fs/exec.c

   1 /*
   2  *  linux/fs/exec.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  * #!-checking implemented by tytso.
   9  */
  10 /*
  11  * Demand-loading implemented 01.12.91 - no need to read anything but
  12  * the header into memory. The inode of the executable is put into
  13  * "current->executable", and page faults do the actual loading. Clean.
  14  *
  15  * Once more I can proudly say that linux stood up to being changed: it
  16  * was less than 2 hours work to get demand-loading completely implemented.
  17  *
  18  * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
  19  * current->executable is only used by the procfs.  This allows a dispatch
  20  * table to check for several different types  of binary formats.  We keep
  21  * trying until we recognize the file or we run out of supported binary
  22  * formats.
  23  */
  24
  25 #include <linux/slab.h>
  26 #include <linux/file.h>
  27 #include <linux/fdtable.h>
  28 #include <linux/mm.h>
  29 #include <linux/vmacache.h>
  30 #include <linux/stat.h>
  31 #include <linux/fcntl.h>
  32 #include <linux/swap.h>
  33 #include <linux/string.h>
  34 #include <linux/init.h>
  35 #include <linux/pagemap.h>
  36 #include <linux/perf_event.h>
  37 #include <linux/highmem.h>
  38 #include <linux/spinlock.h>
  39 #include <linux/key.h>
  40 #include <linux/personality.h>
  41 #include <linux/binfmts.h>
  42 #include <linux/utsname.h>
  43 #include <linux/pid_namespace.h>
  44 #include <linux/module.h>
  45 #include <linux/namei.h>
  46 #include <linux/mount.h>
  47 #include <linux/security.h>
  48 #include <linux/syscalls.h>
  49 #include <linux/tsacct_kern.h>
  50 #include <linux/cn_proc.h>
  51 #include <linux/audit.h>
  52 #include <linux/tracehook.h>
  53 #include <linux/kmod.h>
  54 #include <linux/fsnotify.h>
  55 #include <linux/fs_struct.h>
  56 #include <linux/pipe_fs_i.h>
  57 #include <linux/oom.h>
  58 #include <linux/compat.h>
  59 #include <linux/user_namespace.h>
  60
  61 #include <asm/uaccess.h>
  62 #include <asm/mmu_context.h>
  63 #include <asm/tlb.h>
  64
  65 #include <trace/events/task.h>
  66 #include "internal.h"
  67
  68 #include <trace/events/sched.h>
  69
  70 int suid_dumpable = 0;
  71
  72 static LIST_HEAD(formats);
  73 static DEFINE_RWLOCK(binfmt_lock);
  74
  75 void __register_binfmt(struct linux_binfmt * fmt, int insert)
  76 {
  77         BUG_ON(!fmt);
  78         if (WARN_ON(!fmt->load_binary))
  79                 return;
  80         write_lock(&binfmt_lock);
  81         insert ? list_add(&fmt->lh, &formats) :
  82                  list_add_tail(&fmt->lh, &formats);
  83         write_unlock(&binfmt_lock);
  84 }
  85
  86 EXPORT_SYMBOL(__register_binfmt);
  87
  88 void unregister_binfmt(struct linux_binfmt * fmt)
  89 {
  90         write_lock(&binfmt_lock);
  91         list_del(&fmt->lh);
  92         write_unlock(&binfmt_lock);
  93 }
  94
  95 EXPORT_SYMBOL(unregister_binfmt);
  96
  97 static inline void put_binfmt(struct linux_binfmt * fmt)
  98 {
  99         module_put(fmt->module);
 100 }
 101
 102 bool path_noexec(const struct path *path)
 103 {
 104         return (path->mnt->mnt_flags & MNT_NOEXEC) ||
 105                (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
 106 }
 107
 108 #ifdef CONFIG_USELIB
 109 /*
 110  * Note that a shared library must be both readable and executable due to
 111  * security reasons.
 112  *
 113  * Also note that we take the address to load from from the file itself.
 114  */
 115 SYSCALL_DEFINE1(uselib, const char __user *, library)
 116 {
 117         struct linux_binfmt *fmt;
 118         struct file *file;
 119         struct filename *tmp = getname(library);
 120         int error = PTR_ERR(tmp);
 121         static const struct open_flags uselib_flags = {
 122                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 123                 .acc_mode = MAY_READ | MAY_EXEC | MAY_OPEN,
 124                 .intent = LOOKUP_OPEN,
 125                 .lookup_flags = LOOKUP_FOLLOW,
 126         };
 127
 128         if (IS_ERR(tmp))
 129                 goto out;
 130
 131         file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
 132         putname(tmp);
 133         error = PTR_ERR(file);
 134         if (IS_ERR(file))
 135                 goto out;
 136
 137         error = -EINVAL;
 138         if (!S_ISREG(file_inode(file)->i_mode))
 139                 goto exit;
 140
 141         error = -EACCES;
 142         if (path_noexec(&file->f_path))
 143                 goto exit;
 144
 145         fsnotify_open(file);
 146
 147         error = -ENOEXEC;
 148
 149         read_lock(&binfmt_lock);
 150         list_for_each_entry(fmt, &formats, lh) {
 151                 if (!fmt->load_shlib)
 152                         continue;
 153                 if (!try_module_get(fmt->module))
 154                         continue;
 155                 read_unlock(&binfmt_lock);
 156                 error = fmt->load_shlib(file);
 157                 read_lock(&binfmt_lock);
 158                 put_binfmt(fmt);
 159                 if (error != -ENOEXEC)
 160                         break;
 161         }
 162         read_unlock(&binfmt_lock);
 163 exit:
 164         fput(file);
 165 out:
 166         return error;
 167 }
 168 #endif /* #ifdef CONFIG_USELIB */
 169
 170 #ifdef CONFIG_MMU
 171 /*
 172  * The nascent bprm->mm is not visible until exec_mmap() but it can
 173  * use a lot of memory, account these pages in current->mm temporary
 174  * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
 175  * change the counter back via acct_arg_size(0).
 176  */
 177 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 178 {
 179         struct mm_struct *mm = current->mm;
 180         long diff = (long)(pages - bprm->vma_pages);
 181
 182         if (!mm || !diff)
 183                 return;
 184
 185         bprm->vma_pages = pages;
 186         add_mm_counter(mm, MM_ANONPAGES, diff);
 187 }
 188
 189 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 190                 int write)
 191 {
 192         struct page *page;
 193         int ret;
 194
 195 #ifdef CONFIG_STACK_GROWSUP
 196         if (write) {
 197                 ret = expand_downwards(bprm->vma, pos);
 198                 if (ret < 0)
 199                         return NULL;
 200         }
 201 #endif
 202         ret = get_user_pages(current, bprm->mm, pos,
 203                         1, write, 1, &page, NULL);
 204         if (ret <= 0)
 205                 return NULL;
 206
 207         if (write) {
 208                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 209                 struct rlimit *rlim;
 210
 211                 acct_arg_size(bprm, size / PAGE_SIZE);
 212
 213                 /*
 214                  * We've historically supported up to 32 pages (ARG_MAX)
 215                  * of argument strings even with small stacks
 216                  */
 217                 if (size <= ARG_MAX)
 218                         return page;
 219
 220                 /*
 221                  * Limit to 1/4-th the stack size for the argv+env strings.
