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                 unsigned long ptr_size;
 210                 struct rlimit *rlim;
 211
 212                 /*
 213                  * Since the stack will hold pointers to the strings, we
 214                  * must account for them as well.
 215                  *
 216                  * The size calculation is the entire vma while each arg page is
 217                  * built, so each time we get here it's calculating how far it
 218                  * is currently (rather than each call being just the newly
 219                  * added size from the arg page).  As a result, we need to
 220                  * always add the entire size of the pointers, so that on the
 221                  * last call to get_arg_page() we'll actually have the entire
 222                  * correct size.
 223                  */
 224                 ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
 225                 if (ptr_size > ULONG_MAX - size)
 226                         goto fail;
 227                 size += ptr_size;
 228
 229                 acct_arg_size(bprm, size / PAGE_SIZE);
 230
 231                 /*
 232                  * We've historically supported up to 32 pages (ARG_MAX)
 233                  * of argument strings even with small stacks
 234                  */
 235                 if (size <= ARG_MAX)
 236                         return page;
 237
 238                 /*
 239                  * Limit to 1/4-th the stack size for the argv+env strings.
 240                  * This ensures that:
 241                  *  - the remaining binfmt code will not run out of stack space,
 242                  *  - the program will have a reasonable amount of stack left
 243                  *    to work from.
 244                  */
 245                 rlim = current->signal->rlim;
 246                 if (size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4)
 247                         goto fail;
 248         }
 249
 250         return page;
 251
 252 fail:
 253         put_page(page);
 254         return NULL;
 255 }
 256
 257 static void put_arg_page(struct page *page)
 258 {
 259         put_page(page);
 260 }
 261
 262 static void free_arg_page(struct linux_binprm *bprm, int i)
 263 {
 264 }
 265
 266 static void free_arg_pages(struct linux_binprm *bprm)
 267 {
 268 }
 269
 270 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 271                 struct page *page)
 272 {
 273         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 274 }
 275
 276 static int __bprm_mm_init(struct linux_binprm *bprm)
 277 {
 278         int err;
 279         struct vm_area_struct *vma = NULL;
 280         struct mm_struct *mm = bprm->mm;
 281
 282         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 283         if (!vma)
 284                 return -ENOMEM;
 285
 286         down_write(&mm->mmap_sem);
 287         vma->vm_mm = mm;
 288
 289         /*
 290          * Place the stack at the largest stack address the architecture
 291          * supports. Later, we'll move this to an appropriate place. We don't
 292          * use STACK_TOP because that can depend on attributes which aren't
 293          * configured yet.
 294          */
 295         BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 296         vma->vm_end = STACK_TOP_MAX;
 297         vma->vm_start = vma->vm_end - PAGE_SIZE;
 298         vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 299         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 300         INIT_LIST_HEAD(&vma->anon_vma_chain);
 301
 302         err = insert_vm_struct(mm, vma);
 303         if (err)
 304                 goto err;
 305
 306         mm->stack_vm = mm->total_vm = 1;
 307         arch_bprm_mm_init(mm, vma);
 308         up_write(&mm->mmap_sem);
 309         bprm->p = vma->vm_end - sizeof(void *);
 310         return 0;
 311 err:
 312         up_write(&mm->mmap_sem);
 313         bprm->vma = NULL;
 314         kmem_cache_free(vm_area_cachep, vma);
 315         return err;
 316 }
 317
 318 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 319 {
 320         return len <= MAX_ARG_STRLEN;
 321 }
 322
 323 #else
 324
 325 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 326 {
 327 }
 328
 329 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 330                 int write)
 331 {
 332         struct page *page;
 333
 334         page = bprm->page[pos / PAGE_SIZE];
 335         if (!page && write) {
 336                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 337                 if (!page)
 338                         return NULL;
 339                 bprm->page[pos / PAGE_SIZE] = page;
 340         }
 341
 342         return page;
 343 }
 344
 345 static void put_arg_page(struct page *page)
 346 {
 347 }
 348
 349 static void free_arg_page(struct linux_binprm *bprm, int i)
 350 {
 351         if (bprm->page[i]) {
 352                 __free_page(bprm->page[i]);
 353                 bprm->page[i] = NULL;
 354         }
 355 }
 356
 357 static void free_arg_pages(struct linux_binprm *bprm)
 358 {
 359         int i;
 360
 361         for (i = 0; i < MAX_ARG_PAGES; i++)
 362                 free_arg_page(bprm, i);
 363 }
 364
 365 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 366                 struct page *page)
 367 {
 368 }
 369
 370 static int __bprm_mm_init(struct linux_binprm *bprm)
 371 {
 372         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 373         return 0;
 374 }
 375
 376 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 377 {
 378         return len <= bprm->p;
 379 }
 380
 381 #endif /* CONFIG_MMU */
 382
 383 /*
 384  * Create a new mm_struct and populate it with a temporary stack
 385  * vm_area_struct.  We don't have enough context at this point to set the stack
 386  * flags, permissions, and offset, so we use temporary values.  We'll update
 387  * them later in setup_arg_pages().
