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