 222                  * This ensures that:
 223                  *  - the remaining binfmt code will not run out of stack space,
 224                  *  - the program will have a reasonable amount of stack left
 225                  *    to work from.
 226                  */
 227                 rlim = current->signal->rlim;
 228                 if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
 229                         put_page(page);
 230                         return NULL;
 231                 }
 232         }
 233
 234         return page;
 235 }
 236
 237 static void put_arg_page(struct page *page)
 238 {
 239         put_page(page);
 240 }
 241
 242 static void free_arg_page(struct linux_binprm *bprm, int i)
 243 {
 244 }
 245
 246 static void free_arg_pages(struct linux_binprm *bprm)
 247 {
 248 }
 249
 250 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 251                 struct page *page)
 252 {
 253         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 254 }
 255
 256 static int __bprm_mm_init(struct linux_binprm *bprm)
 257 {
 258         int err;
 259         struct vm_area_struct *vma = NULL;
 260         struct mm_struct *mm = bprm->mm;
 261
 262         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 263         if (!vma)
 264                 return -ENOMEM;
 265
 266         down_write(&mm->mmap_sem);
 267         vma->vm_mm = mm;
 268
 269         /*
 270          * Place the stack at the largest stack address the architecture
 271          * supports. Later, we'll move this to an appropriate place. We don't
 272          * use STACK_TOP because that can depend on attributes which aren't
 273          * configured yet.
 274          */
 275         BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 276         vma->vm_end = STACK_TOP_MAX;
 277         vma->vm_start = vma->vm_end - PAGE_SIZE;
 278         vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 279         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 280         INIT_LIST_HEAD(&vma->anon_vma_chain);
 281
 282         err = insert_vm_struct(mm, vma);
 283         if (err)
 284                 goto err;
 285
 286         mm->stack_vm = mm->total_vm = 1;
 287         arch_bprm_mm_init(mm, vma);
 288         up_write(&mm->mmap_sem);
 289         bprm->p = vma->vm_end - sizeof(void *);
 290         return 0;
 291 err:
 292         up_write(&mm->mmap_sem);
 293         bprm->vma = NULL;
 294         kmem_cache_free(vm_area_cachep, vma);
 295         return err;
 296 }
 297
 298 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 299 {
 300         return len <= MAX_ARG_STRLEN;
 301 }
 302
 303 #else
 304
 305 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 306 {
 307 }
 308
 309 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 310                 int write)
 311 {
 312         struct page *page;
 313
 314         page = bprm->page[pos / PAGE_SIZE];
 315         if (!page && write) {
 316                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 317                 if (!page)
 318                         return NULL;
 319                 bprm->page[pos / PAGE_SIZE] = page;
 320         }
 321
 322         return page;
 323 }
 324
 325 static void put_arg_page(struct page *page)
 326 {
 327 }
 328
 329 static void free_arg_page(struct linux_binprm *bprm, int i)
 330 {
 331         if (bprm->page[i]) {
 332                 __free_page(bprm->page[i]);
 333                 bprm->page[i] = NULL;
 334         }
 335 }
 336
 337 static void free_arg_pages(struct linux_binprm *bprm)
 338 {
 339         int i;
 340
 341         for (i = 0; i < MAX_ARG_PAGES; i++)
 342                 free_arg_page(bprm, i);
 343 }
 344
 345 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 346                 struct page *page)
 347 {
 348 }
 349
 350 static int __bprm_mm_init(struct linux_binprm *bprm)
 351 {
 352         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 353         return 0;
 354 }
 355
 356 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 357 {
 358         return len <= bprm->p;
 359 }
 360
 361 #endif /* CONFIG_MMU */
 362
 363 /*
 364  * Create a new mm_struct and populate it with a temporary stack
 365  * vm_area_struct.  We don't have enough context at this point to set the stack
 366  * flags, permissions, and offset, so we use temporary values.  We'll update
 367  * them later in setup_arg_pages().
 368  */
 369 static int bprm_mm_init(struct linux_binprm *bprm)
 370 {
 371         int err;
 372         struct mm_struct *mm = NULL;
 373
 374         bprm->mm = mm = mm_alloc();
 375         err = -ENOMEM;
 376         if (!mm)
 377                 goto err;
 378
 379         err = __bprm_mm_init(bprm);
 380         if (err)
 381                 goto err;
 382
 383         return 0;
 384
 385 err:
 386         if (mm) {
 387                 bprm->mm = NULL;
 388                 mmdrop(mm);
 389         }
 390
 391         return err;
 392 }
 393
 394 struct user_arg_ptr {
 395 #ifdef CONFIG_COMPAT
 396         bool is_compat;
 397 #endif
 398         union {
 399                 const char __user *const __user *native;
 400 #ifdef CONFIG_COMPAT
 401                 const compat_uptr_t __user *compat;
 402 #endif
 403         } ptr;
 404 };
 405
 406 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
 407 {
 408         const char __user *native;
 409
 410 #ifdef CONFIG_COMPAT
 411         if (unlikely(argv.is_compat)) {
 412                 compat_uptr_t compat;
 413
 414                 if (get_user(compat, argv.ptr.compat + nr))
 415                         return ERR_PTR(-EFAULT);
 416
 417                 return compat_ptr(compat);
 418         }
 419 #endif
 420
 421         if (get_user(native, argv.ptr.native + nr))
 422                 return ERR_PTR(-EFAULT);
 423
 424         return native;
 425 }
 426
 427 /*
 428  * count() counts the number of strings in array ARGV.
 429  */
 430 static int count(struct user_arg_ptr argv, int max)
 431 {
 432         int i = 0;
 433
 434         if (argv.ptr.native != NULL) {
 435                 for (;;) {
 436                         const char __user *p = get_user_arg_ptr(argv, i);
 437
 438                         if (!p)
 439                                 break;
 440
 441                         if (IS_ERR(p))
 442                                 return -EFAULT;
 443
 444                         if (i >= max)
 445                                 return -E2BIG;
 446                         ++i;
 447
 448                         if (fatal_signal_pending(current))
 449                                 return -ERESTARTNOHAND;
 450                         cond_resched();
 451                 }
 452         }
 453         return i;
 454 }
 455
 456 /*
 457  * 'copy_strings()' copies argument/environment strings from the old
 458  * processes's memory to the new process's stack.  The call to get_user_pages()
 459  * ensures the destination page is created and not swapped out.