 388  */
 389 static int bprm_mm_init(struct linux_binprm *bprm)
 390 {
 391         int err;
 392         struct mm_struct *mm = NULL;
 393
 394         bprm->mm = mm = mm_alloc();
 395         err = -ENOMEM;
 396         if (!mm)
 397                 goto err;
 398
 399         err = __bprm_mm_init(bprm);
 400         if (err)
 401                 goto err;
 402
 403         return 0;
 404
 405 err:
 406         if (mm) {
 407                 bprm->mm = NULL;
 408                 mmdrop(mm);
 409         }
 410
 411         return err;
 412 }
 413
 414 struct user_arg_ptr {
 415 #ifdef CONFIG_COMPAT
 416         bool is_compat;
 417 #endif
 418         union {
 419                 const char __user *const __user *native;
 420 #ifdef CONFIG_COMPAT
 421                 const compat_uptr_t __user *compat;
 422 #endif
 423         } ptr;
 424 };
 425
 426 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
 427 {
 428         const char __user *native;
 429
 430 #ifdef CONFIG_COMPAT
 431         if (unlikely(argv.is_compat)) {
 432                 compat_uptr_t compat;
 433
 434                 if (get_user(compat, argv.ptr.compat + nr))
 435                         return ERR_PTR(-EFAULT);
 436
 437                 return compat_ptr(compat);
 438         }
 439 #endif
 440
 441         if (get_user(native, argv.ptr.native + nr))
 442                 return ERR_PTR(-EFAULT);
 443
 444         return native;
 445 }
 446
 447 /*
 448  * count() counts the number of strings in array ARGV.
 449  */
 450 static int count(struct user_arg_ptr argv, int max)
 451 {
 452         int i = 0;
 453
 454         if (argv.ptr.native != NULL) {
 455                 for (;;) {
 456                         const char __user *p = get_user_arg_ptr(argv, i);
 457
 458                         if (!p)
 459                                 break;
 460
 461                         if (IS_ERR(p))
 462                                 return -EFAULT;
 463
 464                         if (i >= max)
 465                                 return -E2BIG;
 466                         ++i;
 467
 468                         if (fatal_signal_pending(current))
 469                                 return -ERESTARTNOHAND;
 470                         cond_resched();
 471                 }
 472         }
 473         return i;
 474 }
 475
 476 /*
 477  * 'copy_strings()' copies argument/environment strings from the old
 478  * processes's memory to the new process's stack.  The call to get_user_pages()
 479  * ensures the destination page is created and not swapped out.
