kfree(bprm->interp);
1495        kfree(bprm->fdpath);
1496        kfree(bprm);
1497}
1498
1499static struct linux_binprm *alloc_bprm(int fd, struct filename *filename)
1500{
1501        struct linux_binprm *bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1502        int retval = -ENOMEM;
1503        if (!bprm)
1504                goto out;
1505
1506        if (fd == AT_FDCWD || filename->name[0] == '/') {
1507                bprm->filename = filename->name;
1508        } else {
1509                if (filename->name[0] == '\0')
1510                        bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
1511                else
1512                        bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
1513                                                  fd, filename->name);
1514                if (!bprm->fdpath)
1515                        goto out_free;
1516
1517                bprm->filename = bprm->fdpath;
1518        }
1519        bprm->interp = bprm->filename;
1520
1521        retval = bprm_mm_init(bprm);
1522        if (retval)
1523                goto out_free;
1524        return bprm;
1525
1526out_free:
1527        free_bprm(bprm);
1528out:
1529        return ERR_PTR(retval);
1530}
1531
1532int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
1533{
1534        /* If a binfmt changed the interp, free it first. */
1535        if (bprm->interp != bprm->filename)
1536                kfree(bprm->interp);
1537        bprm->interp = kstrdup(interp, GFP_KERNEL);
1538        if (!bprm->interp)
1539                return -ENOMEM;
1540        return 0;
1541}
1542EXPORT_SYMBOL(bprm_change_interp);
1543
1544/*
1545 * determine how safe it is to execute the proposed program
1546 * - the caller must hold ->cred_guard_mutex to protect against
1547 *   PTRACE_ATTACH or seccomp thread-sync
1548 */
1549static void check_unsafe_exec(struct linux_binprm *bprm)
1550{
1551        struct task_struct *p = current, *t;
1552        unsigned n_fs;
1553
1554        if (p->ptrace)
1555                bprm->unsafe |= LSM_UNSAFE_PTRACE;
1556
1557        /*
1558         * This isn't strictly necessary, but it makes it harder for LSMs to
1559         * mess up.
1560         */
1561        if (task_no_new_privs(current))
1562                bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1563
1564        t = p;
1565        n_fs = 1;
1566        spin_lock(&p->fs->lock);
1567        rcu_read_lock();
1568        while_each_thread(p, t) {
1569                if (t->fs == p->fs)
1570                        n_fs++;
1571        }
1572        rcu_read_unlock();
1573
1574        if (p->fs->users > n_fs)
1575                bprm->unsafe |= LSM_UNSAFE_SHARE;
1576        else
1577                p->fs->in_exec = 1;
1578        spin_unlock(&p->fs->lock);
1579}
1580
1581static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
1582{
1583        /* Handle suid and sgid on files */
1584        struct user_namespace *mnt_userns;
1585        struct inode *inode;
1586        unsigned int mode;
1587        kuid_t uid;
1588        kgid_t gid;
1589
1590        if (!mnt_may_suid(file->f_path.mnt))
1591                return;
1592
1593        if (task_no_new_privs(current))
1594                return;
1595
1596        inode = file->f_path.dentry->d_inode;
1597        mode = READ_ONCE(inode->i_mode);
1598        if (!(mode & (S_ISUID|S_ISGID)))
1599                return;
1600
1601        mnt_userns = file_mnt_user_ns(file);
1602
1603        /* Be careful if suid/sgid is set */
1604        inode_lock(inode);
1605
1606        /* reload atomically mode/uid/gid now that lock held */
1607        mode = inode->i_mode;
1608        uid = i_uid_into_mnt(mnt_userns, inode);
1609        gid = i_gid_into_mnt(mnt_userns, inode);
1610        inode_unlock(inode);
1611
1612        /* We ignore suid/sgid if there are no mappings for them in the ns */
1613        if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1614                 !kgid_has_mapping(bprm->cred->user_ns, gid))
1615                return;
1616
1617        if (mode & S_ISUID) {
1618                bprm->per_clear |= PER_CLEAR_ON_SETID;
1619                bprm->cred->euid = uid;
1620        }
1621
1622        if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1623                bprm->per_clear |= PER_CLEAR_ON_SETID;
1624                bprm->cred->egid = gid;
1625        }
1626}
1627
1628/*
1629 * Compute brpm->cred based upon the final binary.
1630 */
1631static int bprm_creds_from_file(struct linux_binprm *bprm)
1632{
1633        /* Compute creds based on which file? */
1634        struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file;
1635
1636        bprm_fill_uid(bprm, file);
1637        return security_bprm_creds_from_file(bprm, file);
1638}
1639
1640/*
1641 * Fill the binprm structure from the inode.