 460  */
 461 static int copy_strings(int argc, struct user_arg_ptr argv,
 462                         struct linux_binprm *bprm)
 463 {
 464         struct page *kmapped_page = NULL;
 465         char *kaddr = NULL;
 466         unsigned long kpos = 0;
 467         int ret;
 468
 469         while (argc-- > 0) {
 470                 const char __user *str;
 471                 int len;
 472                 unsigned long pos;
 473
 474                 ret = -EFAULT;
 475                 str = get_user_arg_ptr(argv, argc);
 476                 if (IS_ERR(str))
 477                         goto out;
 478
 479                 len = strnlen_user(str, MAX_ARG_STRLEN);
 480                 if (!len)
 481                         goto out;
 482
 483                 ret = -E2BIG;
 484                 if (!valid_arg_len(bprm, len))
 485                         goto out;
 486
 487                 /* We're going to work our way backwords. */
 488                 pos = bprm->p;
 489                 str += len;
 490                 bprm->p -= len;
 491
 492                 while (len > 0) {
 493                         int offset, bytes_to_copy;
 494
 495                         if (fatal_signal_pending(current)) {
 496                                 ret = -ERESTARTNOHAND;
 497                                 goto out;
 498                         }
 499                         cond_resched();
 500
 501                         offset = pos % PAGE_SIZE;
 502                         if (offset == 0)
 503                                 offset = PAGE_SIZE;
 504
 505                         bytes_to_copy = offset;
 506                         if (bytes_to_copy > len)
 507                                 bytes_to_copy = len;
 508
 509                         offset -= bytes_to_copy;
 510                         pos -= bytes_to_copy;
 511                         str -= bytes_to_copy;
 512                         len -= bytes_to_copy;
 513
 514                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 515                                 struct page *page;
 516
 517                                 page = get_arg_page(bprm, pos, 1);
 518                                 if (!page) {
 519                                         ret = -E2BIG;
 520                                         goto out;
 521                                 }
 522
 523                                 if (kmapped_page) {
 524                                         flush_kernel_dcache_page(kmapped_page);
 525                                         kunmap(kmapped_page);
 526                                         put_arg_page(kmapped_page);
 527                                 }
 528                                 kmapped_page = page;
 529                                 kaddr = kmap(kmapped_page);
 530                                 kpos = pos & PAGE_MASK;
 531                                 flush_arg_page(bprm, kpos, kmapped_page);
 532                         }
 533                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 534                                 ret = -EFAULT;
 535                                 goto out;
 536                         }
 537                 }
 538         }
 539         ret = 0;
 540 out:
 541         if (kmapped_page) {
 542                 flush_kernel_dcache_page(kmapped_page);
 543                 kunmap(kmapped_page);
 544                 put_arg_page(kmapped_page);
 545         }
 546         return ret;
 547 }
 548
 549 /*
 550  * Like copy_strings, but get argv and its values from kernel memory.
 551  */
 552 int copy_strings_kernel(int argc, const char *const *__argv,
 553                         struct linux_binprm *bprm)
 554 {
 555         int r;
 556         mm_segment_t oldfs = get_fs();
 557         struct user_arg_ptr argv = {
 558                 .ptr.native = (const char __user *const  __user *)__argv,
 559         };
 560
 561         set_fs(KERNEL_DS);
 562         r = copy_strings(argc, argv, bprm);
 563         set_fs(oldfs);
 564
 565         return r;
 566 }
 567 EXPORT_SYMBOL(copy_strings_kernel);
 568
 569 #ifdef CONFIG_MMU
 570
 571 /*
 572  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 573  * the binfmt code determines where the new stack should reside, we shift it to
 574  * its final location.  The process proceeds as follows:
 575  *
 576  * 1) Use shift to calculate the new vma endpoints.
 577  * 2) Extend vma to cover both the old and new ranges.  This ensures the
 578  *    arguments passed to subsequent functions are consistent.
 579  * 3) Move vma's page tables to the new range.
 580  * 4) Free up any cleared pgd range.
 581  * 5) Shrink the vma to cover only the new range.
 582  */
 583 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 584 {
 585         struct mm_struct *mm = vma->vm_mm;
 586         unsigned long old_start = vma->vm_start;
 587         unsigned long old_end = vma->vm_end;
 588         unsigned long length = old_end - old_start;
 589         unsigned long new_start = old_start - shift;
 590         unsigned long new_end = old_end - shift;
 591         struct mmu_gather tlb;
 592
 593         BUG_ON(new_start > new_end);
 594
 595         /*
 596          * ensure there are no vmas between where we want to go
 597          * and where we are
 598          */
 599         if (vma != find_vma(mm, new_start))
 600                 return -EFAULT;
 601
 602         /*
 603          * cover the whole range: [new_start, old_end)
 604          */
 605         if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
 606                 return -ENOMEM;
 607
 608         /*
 609          * move the page tables downwards, on failure we rely on
 610          * process cleanup to remove whatever mess we made.
 611          */
 612         if (length != move_page_tables(vma, old_start,
 613                                        vma, new_start, length, false))
 614                 return -ENOMEM;
 615
 616         lru_add_drain();
 617         tlb_gather_mmu(&tlb, mm, old_start, old_end);
 618         if (new_end > old_start) {
 619                 /*
 620                  * when the old and new regions overlap clear from new_end.
 621                  */
 622                 free_pgd_range(&tlb, new_end, old_end, new_end,
 623                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 624         } else {
 625                 /*
 626                  * otherwise, clean from old_start; this is done to not touch
 627                  * the address space in [new_end, old_start) some architectures
 628                  * have constraints on va-space that make this illegal (IA64) -
 629                  * for the others its just a little faster.
 630                  */
 631                 free_pgd_range(&tlb, old_start, old_end, new_end,
 632                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 633         }
 634         tlb_finish_mmu(&tlb, old_start, old_end);
 635
 636         /*
 637          * Shrink the vma to just the new range.  Always succeeds.
 638          */
 639         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 640
 641         return 0;
 642 }
 643
 644 /*
 645  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 646  * the stack is optionally relocated, and some extra space is added.
 647  */
 648 int setup_arg_pages(struct linux_binprm *bprm,
 649                     unsigned long stack_top,
 650                     int executable_stack)
 651 {
 652         unsigned long ret;
 653         unsigned long stack_shift;
 654         struct mm_struct *mm = current->mm;
 655         struct vm_area_struct *vma = bprm->vma;
 656         struct vm_area_struct *prev = NULL;
 657         unsigned long vm_flags;
 658         unsigned long stack_base;
 659         unsigned long stack_size;
 660         unsigned long stack_expand;
 661         unsigned long rlim_stack;
 662
 663 #ifdef CONFIG_STACK_GROWSUP
 664         /* Limit stack size */
 665         stack_base = rlimit_max(RLIMIT_STACK);
 666         if (stack_base > STACK_SIZE_MAX)
 667                 stack_base = STACK_SIZE_MAX;
 668
 669         /* Add space for stack randomization. */
 670         stack_base += (STACK_RND_MASK << PAGE_SHIFT);
 671
 672         /* Make sure we didn't let the argument array grow too large. */
 673         if (vma->vm_end - vma->vm_start > stack_base)
 674                 return -ENOMEM;
 675
 676         stack_base = PAGE_ALIGN(stack_top - stack_base);
 677
 678         stack_shift = vma->vm_start - stack_base;
 679         mm->arg_start = bprm->p - stack_shift;
 680         bprm->p = vma->vm_end - stack_shift;
 681 #else
 682         stack_top = arch_align_stack(stack_top);
 683         stack_top = PAGE_ALIGN(stack_top);
 684
 685         if (unlikely(stack_top < mmap_min_addr) ||
 686             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 687                 return -ENOMEM;
 688
 689         stack_shift = vma->vm_end - stack_top;
 690
 691         bprm->p -= stack_shift;
 692         mm->arg_start = bprm->p;
 693 #endif
 694
 695         if (bprm->loader)
 696                 bprm->loader -= stack_shift;
 697         bprm->exec -= stack_shift;
 698
 699         down_write(&mm->mmap_sem);
 700         vm_flags = VM_STACK_FLAGS;
 701
 702         /*
 703          * Adjust stack execute permissions; explicitly enable for
 704          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 705          * (arch default) otherwise.