 480  */
 481 static int copy_strings(int argc, struct user_arg_ptr argv,
 482                         struct linux_binprm *bprm)
 483 {
 484         struct page *kmapped_page = NULL;
 485         char *kaddr = NULL;
 486         unsigned long kpos = 0;
 487         int ret;
 488
 489         while (argc-- > 0) {
 490                 const char __user *str;
 491                 int len;
 492                 unsigned long pos;
 493
 494                 ret = -EFAULT;
 495                 str = get_user_arg_ptr(argv, argc);
 496                 if (IS_ERR(str))
 497                         goto out;
 498
 499                 len = strnlen_user(str, MAX_ARG_STRLEN);
 500                 if (!len)
 501                         goto out;
 502
 503                 ret = -E2BIG;
 504                 if (!valid_arg_len(bprm, len))
 505                         goto out;
 506
 507                 /* We're going to work our way backwords. */
 508                 pos = bprm->p;
 509                 str += len;
 510                 bprm->p -= len;
 511
 512                 while (len > 0) {
 513                         int offset, bytes_to_copy;
 514
 515                         if (fatal_signal_pending(current)) {
 516                                 ret = -ERESTARTNOHAND;
 517                                 goto out;
 518                         }
 519                         cond_resched();
 520
 521                         offset = pos % PAGE_SIZE;
 522                         if (offset == 0)
 523                                 offset = PAGE_SIZE;
 524
 525                         bytes_to_copy = offset;
 526                         if (bytes_to_copy > len)
 527                                 bytes_to_copy = len;
 528
 529                         offset -= bytes_to_copy;
 530                         pos -= bytes_to_copy;
 531                         str -= bytes_to_copy;
 532                         len -= bytes_to_copy;
 533
 534                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 535                                 struct page *page;
 536
 537                                 page = get_arg_page(bprm, pos, 1);
 538                                 if (!page) {
 539                                         ret = -E2BIG;
 540                                         goto out;
 541                                 }
 542
 543                                 if (kmapped_page) {
 544                                         flush_kernel_dcache_page(kmapped_page);
 545                                         kunmap(kmapped_page);
 546                                         put_arg_page(kmapped_page);
 547                                 }
 548                                 kmapped_page = page;
 549                                 kaddr = kmap(kmapped_page);
 550                                 kpos = pos & PAGE_MASK;
 551                                 flush_arg_page(bprm, kpos, kmapped_page);
 552                         }
 553                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 554                                 ret = -EFAULT;
 555                                 goto out;
 556                         }
 557                 }
 558         }
 559         ret = 0;
 560 out:
 561         if (kmapped_page) {
 562                 flush_kernel_dcache_page(kmapped_page);
 563                 kunmap(kmapped_page);
 564                 put_arg_page(kmapped_page);
 565         }
 566         return ret;
 567 }
 568
 569 /*
 570  * Like copy_strings, but get argv and its values from kernel memory.
 571  */
 572 int copy_strings_kernel(int argc, const char *const *__argv,
 573                         struct linux_binprm *bprm)
 574 {
 575         int r;
 576         mm_segment_t oldfs = get_fs();
 577         struct user_arg_ptr argv = {
 578                 .ptr.native = (const char __user *const  __user *)__argv,
 579         };
 580
 581         set_fs(KERNEL_DS);
 582         r = copy_strings(argc, argv, bprm);
 583         set_fs(oldfs);
 584
 585         return r;
 586 }
 587 EXPORT_SYMBOL(copy_strings_kernel);
 588
 589 #ifdef CONFIG_MMU
 590
 591 /*
 592  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 593  * the binfmt code determines where the new stack should reside, we shift it to
 594  * its final location.  The process proceeds as follows:
 595  *
 596  * 1) Use shift to calculate the new vma endpoints.
 597  * 2) Extend vma to cover both the old and new ranges.  This ensures the
 598  *    arguments passed to subsequent functions are consistent.
 599  * 3) Move vma's page tables to the new range.
 600  * 4) Free up any cleared pgd range.
 601  * 5) Shrink the vma to cover only the new range.
 602  */
 603 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 604 {
 605         struct mm_struct *mm = vma->vm_mm;
 606         unsigned long old_start = vma->vm_start;
 607         unsigned long old_end = vma->vm_end;
 608         unsigned long length = old_end - old_start;
 609         unsigned long new_start = old_start - shift;
 610         unsigned long new_end = old_end - shift;
 611         struct mmu_gather tlb;
 612
 613         BUG_ON(new_start > new_end);
 614
 615         /*
 616          * ensure there are no vmas between where we want to go
 617          * and where we are
 618          */
 619         if (vma != find_vma(mm, new_start))
 620                 return -EFAULT;
 621
 622         /*
 623          * cover the whole range: [new_start, old_end)
 624          */
 625         if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
 626                 return -ENOMEM;
 627
 628         /*
 629          * move the page tables downwards, on failure we rely on
 630          * process cleanup to remove whatever mess we made.