1642 * Read the first BINPRM_BUF_SIZE bytes
1643 *
1644 * This may be called multiple times for binary chains (scripts for example).
1645 */
1646static int prepare_binprm(struct linux_binprm *bprm)
1647{
1648        loff_t pos = 0;
1649
1650        memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1651        return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
1652}
1653
1654/*
1655 * Arguments are '\0' separated strings found at the location bprm->p
1656 * points to; chop off the first by relocating brpm->p to right after
1657 * the first '\0' encountered.
1658 */
1659int remove_arg_zero(struct linux_binprm *bprm)
1660{
1661        int ret = 0;
1662        unsigned long offset;
1663        char *kaddr;
1664        struct page *page;
1665
1666        if (!bprm->argc)
1667                return 0;
1668
1669        do {
1670                offset = bprm->p & ~PAGE_MASK;
1671                page = get_arg_page(bprm, bprm->p, 0);
1672                if (!page) {
1673                        ret = -EFAULT;
1674                        goto out;
1675                }
1676                kaddr = kmap_atomic(page);
1677
1678                for (; offset < PAGE_SIZE && kaddr[offset];
1679                                offset++, bprm->p++)
1680                        ;
1681
1682                kunmap_atomic(kaddr);
1683                put_arg_page(page);
1684        } while (offset == PAGE_SIZE);
1685
1686        bprm->p++;
1687        bprm->argc--;
1688        ret = 0;
1689
1690out:
1691        return ret;
1692}
1693EXPORT_SYMBOL(remove_arg_zero);
1694
1695#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1696/*
1697 * cycle the list of binary formats handler, until one recognizes the image
1698 */
1699static int search_binary_handler(struct linux_binprm *bprm)
1700{
1701        bool need_retry = IS_ENABLED(CONFIG_MODULES);
1702        struct linux_binfmt *fmt;
1703        int retval;
1704
1705        retval = prepare_binprm(bprm);
1706        if (retval < 0)
1707                return retval;
1708
1709        retval = security_bprm_check(bprm);
1710        if (retval)
1711                return retval;
1712
1713        retval = -ENOENT;
1714 retry:
1715        read_lock(&binfmt_lock);
1716        list_for_each_entry(fmt, &formats, lh) {
1717                if (!try_module_get(fmt->module))
1718                        continue;
1719                read_unlock(&binfmt_lock);
1720
1721                retval = fmt->load_binary(bprm);
1722
1723                read_lock(&binfmt_lock);
1724                put_binfmt(fmt);
1725                if (bprm->point_of_no_return || (retval != -ENOEXEC)) {
1726                        read_unlock(&binfmt_lock);
1727                        return retval;
1728                }
1729        }
1730        read_unlock(&binfmt_lock);
1731
1732        if (need_retry) {
1733                if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1734                    printable(bprm->buf[2]) && printable(bprm->buf[3]))
1735                        return retval;
1736                if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1737                        return retval;
1738                need_retry = false;
1739                goto retry;
1740        }
1741
1742        return retval;
1743}
1744
1745static int exec_binprm(struct linux_binprm *bprm)
1746{
1747        pid_t old_pid, old_vpid;
1748        int ret, depth;
1749
1750        /* Need to fetch pid before load_binary changes it */
1751        old_pid = current->pid;
1752        rcu_read_lock();
1753        old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1754        rcu_read_unlock();
1755
1756        /* This allows 4 levels of binfmt rewrites before failing hard. */
1757        for (depth = 0;; depth++) {
1758                struct file *exec;
1759                if (depth > 5)
1760                        return -ELOOP;
1761
1762                ret = search_binary_handler(bprm);
1763                if (ret < 0)
1764                        return ret;
1765                if (!bprm->interpreter)
1766                        break;
1767
1768                exec = bprm->file;
1769                bprm->file = bprm->interpreter;
1770                bprm->interpreter = NULL;
1771
1772                allow_write_access(exec);
1773                if (unlikely(bprm->have_execfd)) {
1774                        if (bprm->executable) {
1775                                fput(exec);
1776                                return -ENOEXEC;
1777                        }
1778                        bprm->executable = exec;
1779                } else
1780                        fput(exec);
1781        }
1782
1783        audit_bprm(bprm);
1784        trace_sched_process_exec(current, old_pid, bprm);
1785        ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1786        proc_exec_connector(current);
1787        return 0;
1788}
1789
1790/*
1791 * sys_execve() executes a new program.