 706          */
 707         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 708                 vm_flags |= VM_EXEC;
 709         else if (executable_stack == EXSTACK_DISABLE_X)
 710                 vm_flags &= ~VM_EXEC;
 711         vm_flags |= mm->def_flags;
 712         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 713
 714         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 715                         vm_flags);
 716         if (ret)
 717                 goto out_unlock;
 718         BUG_ON(prev != vma);
 719
 720         /* Move stack pages down in memory. */
 721         if (stack_shift) {
 722                 ret = shift_arg_pages(vma, stack_shift);
 723                 if (ret)
 724                         goto out_unlock;
 725         }
 726
 727         /* mprotect_fixup is overkill to remove the temporary stack flags */
 728         vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
 729
 730         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
 731         stack_size = vma->vm_end - vma->vm_start;
 732         /*
 733          * Align this down to a page boundary as expand_stack
 734          * will align it up.
 735          */
 736         rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 737 #ifdef CONFIG_STACK_GROWSUP
 738         if (stack_size + stack_expand > rlim_stack)
 739                 stack_base = vma->vm_start + rlim_stack;
 740         else
 741                 stack_base = vma->vm_end + stack_expand;
 742 #else
 743         if (stack_size + stack_expand > rlim_stack)
 744                 stack_base = vma->vm_end - rlim_stack;
 745         else
 746                 stack_base = vma->vm_start - stack_expand;
 747 #endif
 748         current->mm->start_stack = bprm->p;
 749         ret = expand_stack(vma, stack_base);
 750         if (ret)
 751                 ret = -EFAULT;
 752
 753 out_unlock:
 754         up_write(&mm->mmap_sem);
 755         return ret;
 756 }
 757 EXPORT_SYMBOL(setup_arg_pages);
 758
 759 #endif /* CONFIG_MMU */
 760
 761 static struct file *do_open_execat(int fd, struct filename *name, int flags)
 762 {
 763         struct file *file;
 764         int err;
 765         struct open_flags open_exec_flags = {
 766                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 767                 .acc_mode = MAY_EXEC | MAY_OPEN,
 768                 .intent = LOOKUP_OPEN,
 769                 .lookup_flags = LOOKUP_FOLLOW,
 770         };
 771
 772         if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 773                 return ERR_PTR(-EINVAL);
 774         if (flags & AT_SYMLINK_NOFOLLOW)
 775                 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
 776         if (flags & AT_EMPTY_PATH)
 777                 open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
 778
 779         file = do_filp_open(fd, name, &open_exec_flags);
 780         if (IS_ERR(file))
 781                 goto out;
 782
 783         err = -EACCES;
 784         if (!S_ISREG(file_inode(file)->i_mode))
 785                 goto exit;
 786
 787         if (path_noexec(&file->f_path))
 788                 goto exit;
 789
 790         err = deny_write_access(file);
 791         if (err)
 792                 goto exit;
 793
 794         if (name->name[0] != '\0')
 795                 fsnotify_open(file);
 796
 797 out:
 798         return file;
 799
 800 exit:
 801         fput(file);
 802         return ERR_PTR(err);
 803 }
 804
 805 struct file *open_exec(const char *name)
 806 {
 807         struct filename *filename = getname_kernel(name);
 808         struct file *f = ERR_CAST(filename);
 809
 810         if (!IS_ERR(filename)) {
 811                 f = do_open_execat(AT_FDCWD, filename, 0);
 812                 putname(filename);
 813         }
 814         return f;
 815 }
 816 EXPORT_SYMBOL(open_exec);
 817
 818 int kernel_read(struct file *file, loff_t offset,
 819                 char *addr, unsigned long count)
 820 {
 821         mm_segment_t old_fs;
 822         loff_t pos = offset;
 823         int result;
 824
 825         old_fs = get_fs();
 826         set_fs(get_ds());
 827         /* The cast to a user pointer is valid due to the set_fs() */
 828         result = vfs_read(file, (void __user *)addr, count, &pos);
 829         set_fs(old_fs);
 830         return result;
 831 }
 832
 833 EXPORT_SYMBOL(kernel_read);
 834
 835 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
 836 {
 837         ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
 838         if (res > 0)
 839                 flush_icache_range(addr, addr + len);
 840         return res;
 841 }
 842 EXPORT_SYMBOL(read_code);
 843
 844 static int exec_mmap(struct mm_struct *mm)
 845 {
 846         struct task_struct *tsk;
 847         struct mm_struct *old_mm, *active_mm;
 848
 849         /* Notify parent that we're no longer interested in the old VM */
 850         tsk = current;
 851         old_mm = current->mm;
 852         mm_release(tsk, old_mm);
 853
 854         if (old_mm) {
 855                 sync_mm_rss(old_mm);
 856                 /*
 857                  * Make sure that if there is a core dump in progress
 858                  * for the old mm, we get out and die instead of going
 859                  * through with the exec.  We must hold mmap_sem around
 860                  * checking core_state and changing tsk->mm.
 861                  */
 862                 down_read(&old_mm->mmap_sem);
 863                 if (unlikely(old_mm->core_state)) {
 864                         up_read(&old_mm->mmap_sem);
 865                         return -EINTR;
 866                 }
 867         }
 868         task_lock(tsk);
 869         active_mm = tsk->active_mm;
 870         tsk->mm = mm;
 871         tsk->active_mm = mm;
 872         activate_mm(active_mm, mm);
 873         tsk->mm->vmacache_seqnum = 0;
 874         vmacache_flush(tsk);
 875         task_unlock(tsk);
 876         if (old_mm) {
 877                 up_read(&old_mm->mmap_sem);
 878                 BUG_ON(active_mm != old_mm);
 879                 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
 880                 mm_update_next_owner(old_mm);
 881                 mmput(old_mm);
 882                 return 0;
 883         }
 884         mmdrop(active_mm);
 885         return 0;
 886 }
 887
 888 /*
 889  * This function makes sure the current process has its own signal table,
 890  * so that flush_signal_handlers can later reset the handlers without
 891  * disturbing other processes.  (Other processes might share the signal
 892  * table via the CLONE_SIGHAND option to clone().)
 893  */
 894 static int de_thread(struct task_struct *tsk)
 895 {
 896         struct signal_struct *sig = tsk->signal;
 897         struct sighand_struct *oldsighand = tsk->sighand;
 898         spinlock_t *lock = &oldsighand->siglock;
 899
 900         if (thread_group_empty(tsk))
 901                 goto no_thread_group;
 902
 903         /*
 904          * Kill all other threads in the thread group.