 631          */
 632         if (length != move_page_tables(vma, old_start,
 633                                        vma, new_start, length, false))
 634                 return -ENOMEM;
 635
 636         lru_add_drain();
 637         tlb_gather_mmu(&tlb, mm, old_start, old_end);
 638         if (new_end > old_start) {
 639                 /*
 640                  * when the old and new regions overlap clear from new_end.
 641                  */
 642                 free_pgd_range(&tlb, new_end, old_end, new_end,
 643                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 644         } else {
 645                 /*
 646                  * otherwise, clean from old_start; this is done to not touch
 647                  * the address space in [new_end, old_start) some architectures
 648                  * have constraints on va-space that make this illegal (IA64) -
 649                  * for the others its just a little faster.
 650                  */
 651                 free_pgd_range(&tlb, old_start, old_end, new_end,
 652                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 653         }
 654         tlb_finish_mmu(&tlb, old_start, old_end);
 655
 656         /*
 657          * Shrink the vma to just the new range.  Always succeeds.
 658          */
 659         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 660
 661         return 0;
 662 }
 663
 664 /*
 665  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 666  * the stack is optionally relocated, and some extra space is added.
 667  */
 668 int setup_arg_pages(struct linux_binprm *bprm,
 669                     unsigned long stack_top,
 670                     int executable_stack)
 671 {
 672         unsigned long ret;
 673         unsigned long stack_shift;
 674         struct mm_struct *mm = current->mm;
 675         struct vm_area_struct *vma = bprm->vma;
 676         struct vm_area_struct *prev = NULL;
 677         unsigned long vm_flags;
 678         unsigned long stack_base;
 679         unsigned long stack_size;
 680         unsigned long stack_expand;
 681         unsigned long rlim_stack;
 682
 683 #ifdef CONFIG_STACK_GROWSUP
 684         /* Limit stack size */
 685         stack_base = rlimit_max(RLIMIT_STACK);
 686         if (stack_base > STACK_SIZE_MAX)
 687                 stack_base = STACK_SIZE_MAX;
 688
 689         /* Add space for stack randomization. */
 690         stack_base += (STACK_RND_MASK << PAGE_SHIFT);
 691
 692         /* Make sure we didn't let the argument array grow too large. */
 693         if (vma->vm_end - vma->vm_start > stack_base)
 694                 return -ENOMEM;
 695
 696         stack_base = PAGE_ALIGN(stack_top - stack_base);
 697
 698         stack_shift = vma->vm_start - stack_base;
 699         mm->arg_start = bprm->p - stack_shift;
 700         bprm->p = vma->vm_end - stack_shift;
 701 #else
 702         stack_top = arch_align_stack(stack_top);
 703         stack_top = PAGE_ALIGN(stack_top);
 704
 705         if (unlikely(stack_top < mmap_min_addr) ||
 706             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 707                 return -ENOMEM;
 708
 709         stack_shift = vma->vm_end - stack_top;
 710
 711         bprm->p -= stack_shift;
 712         mm->arg_start = bprm->p;
 713 #endif
 714
 715         if (bprm->loader)
 716                 bprm->loader -= stack_shift;
 717         bprm->exec -= stack_shift;
 718
 719         down_write(&mm->mmap_sem);
 720         vm_flags = VM_STACK_FLAGS;
 721
 722         /*
 723          * Adjust stack execute permissions; explicitly enable for
 724          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 725          * (arch default) otherwise.
 726          */
 727         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 728                 vm_flags |= VM_EXEC;
 729         else if (executable_stack == EXSTACK_DISABLE_X)
 730                 vm_flags &= ~VM_EXEC;
 731         vm_flags |= mm->def_flags;
 732         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 733
 734         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 735                         vm_flags);
 736         if (ret)
 737                 goto out_unlock;
 738         BUG_ON(prev != vma);
 739
 740         /* Move stack pages down in memory. */
 741         if (stack_shift) {
 742                 ret = shift_arg_pages(vma, stack_shift);
 743                 if (ret)
 744                         goto out_unlock;
 745         }
 746
 747         /* mprotect_fixup is overkill to remove the temporary stack flags */
 748         vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
 749
 750         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
 751         stack_size = vma->vm_end - vma->vm_start;
 752         /*
 753          * Align this down to a page boundary as expand_stack
 754          * will align it up.