1792 */
1793static int bprm_execve(struct linux_binprm *bprm,
1794                       int fd, struct filename *filename, int flags)
1795{
1796        struct file *file;
1797        int retval;
1798
1799        retval = prepare_bprm_creds(bprm);
1800        if (retval)
1801                return retval;
1802
1803        check_unsafe_exec(bprm);
1804        current->in_execve = 1;
1805
1806        file = do_open_execat(fd, filename, flags);
1807        retval = PTR_ERR(file);
1808        if (IS_ERR(file))
1809                goto out_unmark;
1810
1811        sched_exec();
1812
1813        bprm->file = file;
1814        /*
1815         * Record that a name derived from an O_CLOEXEC fd will be
1816         * inaccessible after exec.  This allows the code in exec to
1817         * choose to fail when the executable is not mmaped into the
1818         * interpreter and an open file descriptor is not passed to
1819         * the interpreter.  This makes for a better user experience
1820         * than having the interpreter start and then immediately fail
1821         * when it finds the executable is inaccessible.
1822         */
1823        if (bprm->fdpath && get_close_on_exec(fd))
1824                bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1825
1826        /* Set the unchanging part of bprm->cred */
1827        retval = security_bprm_creds_for_exec(bprm);
1828        if (retval)
1829                goto out;
1830
1831        retval = exec_binprm(bprm);
1832        if (retval < 0)
1833                goto out;
1834
1835        /* execve succeeded */
1836        current->fs->in_exec = 0;
1837        current->in_execve = 0;
1838        rseq_execve(current);
1839        acct_update_integrals(current);
1840        task_numa_free(current, false);
1841        return retval;
1842
1843out:
1844        /*
1845         * If past the point of no return ensure the code never
1846         * returns to the userspace process.  Use an existing fatal
1847         * signal if present otherwise terminate the process with
1848         * SIGSEGV.
1849         */
1850        if (bprm->point_of_no_return && !fatal_signal_pending(current))
1851                force_sigsegv(SIGSEGV);
1852
1853out_unmark:
1854        current->fs->in_exec = 0;
1855        current->in_execve = 0;
1856
1857        return retval;
1858}
1859
1860static int do_execveat_common(int fd, struct filename *filename,
1861                              struct user_arg_ptr argv,
1862                              struct user_arg_ptr envp,
1863                              int flags)
1864{
1865        struct linux_binprm *bprm;
1866        int retval;
1867
1868        if (IS_ERR(filename))
1869                return PTR_ERR(filename);
1870
1871        /*
1872         * We move the actual failure in case of RLIMIT_NPROC excess from
1873         * set*uid() to execve() because too many poorly written programs
1874         * don't check setuid() return code.  Here we additionally recheck
1875         * whether NPROC limit is still exceeded.
1876         */
1877        if ((current->flags & PF_NPROC_EXCEEDED) &&
1878            is_ucounts_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
1879                retval = -EAGAIN;
1880                goto out_ret;
1881        }
1882
1883        /* We're below the limit (still or again), so we don't want to make
1884         * further execve() calls fail. */
1885        current->flags &= ~PF_NPROC_EXCEEDED;
1886
1887        bprm = alloc_bprm(fd, filename);
1888        if (IS_ERR(bprm)) {
1889                retval = PTR_ERR(bprm);
1890                goto out_ret;
1891        }
1892
1893        retval = count(argv, MAX_ARG_STRINGS);
1894        if (retval < 0)
1895                goto out_free;
1896        bprm->argc = retval;
1897
1898        retval = count(envp, MAX_ARG_STRINGS);
1899        if (retval < 0)
1900                goto out_free;
1901        bprm->envc = retval;
1902
1903        retval = bprm_stack_limits(bprm);
1904        if (retval < 0)
1905                goto out_free;
1906
1907        retval = copy_string_kernel(bprm->filename, bprm);
1908        if (retval < 0)
1909                goto out_free;
1910        bprm->exec = bprm->p;
1911
1912        retval = copy_strings(bprm->envc, envp, bprm);
1913        if (retval < 0)
1914                goto out_free;
1915
1916        retval = copy_strings(bprm->argc, argv, bprm);
1917        if (retval < 0)
1918                goto out_free;
1919
1920        retval = bprm_execve(bprm, fd, filename, flags);
1921out_free:
1922        free_bprm(bprm);
1923
1924out_ret:
1925        putname(filename);
1926        return retval;
1927}
1928
1929int kernel_execve(const char *kernel_filename,
1930                  const char *const *argv, const char *const *envp)
1931{
1932        struct filename *filename;
1933        struct linux_binprm *bprm;
1934        int fd = AT_FDCWD;
1935        int retval;
1936
1937        filename = getname_kernel(kernel_filename);
1938        if (IS_ERR(filename))
1939                return PTR_ERR(filename);
1940
1941        bprm = alloc_bprm(fd, filename);
1942        if (IS_ERR(bprm)) {
1943                retval = PTR_ERR(bprm);
1944                goto out_ret;
1945        }
1946
1947        retval = count_strings_kernel(argv);