 905          */
 906         spin_lock_irq(lock);
 907         if (signal_group_exit(sig)) {
 908                 /*
 909                  * Another group action in progress, just
 910                  * return so that the signal is processed.
 911                  */
 912                 spin_unlock_irq(lock);
 913                 return -EAGAIN;
 914         }
 915
 916         sig->group_exit_task = tsk;
 917         sig->notify_count = zap_other_threads(tsk);
 918         if (!thread_group_leader(tsk))
 919                 sig->notify_count--;
 920
 921         while (sig->notify_count) {
 922                 __set_current_state(TASK_KILLABLE);
 923                 spin_unlock_irq(lock);
 924                 schedule();
 925                 if (unlikely(__fatal_signal_pending(tsk)))
 926                         goto killed;
 927                 spin_lock_irq(lock);
 928         }
 929         spin_unlock_irq(lock);
 930
 931         /*
 932          * At this point all other threads have exited, all we have to
 933          * do is to wait for the thread group leader to become inactive,
 934          * and to assume its PID:
 935          */
 936         if (!thread_group_leader(tsk)) {
 937                 struct task_struct *leader = tsk->group_leader;
 938
 939                 for (;;) {
 940                         threadgroup_change_begin(tsk);
 941                         write_lock_irq(&tasklist_lock);
 942                         /*
 943                          * Do this under tasklist_lock to ensure that
 944                          * exit_notify() can't miss ->group_exit_task
 945                          */
 946                         sig->notify_count = -1;
 947                         if (likely(leader->exit_state))
 948                                 break;
 949                         __set_current_state(TASK_KILLABLE);
 950                         write_unlock_irq(&tasklist_lock);
 951                         threadgroup_change_end(tsk);
 952                         schedule();
 953                         if (unlikely(__fatal_signal_pending(tsk)))
 954                                 goto killed;
 955                 }
 956
 957                 /*
 958                  * The only record we have of the real-time age of a
 959                  * process, regardless of execs it's done, is start_time.
 960                  * All the past CPU time is accumulated in signal_struct
 961                  * from sister threads now dead.  But in this non-leader
 962                  * exec, nothing survives from the original leader thread,
 963                  * whose birth marks the true age of this process now.
 964                  * When we take on its identity by switching to its PID, we
 965                  * also take its birthdate (always earlier than our own).
 966                  */
 967                 tsk->start_time = leader->start_time;
 968                 tsk->real_start_time = leader->real_start_time;
 969
 970                 BUG_ON(!same_thread_group(leader, tsk));
 971                 BUG_ON(has_group_leader_pid(tsk));
 972                 /*
 973                  * An exec() starts a new thread group with the
 974                  * TGID of the previous thread group. Rehash the
 975                  * two threads with a switched PID, and release
 976                  * the former thread group leader:
 977                  */
 978
 979                 /* Become a process group leader with the old leader's pid.
 980                  * The old leader becomes a thread of the this thread group.
 981                  * Note: The old leader also uses this pid until release_task
 982                  *       is called.  Odd but simple and correct.
 983                  */
 984                 tsk->pid = leader->pid;
 985                 change_pid(tsk, PIDTYPE_PID, task_pid(leader));
 986                 transfer_pid(leader, tsk, PIDTYPE_PGID);
 987                 transfer_pid(leader, tsk, PIDTYPE_SID);
 988
 989                 list_replace_rcu(&leader->tasks, &tsk->tasks);
 990                 list_replace_init(&leader->sibling, &tsk->sibling);
 991
 992                 tsk->group_leader = tsk;
 993                 leader->group_leader = tsk;
 994
 995                 tsk->exit_signal = SIGCHLD;
 996                 leader->exit_signal = -1;
 997
 998                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 999                 leader->exit_state = EXIT_DEAD;
1000
1001                 /*
1002                  * We are going to release_task()->ptrace_unlink() silently,
1003                  * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1004                  * the tracer wont't block again waiting for this thread.
1005                  */
1006                 if (unlikely(leader->ptrace))
1007                         __wake_up_parent(leader, leader->parent);
1008                 write_unlock_irq(&tasklist_lock);
1009                 threadgroup_change_end(tsk);
1010
1011                 release_task(leader);
1012         }
1013
1014         sig->group_exit_task = NULL;
1015         sig->notify_count = 0;
1016
1017 no_thread_group:
1018         /* we have changed execution domain */
1019         tsk->exit_signal = SIGCHLD;
1020
1021         exit_itimers(sig);
1022         flush_itimer_signals();
1023
1024         if (atomic_read(&oldsighand->count) != 1) {
1025                 struct sighand_struct *newsighand;
1026                 /*
1027                  * This ->sighand is shared with the CLONE_SIGHAND
1028                  * but not CLONE_THREAD task, switch to the new one.
1029                  */
1030                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1031                 if (!newsighand)
1032                         return -ENOMEM;
1033
1034                 atomic_set(&newsighand->count, 1);
1035                 memcpy(newsighand->action, oldsighand->action,
1036                        sizeof(newsighand->action));
1037
1038                 write_lock_irq(&tasklist_lock);
1039                 spin_lock(&oldsighand->siglock);
1040                 rcu_assign_pointer(tsk->sighand, newsighand);
1041                 spin_unlock(&oldsighand->siglock);
1042                 write_unlock_irq(&tasklist_lock);
1043
1044                 __cleanup_sighand(oldsighand);
1045         }
1046
1047         BUG_ON(!thread_group_leader(tsk));
1048         return 0;
1049
1050 killed:
1051         /* protects against exit_notify() and __exit_signal() */
1052         read_lock(&tasklist_lock);
1053         sig->group_exit_task = NULL;
1054         sig->notify_count = 0;
1055         read_unlock(&tasklist_lock);
1056         return -EAGAIN;
1057 }
1058
1059 char *get_task_comm(char *buf, struct task_struct *tsk)
1060 {
1061         /* buf must be at least sizeof(tsk->comm) in size */
1062         task_lock(tsk);
1063         strncpy(buf, tsk->comm, sizeof(tsk->comm));
1064         task_unlock(tsk);
1065         return buf;
1066 }
1067 EXPORT_SYMBOL_GPL(get_task_comm);
1068
1069 /*
1070  * These functions flushes out all traces of the currently running executable
1071  * so that a new one can be started
1072  */
1073
1074 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1075 {
1076         task_lock(tsk);
1077         trace_task_rename(tsk, buf);
1078         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1079         task_unlock(tsk);
1080         perf_event_comm(tsk, exec);
1081 }
1082
1083 int flush_old_exec(struct linux_binprm * bprm)
1084 {
1085         int retval;
1086
1087         /*
1088          * Make sure we have a private signal table and that
1089          * we are unassociated from the previous thread group.
1090          */
1091         retval = de_thread(current);
1092         if (retval)
1093                 goto out;
1094
1095         /*
1096          * Must be called _before_ exec_mmap() as bprm->mm is
1097          * not visibile until then. This also enables the update
1098          * to be lockless.