 755          */
 756         rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 757 #ifdef CONFIG_STACK_GROWSUP
 758         if (stack_size + stack_expand > rlim_stack)
 759                 stack_base = vma->vm_start + rlim_stack;
 760         else
 761                 stack_base = vma->vm_end + stack_expand;
 762 #else
 763         if (stack_size + stack_expand > rlim_stack)
 764                 stack_base = vma->vm_end - rlim_stack;
 765         else
 766                 stack_base = vma->vm_start - stack_expand;
 767 #endif
 768         current->mm->start_stack = bprm->p;
 769         ret = expand_stack(vma, stack_base);
 770         if (ret)
 771                 ret = -EFAULT;
 772
 773 out_unlock:
 774         up_write(&mm->mmap_sem);
 775         return ret;
 776 }
 777 EXPORT_SYMBOL(setup_arg_pages);
 778
 779 #endif /* CONFIG_MMU */
 780
 781 static struct file *do_open_execat(int fd, struct filename *name, int flags)
 782 {
 783         struct file *file;
 784         int err;
 785         struct open_flags open_exec_flags = {
 786                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 787                 .acc_mode = MAY_EXEC | MAY_OPEN,
 788                 .intent = LOOKUP_OPEN,
 789                 .lookup_flags = LOOKUP_FOLLOW,
 790         };
 791
 792         if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 793                 return ERR_PTR(-EINVAL);
 794         if (flags & AT_SYMLINK_NOFOLLOW)
 795                 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
 796         if (flags & AT_EMPTY_PATH)
 797                 open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
 798
 799         file = do_filp_open(fd, name, &open_exec_flags);
 800         if (IS_ERR(file))
 801                 goto out;
 802
 803         err = -EACCES;
 804         if (!S_ISREG(file_inode(file)->i_mode))
 805                 goto exit;
 806
 807         if (path_noexec(&file->f_path))
 808                 goto exit;
 809
 810         err = deny_write_access(file);
 811         if (err)
 812                 goto exit;
 813
 814         if (name->name[0] != '\0')
 815                 fsnotify_open(file);
 816
 817 out:
 818         return file;
 819
 820 exit:
 821         fput(file);
 822         return ERR_PTR(err);
 823 }
 824
 825 struct file *open_exec(const char *name)
 826 {
 827         struct filename *filename = getname_kernel(name);
 828         struct file *f = ERR_CAST(filename);
 829
 830         if (!IS_ERR(filename)) {
 831                 f = do_open_execat(AT_FDCWD, filename, 0);
 832                 putname(filename);
 833         }
 834         return f;
 835 }
 836 EXPORT_SYMBOL(open_exec);
 837
 838 int kernel_read(struct file *file, loff_t offset,
 839                 char *addr, unsigned long count)
 840 {
 841         mm_segment_t old_fs;
 842         loff_t pos = offset;
 843         int result;
 844
 845         old_fs = get_fs();
 846         set_fs(get_ds());
 847         /* The cast to a user pointer is valid due to the set_fs() */
 848         result = vfs_read(file, (void __user *)addr, count, &pos);
 849         set_fs(old_fs);
 850         return result;
 851 }
 852
 853 EXPORT_SYMBOL(kernel_read);
 854
 855 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
 856 {
 857         ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
 858         if (res > 0)
 859                 flush_icache_range(addr, addr + len);
 860         return res;
 861 }
 862 EXPORT_SYMBOL(read_code);
 863
 864 static int exec_mmap(struct mm_struct *mm)
 865 {
 866         struct task_struct *tsk;
 867         struct mm_struct *old_mm, *active_mm;
 868
 869         /* Notify parent that we're no longer interested in the old VM */
 870         tsk = current;
 871         old_mm = current->mm;
 872         mm_release(tsk, old_mm);
 873
 874         if (old_mm) {
 875                 sync_mm_rss(old_mm);
 876                 /*
 877                  * Make sure that if there is a core dump in progress
 878                  * for the old mm, we get out and die instead of going
 879                  * through with the exec.  We must hold mmap_sem around
 880                  * checking core_state and changing tsk->mm.