1948        if (retval < 0)
1949                goto out_free;
1950        bprm->argc = retval;
1951
1952        retval = count_strings_kernel(envp);
1953        if (retval < 0)
1954                goto out_free;
1955        bprm->envc = retval;
1956
1957        retval = bprm_stack_limits(bprm);
1958        if (retval < 0)
1959                goto out_free;
1960
1961        retval = copy_string_kernel(bprm->filename, bprm);
1962        if (retval < 0)
1963                goto out_free;
1964        bprm->exec = bprm->p;
1965
1966        retval = copy_strings_kernel(bprm->envc, envp, bprm);
1967        if (retval < 0)
1968                goto out_free;
1969
1970        retval = copy_strings_kernel(bprm->argc, argv, bprm);
1971        if (retval < 0)
1972                goto out_free;
1973
1974        retval = bprm_execve(bprm, fd, filename, 0);
1975out_free:
1976        free_bprm(bprm);
1977out_ret:
1978        putname(filename);
1979        return retval;
1980}
1981
1982static int do_execve(struct filename *filename,
1983        const char __user *const __user *__argv,
1984        const char __user *const __user *__envp)
1985{
1986        struct user_arg_ptr argv = { .ptr.native = __argv };
1987        struct user_arg_ptr envp = { .ptr.native = __envp };
1988        return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1989}
1990
1991static int do_execveat(int fd, struct filename *filename,
1992                const char __user *const __user *__argv,
1993                const char __user *const __user *__envp,
1994                int flags)
1995{
1996        struct user_arg_ptr argv = { .ptr.native = __argv };
1997        struct user_arg_ptr envp = { .ptr.native = __envp };
1998
1999        return do_execveat_common(fd, filename, argv, envp, flags);
2000}
2001
2002#ifdef CONFIG_COMPAT
2003static int compat_do_execve(struct filename *filename,
2004        const compat_uptr_t __user *__argv,
2005        const compat_uptr_t __user *__envp)
2006{
2007        struct user_arg_ptr argv = {
2008                .is_compat = true,
2009                .ptr.compat = __argv,
2010        };
2011        struct user_arg_ptr envp = {
2012                .is_compat = true,
2013                .ptr.compat = __envp,
2014        };
2015        return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
2016}
2017
2018static int compat_do_execveat(int fd, struct filename *filename,
2019                              const compat_uptr_t __user *__argv,
2020                              const compat_uptr_t __user *__envp,
2021                              int flags)
2022{
2023        struct user_arg_ptr argv = {
2024                .is_compat = true,
2025                .ptr.compat = __argv,
2026        };
2027        struct user_arg_ptr envp = {
2028                .is_compat = true,
2029                .ptr.compat = __envp,
2030        };
2031        return do_execveat_common(fd, filename, argv, envp, flags);
2032}
2033#endif
2034
2035void set_binfmt(struct linux_binfmt *new)
2036{
2037        struct mm_struct *mm = current->mm;
2038
2039        if (mm->binfmt)
2040                module_put(mm->binfmt->module);
2041
2042        mm->binfmt = new;
2043        if (new)
2044                __module_get(new->module);
2045}
2046EXPORT_SYMBOL(set_binfmt);
2047
2048/*
2049 * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
2050 */
2051void set_dumpable(struct mm_struct *mm, int value)
2052{
2053        if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
2054                return;
2055
2056        set_mask_bits(&mm->flags, MMF_DUMPABLE_MASK, value);
2057}
2058
2059SYSCALL_DEFINE3(execve,
2060                const char __user *, filename,
2061                const char __user *const __user *, argv,
2062                const char __user *const __user *, envp)
2063{
2064        return do_execve(getname(filename), argv, envp);
2065}
2066
2067SYSCALL_DEFINE5(execveat,
2068                int, fd, const char __user *, filename,
2069                const char __user *const __user *, argv,
2070                const char __user *const __user *, envp,
2071                int, flags)
2072{
2073        int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
2074
2075        return do_execveat(fd,
2076                           getname_flags(filename, lookup_flags, NULL),
2077                           argv, envp, flags);
2078}
2079
2080#ifdef CONFIG_COMPAT
2081COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
2082        const compat_uptr_t __user *, argv,
2083        const compat_uptr_t __user *, envp)
2084{
2085        return compat_do_execve(getname(filename), argv, envp);
2086}
2087
2088COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
2089                       const char __user *, filename,
2090                       const compat_uptr_t __user *, argv,
2091                       const compat_uptr_t __user *, envp,
2092                       int,  flags)
2093{
2094        int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
2095
2096        return compat_do_execveat(fd,
2097                                  getname_flags(filename, lookup_flags, NULL),
2098                                  argv, envp, flags);
2099}
2100#endif
2101
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