1099          */
1100         set_mm_exe_file(bprm->mm, bprm->file);
1101
1102         /*
1103          * Release all of the old mmap stuff
1104          */
1105         acct_arg_size(bprm, 0);
1106         retval = exec_mmap(bprm->mm);
1107         if (retval)
1108                 goto out;
1109
1110         bprm->mm = NULL;                /* We're using it now */
1111
1112         set_fs(USER_DS);
1113         current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1114                                         PF_NOFREEZE | PF_NO_SETAFFINITY);
1115         flush_thread();
1116         current->personality &= ~bprm->per_clear;
1117
1118         /*
1119          * We have to apply CLOEXEC before we change whether the process is
1120          * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1121          * trying to access the should-be-closed file descriptors of a process
1122          * undergoing exec(2).
1123          */
1124         do_close_on_exec(current->files);
1125         return 0;
1126
1127 out:
1128         return retval;
1129 }
1130 EXPORT_SYMBOL(flush_old_exec);
1131
1132 void would_dump(struct linux_binprm *bprm, struct file *file)
1133 {
1134         struct inode *inode = file_inode(file);
1135         if (inode_permission2(file->f_path.mnt, inode, MAY_READ) < 0) {
1136                 struct user_namespace *old, *user_ns;
1137                 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1138
1139                 /* Ensure mm->user_ns contains the executable */
1140                 user_ns = old = bprm->mm->user_ns;
1141                 while ((user_ns != &init_user_ns) &&
1142                        !privileged_wrt_inode_uidgid(user_ns, inode))
1143                         user_ns = user_ns->parent;
1144
1145                 if (old != user_ns) {
1146                         bprm->mm->user_ns = get_user_ns(user_ns);
1147                         put_user_ns(old);
1148                 }
1149         }
1150 }
1151 EXPORT_SYMBOL(would_dump);
1152
1153 void setup_new_exec(struct linux_binprm * bprm)
1154 {
1155         arch_pick_mmap_layout(current->mm);
1156
1157         /* This is the point of no return */
1158         current->sas_ss_sp = current->sas_ss_size = 0;
1159
1160         if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid()))
1161                 set_dumpable(current->mm, SUID_DUMP_USER);
1162         else
1163                 set_dumpable(current->mm, suid_dumpable);
1164
1165         perf_event_exec();
1166         __set_task_comm(current, kbasename(bprm->filename), true);
1167
1168         /* Set the new mm task size. We have to do that late because it may
1169          * depend on TIF_32BIT which is only updated in flush_thread() on
1170          * some architectures like powerpc
1171          */
1172         current->mm->task_size = TASK_SIZE;
1173
1174         /* install the new credentials */
1175         if (!uid_eq(bprm->cred->uid, current_euid()) ||
1176             !gid_eq(bprm->cred->gid, current_egid())) {
1177                 current->pdeath_signal = 0;
1178         } else {
1179                 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
1180                         set_dumpable(current->mm, suid_dumpable);
1181         }
1182
1183         /* An exec changes our domain. We are no longer part of the thread
1184            group */
1185         current->self_exec_id++;
1186         flush_signal_handlers(current, 0);
1187 }
1188 EXPORT_SYMBOL(setup_new_exec);
1189
1190 /*
1191  * Prepare credentials and lock ->cred_guard_mutex.
1192  * install_exec_creds() commits the new creds and drops the lock.
1193  * Or, if exec fails before, free_bprm() should release ->cred and
1194  * and unlock.
1195  */
1196 int prepare_bprm_creds(struct linux_binprm *bprm)
1197 {
1198         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1199                 return -ERESTARTNOINTR;
1200
1201         bprm->cred = prepare_exec_creds();
1202         if (likely(bprm->cred))
1203                 return 0;
1204
1205         mutex_unlock(&current->signal->cred_guard_mutex);
1206         return -ENOMEM;
1207 }
1208
1209 static void free_bprm(struct linux_binprm *bprm)
1210 {
1211         free_arg_pages(bprm);
1212         if (bprm->cred) {
1213                 mutex_unlock(&current->signal->cred_guard_mutex);
1214                 abort_creds(bprm->cred);
1215         }
1216         if (bprm->file) {
1217                 allow_write_access(bprm->file);
1218                 fput(bprm->file);
1219         }
1220         /* If a binfmt changed the interp, free it. */
1221         if (bprm->interp != bprm->filename)
1222                 kfree(bprm->interp);
1223         kfree(bprm);
1224 }
1225
1226 int bprm_change_interp(char *interp, struct linux_binprm *bprm)
1227 {
1228         /* If a binfmt changed the interp, free it first. */
1229         if (bprm->interp != bprm->filename)
1230                 kfree(bprm->interp);
1231         bprm->interp = kstrdup(interp, GFP_KERNEL);
1232         if (!bprm->interp)
1233                 return -ENOMEM;
1234         return 0;
1235 }
1236 EXPORT_SYMBOL(bprm_change_interp);
1237
1238 /*
1239  * install the new credentials for this executable
1240  */
1241 void install_exec_creds(struct linux_binprm *bprm)
1242 {
1243         security_bprm_committing_creds(bprm);
1244
1245         commit_creds(bprm->cred);
1246         bprm->cred = NULL;
1247
1248         /*
1249          * Disable monitoring for regular users
1250          * when executing setuid binaries. Must
1251          * wait until new credentials are committed
1252          * by commit_creds() above
1253          */
1254         if (get_dumpable(current->mm) != SUID_DUMP_USER)
1255                 perf_event_exit_task(current);
1256         /*
1257          * cred_guard_mutex must be held at least to this point to prevent
1258          * ptrace_attach() from altering our determination of the task's
1259          * credentials; any time after this it may be unlocked.
1260          */
1261         security_bprm_committed_creds(bprm);
1262         mutex_unlock(&current->signal->cred_guard_mutex);
1263 }
1264 EXPORT_SYMBOL(install_exec_creds);
1265
1266 /*
1267  * determine how safe it is to execute the proposed program
1268  * - the caller must hold ->cred_guard_mutex to protect against
1269  *   PTRACE_ATTACH or seccomp thread-sync
1270  */
1271 static void check_unsafe_exec(struct linux_binprm *bprm)
1272 {
1273         struct task_struct *p = current, *t;
1274         unsigned n_fs;
1275
1276         if (p->ptrace) {
1277                 if (ptracer_capable(p, current_user_ns()))
1278                         bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP;
1279                 else
1280                         bprm->unsafe |= LSM_UNSAFE_PTRACE;
1281         }
1282
1283         /*
1284          * This isn't strictly necessary, but it makes it harder for LSMs to
1285          * mess up.