 881                  */
 882                 down_read(&old_mm->mmap_sem);
 883                 if (unlikely(old_mm->core_state)) {
 884                         up_read(&old_mm->mmap_sem);
 885                         return -EINTR;
 886                 }
 887         }
 888         task_lock(tsk);
 889         active_mm = tsk->active_mm;
 890         tsk->mm = mm;
 891         tsk->active_mm = mm;
 892         activate_mm(active_mm, mm);
 893         tsk->mm->vmacache_seqnum = 0;
 894         vmacache_flush(tsk);
 895         task_unlock(tsk);
 896         if (old_mm) {
 897                 up_read(&old_mm->mmap_sem);
 898                 BUG_ON(active_mm != old_mm);
 899                 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
 900                 mm_update_next_owner(old_mm);
 901                 mmput(old_mm);
 902                 return 0;
 903         }
 904         mmdrop(active_mm);
 905         return 0;
 906 }
 907
 908 /*
 909  * This function makes sure the current process has its own signal table,
 910  * so that flush_signal_handlers can later reset the handlers without
 911  * disturbing other processes.  (Other processes might share the signal
 912  * table via the CLONE_SIGHAND option to clone().)
 913  */
 914 static int de_thread(struct task_struct *tsk)
 915 {
 916         struct signal_struct *sig = tsk->signal;
 917         struct sighand_struct *oldsighand = tsk->sighand;
 918         spinlock_t *lock = &oldsighand->siglock;
 919
 920         if (thread_group_empty(tsk))
 921                 goto no_thread_group;
 922
 923         /*
 924          * Kill all other threads in the thread group.
 925          */
 926         spin_lock_irq(lock);
 927         if (signal_group_exit(sig)) {
 928                 /*
 929                  * Another group action in progress, just
 930                  * return so that the signal is processed.
 931                  */
 932                 spin_unlock_irq(lock);
 933                 return -EAGAIN;
 934         }
 935
 936         sig->group_exit_task = tsk;
 937         sig->notify_count = zap_other_threads(tsk);
 938         if (!thread_group_leader(tsk))
 939                 sig->notify_count--;
 940
 941         while (sig->notify_count) {
 942                 __set_current_state(TASK_KILLABLE);
 943                 spin_unlock_irq(lock);
 944                 schedule();
 945                 if (unlikely(__fatal_signal_pending(tsk)))
 946                         goto killed;
 947                 spin_lock_irq(lock);
 948         }
 949         spin_unlock_irq(lock);
 950
 951         /*
 952          * At this point all other threads have exited, all we have to
 953          * do is to wait for the thread group leader to become inactive,
 954          * and to assume its PID:
 955          */
 956         if (!thread_group_leader(tsk)) {
 957                 struct task_struct *leader = tsk->group_leader;
 958
 959                 for (;;) {
 960                         threadgroup_change_begin(tsk);
 961                         write_lock_irq(&tasklist_lock);
 962                         /*
 963                          * Do this under tasklist_lock to ensure that
 964                          * exit_notify() can't miss ->group_exit_task
 965                          */
 966                         sig->notify_count = -1;
 967                         if (likely(leader->exit_state))
 968                                 break;
 969                         __set_current_state(TASK_KILLABLE);
 970                         write_unlock_irq(&tasklist_lock);
 971                         threadgroup_change_end(tsk);
 972                         schedule();
 973                         if (unlikely(__fatal_signal_pending(tsk)))
 974                                 goto killed;
 975                 }
 976
 977                 /*
 978                  * The only record we have of the real-time age of a
 979                  * process, regardless of execs it's done, is start_time.
 980                  * All the past CPU time is accumulated in signal_struct
 981                  * from sister threads now dead.  But in this non-leader
 982                  * exec, nothing survives from the original leader thread,
 983                  * whose birth marks the true age of this process now.
 984                  * When we take on its identity by switching to its PID, we
 985                  * also take its birthdate (always earlier than our own).
 986                  */
 987                 tsk->start_time = leader->start_time;
 988                 tsk->real_start_time = leader->real_start_time;
 989
 990                 BUG_ON(!same_thread_group(leader, tsk));
 991                 BUG_ON(has_group_leader_pid(tsk));
 992                 /*
 993                  * An exec() starts a new thread group with the
 994                  * TGID of the previous thread group. Rehash the
 995                  * two threads with a switched PID, and release
 996                  * the former thread group leader:
 997                  */
 998
 999                 /* Become a process group leader with the old leader's pid.
1000                  * The old leader becomes a thread of the this thread group.