1286          */
1287         if (task_no_new_privs(current))
1288                 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1289
1290         t = p;
1291         n_fs = 1;
1292         spin_lock(&p->fs->lock);
1293         rcu_read_lock();
1294         while_each_thread(p, t) {
1295                 if (t->fs == p->fs)
1296                         n_fs++;
1297         }
1298         rcu_read_unlock();
1299
1300         if (p->fs->users > n_fs)
1301                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1302         else
1303                 p->fs->in_exec = 1;
1304         spin_unlock(&p->fs->lock);
1305 }
1306
1307 static void bprm_fill_uid(struct linux_binprm *bprm)
1308 {
1309         struct inode *inode;
1310         unsigned int mode;
1311         kuid_t uid;
1312         kgid_t gid;
1313
1314         /* clear any previous set[ug]id data from a previous binary */
1315         bprm->cred->euid = current_euid();
1316         bprm->cred->egid = current_egid();
1317
1318         if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
1319                 return;
1320
1321         if (task_no_new_privs(current))
1322                 return;
1323
1324         inode = file_inode(bprm->file);
1325         mode = READ_ONCE(inode->i_mode);
1326         if (!(mode & (S_ISUID|S_ISGID)))
1327                 return;
1328
1329         /* Be careful if suid/sgid is set */
1330         mutex_lock(&inode->i_mutex);
1331
1332         /* reload atomically mode/uid/gid now that lock held */
1333         mode = inode->i_mode;
1334         uid = inode->i_uid;
1335         gid = inode->i_gid;
1336         mutex_unlock(&inode->i_mutex);
1337
1338         /* We ignore suid/sgid if there are no mappings for them in the ns */
1339         if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1340                  !kgid_has_mapping(bprm->cred->user_ns, gid))
1341                 return;
1342
1343         if (mode & S_ISUID) {
1344                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1345                 bprm->cred->euid = uid;
1346         }
1347
1348         if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1349                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1350                 bprm->cred->egid = gid;
1351         }
1352 }
1353
1354 /*
1355  * Fill the binprm structure from the inode.
1356  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1357  *
1358  * This may be called multiple times for binary chains (scripts for example).
1359  */
1360 int prepare_binprm(struct linux_binprm *bprm)
1361 {
1362         int retval;
1363
1364         bprm_fill_uid(bprm);
1365
1366         /* fill in binprm security blob */
1367         retval = security_bprm_set_creds(bprm);
1368         if (retval)
1369                 return retval;
1370         bprm->cred_prepared = 1;
1371
1372         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1373         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1374 }
1375
1376 EXPORT_SYMBOL(prepare_binprm);
1377
1378 /*
1379  * Arguments are '\0' separated strings found at the location bprm->p
1380  * points to; chop off the first by relocating brpm->p to right after
1381  * the first '\0' encountered.
1382  */
1383 int remove_arg_zero(struct linux_binprm *bprm)
1384 {
1385         int ret = 0;
1386         unsigned long offset;
1387         char *kaddr;
1388         struct page *page;
1389
1390         if (!bprm->argc)
1391                 return 0;
1392
1393         do {
1394                 offset = bprm->p & ~PAGE_MASK;
1395                 page = get_arg_page(bprm, bprm->p, 0);
1396                 if (!page) {
1397                         ret = -EFAULT;
1398                         goto out;
1399                 }
1400                 kaddr = kmap_atomic(page);
1401
1402                 for (; offset < PAGE_SIZE && kaddr[offset];
1403                                 offset++, bprm->p++)
1404                         ;
1405
1406                 kunmap_atomic(kaddr);
1407                 put_arg_page(page);
1408
1409                 if (offset == PAGE_SIZE)
1410                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1411         } while (offset == PAGE_SIZE);
1412
1413         bprm->p++;
1414         bprm->argc--;
1415         ret = 0;
1416
1417 out:
1418         return ret;
1419 }
1420 EXPORT_SYMBOL(remove_arg_zero);
1421
1422 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1423 /*
1424  * cycle the list of binary formats handler, until one recognizes the image
1425  */
1426 int search_binary_handler(struct linux_binprm *bprm)
1427 {
1428         bool need_retry = IS_ENABLED(CONFIG_MODULES);
1429         struct linux_binfmt *fmt;
1430         int retval;
1431
1432         /* This allows 4 levels of binfmt rewrites before failing hard. */
1433         if (bprm->recursion_depth > 5)
1434                 return -ELOOP;
1435
1436         retval = security_bprm_check(bprm);
1437         if (retval)
1438                 return retval;
1439
1440         retval = -ENOENT;
1441  retry:
1442         read_lock(&binfmt_lock);
1443         list_for_each_entry(fmt, &formats, lh) {
1444                 if (!try_module_get(fmt->module))
1445                         continue;
1446                 read_unlock(&binfmt_lock);
1447                 bprm->recursion_depth++;
1448                 retval = fmt->load_binary(bprm);
1449                 read_lock(&binfmt_lock);
1450                 put_binfmt(fmt);
1451                 bprm->recursion_depth--;
1452                 if (retval < 0 && !bprm->mm) {
1453                         /* we got to flush_old_exec() and failed after it */
1454                         read_unlock(&binfmt_lock);
1455                         force_sigsegv(SIGSEGV, current);
1456                         return retval;
1457                 }
1458                 if (retval != -ENOEXEC || !bprm->file) {
1459                         read_unlock(&binfmt_lock);
1460                         return retval;
1461                 }
1462         }
1463         read_unlock(&binfmt_lock);
1464
1465         if (need_retry) {
1466                 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1467                     printable(bprm->buf[2]) && printable(bprm->buf[3]))
1468                         return retval;
1469                 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1470                         return retval;
1471                 need_retry = false;
1472                 goto retry;
1473         }
1474
1475         return retval;
1476 }
1477 EXPORT_SYMBOL(search_binary_handler);
1478
1479 static int exec_binprm(struct linux_binprm *bprm)
1480 {
1481         pid_t old_pid, old_vpid;
1482         int ret;
1483
1484         /* Need to fetch pid before load_binary changes it */
1485         old_pid = current->pid;
1486         rcu_read_lock();
1487         old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1488         rcu_read_unlock();
1489
1490         ret = search_binary_handler(bprm);
1491         if (ret >= 0) {
1492                 audit_bprm(bprm);
1493                 trace_sched_process_exec(current, old_pid, bprm);
1494                 ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1495                 proc_exec_connector(current);
1496         }
1497
1498         return ret;
1499 }
1500
1501 /*
1502  * sys_execve() executes a new program.
1503  */
1504 static int do_execveat_common(int fd, struct filename *filename,
1505                               struct user_arg_ptr argv,
1506                               struct user_arg_ptr envp,
1507                               int flags)
1508 {
1509         char *pathbuf = NULL;
1510         struct linux_binprm *bprm;
1511         struct file *file;
1512         struct files_struct *displaced;
1513         int retval;
1514
1515         if (IS_ERR(filename))
1516                 return PTR_ERR(filename);
1517
1518         /*
1519          * We move the actual failure in case of RLIMIT_NPROC excess from
1520          * set*uid() to execve() because too many poorly written programs
1521          * don't check setuid() return code.  Here we additionally recheck
1522          * whether NPROC limit is still exceeded.