1001                  * Note: The old leader also uses this pid until release_task
1002                  *       is called.  Odd but simple and correct.
1003                  */
1004                 tsk->pid = leader->pid;
1005                 change_pid(tsk, PIDTYPE_PID, task_pid(leader));
1006                 transfer_pid(leader, tsk, PIDTYPE_PGID);
1007                 transfer_pid(leader, tsk, PIDTYPE_SID);
1008
1009                 list_replace_rcu(&leader->tasks, &tsk->tasks);
1010                 list_replace_init(&leader->sibling, &tsk->sibling);
1011
1012                 tsk->group_leader = tsk;
1013                 leader->group_leader = tsk;
1014
1015                 tsk->exit_signal = SIGCHLD;
1016                 leader->exit_signal = -1;
1017
1018                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1019                 leader->exit_state = EXIT_DEAD;
1020
1021                 /*
1022                  * We are going to release_task()->ptrace_unlink() silently,
1023                  * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1024                  * the tracer wont't block again waiting for this thread.
1025                  */
1026                 if (unlikely(leader->ptrace))
1027                         __wake_up_parent(leader, leader->parent);
1028                 write_unlock_irq(&tasklist_lock);
1029                 threadgroup_change_end(tsk);
1030
1031                 release_task(leader);
1032         }
1033
1034         sig->group_exit_task = NULL;
1035         sig->notify_count = 0;
1036
1037 no_thread_group:
1038         /* we have changed execution domain */
1039         tsk->exit_signal = SIGCHLD;
1040
1041         exit_itimers(sig);
1042         flush_itimer_signals();
1043
1044         if (atomic_read(&oldsighand->count) != 1) {
1045                 struct sighand_struct *newsighand;
1046                 /*
1047                  * This ->sighand is shared with the CLONE_SIGHAND
1048                  * but not CLONE_THREAD task, switch to the new one.
1049                  */
1050                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1051                 if (!newsighand)
1052                         return -ENOMEM;
1053
1054                 atomic_set(&newsighand->count, 1);
1055                 memcpy(newsighand->action, oldsighand->action,
1056                        sizeof(newsighand->action));
1057
1058                 write_lock_irq(&tasklist_lock);
1059                 spin_lock(&oldsighand->siglock);
1060                 rcu_assign_pointer(tsk->sighand, newsighand);
1061                 spin_unlock(&oldsighand->siglock);
1062                 write_unlock_irq(&tasklist_lock);
1063
1064                 __cleanup_sighand(oldsighand);
1065         }
1066
1067         BUG_ON(!thread_group_leader(tsk));
1068         return 0;
1069
1070 killed:
1071         /* protects against exit_notify() and __exit_signal() */
1072         read_lock(&tasklist_lock);
1073         sig->group_exit_task = NULL;
1074         sig->notify_count = 0;
1075         read_unlock(&tasklist_lock);
1076         return -EAGAIN;
1077 }
1078
1079 char *get_task_comm(char *buf, struct task_struct *tsk)
1080 {
1081         /* buf must be at least sizeof(tsk->comm) in size */
1082         task_lock(tsk);
1083         strncpy(buf, tsk->comm, sizeof(tsk->comm));
1084         task_unlock(tsk);
1085         return buf;
1086 }
1087 EXPORT_SYMBOL_GPL(get_task_comm);
1088
1089 /*
1090  * These functions flushes out all traces of the currently running executable
1091  * so that a new one can be started
1092  */
1093
1094 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1095 {
1096         task_lock(tsk);
1097         trace_task_rename(tsk, buf);
1098         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1099         task_unlock(tsk);
1100         perf_event_comm(tsk, exec);
1101 }
1102
1103 int flush_old_exec(struct linux_binprm * bprm)
1104 {
1105         int retval;
1106
1107         /*
1108          * Make sure we have a private signal table and that
1109          * we are unassociated from the previous thread group.
1110          */
1111         retval = de_thread(current);
1112         if (retval)
1113                 goto out;
1114
1115         /*
1116          * Must be called _before_ exec_mmap() as bprm->mm is
1117          * not visibile until then. This also enables the update
1118          * to be lockless.