1523          */
1524         if ((current->flags & PF_NPROC_EXCEEDED) &&
1525             atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1526                 retval = -EAGAIN;
1527                 goto out_ret;
1528         }
1529
1530         /* We're below the limit (still or again), so we don't want to make
1531          * further execve() calls fail. */
1532         current->flags &= ~PF_NPROC_EXCEEDED;
1533
1534         retval = unshare_files(&displaced);
1535         if (retval)
1536                 goto out_ret;
1537
1538         retval = -ENOMEM;
1539         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1540         if (!bprm)
1541                 goto out_files;
1542
1543         retval = prepare_bprm_creds(bprm);
1544         if (retval)
1545                 goto out_free;
1546
1547         check_unsafe_exec(bprm);
1548         current->in_execve = 1;
1549
1550         file = do_open_execat(fd, filename, flags);
1551         retval = PTR_ERR(file);
1552         if (IS_ERR(file))
1553                 goto out_unmark;
1554
1555         sched_exec();
1556
1557         bprm->file = file;
1558         if (fd == AT_FDCWD || filename->name[0] == '/') {
1559                 bprm->filename = filename->name;
1560         } else {
1561                 if (filename->name[0] == '\0')
1562                         pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d", fd);
1563                 else
1564                         pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d/%s",
1565                                             fd, filename->name);
1566                 if (!pathbuf) {
1567                         retval = -ENOMEM;
1568                         goto out_unmark;
1569                 }
1570                 /*
1571                  * Record that a name derived from an O_CLOEXEC fd will be
1572                  * inaccessible after exec. Relies on having exclusive access to
1573                  * current->files (due to unshare_files above).
1574                  */
1575                 if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
1576                         bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1577                 bprm->filename = pathbuf;
1578         }
1579         bprm->interp = bprm->filename;
1580
1581         retval = bprm_mm_init(bprm);
1582         if (retval)
1583                 goto out_unmark;
1584
1585         bprm->argc = count(argv, MAX_ARG_STRINGS);
1586         if ((retval = bprm->argc) < 0)
1587                 goto out;
1588
1589         bprm->envc = count(envp, MAX_ARG_STRINGS);
1590         if ((retval = bprm->envc) < 0)
1591                 goto out;
1592
1593         retval = prepare_binprm(bprm);
1594         if (retval < 0)
1595                 goto out;
1596
1597         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1598         if (retval < 0)
1599                 goto out;
1600
1601         bprm->exec = bprm->p;
1602         retval = copy_strings(bprm->envc, envp, bprm);
1603         if (retval < 0)
1604                 goto out;
1605
1606         retval = copy_strings(bprm->argc, argv, bprm);
1607         if (retval < 0)
1608                 goto out;
1609
1610         would_dump(bprm, bprm->file);
1611
1612         retval = exec_binprm(bprm);
1613         if (retval < 0)
1614                 goto out;
1615
1616         /* execve succeeded */
1617         current->fs->in_exec = 0;
1618         current->in_execve = 0;
1619         acct_update_integrals(current);
1620         task_numa_free(current);
1621         free_bprm(bprm);
1622         kfree(pathbuf);
1623         putname(filename);
1624         if (displaced)
1625                 put_files_struct(displaced);
1626         return retval;
1627
1628 out:
1629         if (bprm->mm) {
1630                 acct_arg_size(bprm, 0);
1631                 mmput(bprm->mm);
1632         }
1633
1634 out_unmark:
1635         current->fs->in_exec = 0;
1636         current->in_execve = 0;
1637
1638 out_free:
1639         free_bprm(bprm);
1640         kfree(pathbuf);
1641
1642 out_files:
1643         if (displaced)
1644                 reset_files_struct(displaced);
1645 out_ret:
1646         putname(filename);
1647         return retval;
1648 }
1649
1650 int do_execve(struct filename *filename,
1651         const char __user *const __user *__argv,
1652         const char __user *const __user *__envp)
1653 {
1654         struct user_arg_ptr argv = { .ptr.native = __argv };
1655         struct user_arg_ptr envp = { .ptr.native = __envp };
1656         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1657 }
1658
1659 int do_execveat(int fd, struct filename *filename,
1660                 const char __user *const __user *__argv,
1661                 const char __user *const __user *__envp,
1662                 int flags)
1663 {
1664         struct user_arg_ptr argv = { .ptr.native = __argv };
1665         struct user_arg_ptr envp = { .ptr.native = __envp };
1666
1667         return do_execveat_common(fd, filename, argv, envp, flags);
1668 }
1669
1670 #ifdef CONFIG_COMPAT
1671 static int compat_do_execve(struct filename *filename,
1672         const compat_uptr_t __user *__argv,
1673         const compat_uptr_t __user *__envp)
1674 {
1675         struct user_arg_ptr argv = {
1676                 .is_compat = true,
1677                 .ptr.compat = __argv,
1678         };
1679         struct user_arg_ptr envp = {
1680                 .is_compat = true,
1681                 .ptr.compat = __envp,
1682         };
1683         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1684 }
1685
1686 static int compat_do_execveat(int fd, struct filename *filename,
1687                               const compat_uptr_t __user *__argv,
1688                               const compat_uptr_t __user *__envp,
1689                               int flags)
1690 {
1691         struct user_arg_ptr argv = {
1692                 .is_compat = true,
1693                 .ptr.compat = __argv,
1694         };
1695         struct user_arg_ptr envp = {
1696                 .is_compat = true,
1697                 .ptr.compat = __envp,
1698         };
1699         return do_execveat_common(fd, filename, argv, envp, flags);
1700 }
1701 #endif
1702
1703 void set_binfmt(struct linux_binfmt *new)
1704 {
1705         struct mm_struct *mm = current->mm;
1706
1707         if (mm->binfmt)
1708                 module_put(mm->binfmt->module);
1709
1710         mm->binfmt = new;
1711         if (new)
1712                 __module_get(new->module);
1713 }
1714 EXPORT_SYMBOL(set_binfmt);
1715
1716 /*
1717  * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
1718  */
1719 void set_dumpable(struct mm_struct *mm, int value)
1720 {
1721         unsigned long old, new;
1722
1723         if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
1724                 return;
1725
1726         do {
1727                 old = ACCESS_ONCE(mm->flags);
1728                 new = (old & ~MMF_DUMPABLE_MASK) | value;
1729         } while (cmpxchg(&mm->flags, old, new) != old);
1730 }
1731
1732 SYSCALL_DEFINE3(execve,
1733                 const char __user *, filename,
1734                 const char __user *const __user *, argv,
1735                 const char __user *const __user *, envp)
1736 {
1737         return do_execve(getname(filename), argv, envp);
1738 }
1739
1740 SYSCALL_DEFINE5(execveat,
1741                 int, fd, const char __user *, filename,
1742                 const char __user *const __user *, argv,
1743                 const char __user *const __user *, envp,
1744                 int, flags)
1745 {
1746         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1747
1748         return do_execveat(fd,
1749                            getname_flags(filename, lookup_flags, NULL),
1750                            argv, envp, flags);
1751 }
1752
1753 #ifdef CONFIG_COMPAT
1754 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
1755         const compat_uptr_t __user *, argv,
1756         const compat_uptr_t __user *, envp)
1757 {
1758         return compat_do_execve(getname(filename), argv, envp);
1759 }
1760
1761 COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
1762                        const char __user *, filename,
1763                        const compat_uptr_t __user *, argv,
1764                        const compat_uptr_t __user *, envp,
1765                        int,  flags)
1766 {
1767         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1768
1769         return compat_do_execveat(fd,
1770                                   getname_flags(filename, lookup_flags, NULL),
1771                                   argv, envp, flags);
1772 }
1773 #endif