1119          */
1120         set_mm_exe_file(bprm->mm, bprm->file);
1121
1122         /*
1123          * Release all of the old mmap stuff
1124          */
1125         acct_arg_size(bprm, 0);
1126         retval = exec_mmap(bprm->mm);
1127         if (retval)
1128                 goto out;
1129
1130         bprm->mm = NULL;                /* We're using it now */
1131
1132         set_fs(USER_DS);
1133         current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1134                                         PF_NOFREEZE | PF_NO_SETAFFINITY);
1135         flush_thread();
1136         current->personality &= ~bprm->per_clear;
1137
1138         /*
1139          * We have to apply CLOEXEC before we change whether the process is
1140          * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1141          * trying to access the should-be-closed file descriptors of a process
1142          * undergoing exec(2).
1143          */
1144         do_close_on_exec(current->files);
1145         return 0;
1146
1147 out:
1148         return retval;
1149 }
1150 EXPORT_SYMBOL(flush_old_exec);
1151
1152 void would_dump(struct linux_binprm *bprm, struct file *file)
1153 {
1154         struct inode *inode = file_inode(file);
1155         if (inode_permission2(file->f_path.mnt, inode, MAY_READ) < 0) {
1156                 struct user_namespace *old, *user_ns;
1157                 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1158
1159                 /* Ensure mm->user_ns contains the executable */
1160                 user_ns = old = bprm->mm->user_ns;
1161                 while ((user_ns != &init_user_ns) &&
1162                        !privileged_wrt_inode_uidgid(user_ns, inode))
1163                         user_ns = user_ns->parent;
1164
1165                 if (old != user_ns) {
1166                         bprm->mm->user_ns = get_user_ns(user_ns);
1167                         put_user_ns(old);
1168                 }
1169         }
1170 }
1171 EXPORT_SYMBOL(would_dump);
1172
1173 void setup_new_exec(struct linux_binprm * bprm)
1174 {
1175         arch_pick_mmap_layout(current->mm);
1176
1177         /* This is the point of no return */
1178         current->sas_ss_sp = current->sas_ss_size = 0;
1179
1180         if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid()))
1181                 set_dumpable(current->mm, SUID_DUMP_USER);
1182         else
1183                 set_dumpable(current->mm, suid_dumpable);
1184
1185         perf_event_exec();
1186         __set_task_comm(current, kbasename(bprm->filename), true);
1187
1188         /* Set the new mm task size. We have to do that late because it may
1189          * depend on TIF_32BIT which is only updated in flush_thread() on
1190          * some architectures like powerpc
1191          */
1192         current->mm->task_size = TASK_SIZE;
1193
1194         /* install the new credentials */
1195         if (!uid_eq(bprm->cred->uid, current_euid()) ||
1196             !gid_eq(bprm->cred->gid, current_egid())) {
1197                 current->pdeath_signal = 0;
1198         } else {
1199                 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
1200                         set_dumpable(current->mm, suid_dumpable);
1201         }
1202
1203         /* An exec changes our domain. We are no longer part of the thread
1204            group */
1205         current->self_exec_id++;
1206         flush_signal_handlers(current, 0);
1207 }
1208 EXPORT_SYMBOL(setup_new_exec);
1209
1210 /*
1211  * Prepare credentials and lock ->cred_guard_mutex.
1212  * install_exec_creds() commits the new creds and drops the lock.
1213  * Or, if exec fails before, free_bprm() should release ->cred and
1214  * and unlock.
1215  */
1216 int prepare_bprm_creds(struct linux_binprm *bprm)
1217 {
1218         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1219                 return -ERESTARTNOINTR;
1220
1221         bprm->cred = prepare_exec_creds();
1222         if (likely(bprm->cred))
1223                 return 0;
1224
1225         mutex_unlock(&current->signal->cred_guard_mutex);
1226         return -ENOMEM;
1227 }
1228
1229 static void free_bprm(struct linux_binprm *bprm)
1230 {
1231         free_arg_pages(bprm);
1232         if (bprm->cred) {
1233                 mutex_unlock(&current->signal->cred_guard_mutex);
1234                 abort_creds(bprm->cred);
1235         }
1236         if (bprm->file) {
1237                 allow_write_access(bprm->file);
1238                 fput(bprm->file);
1239         }
1240         /* If a binfmt changed the interp, free it. */
1241         if (bprm->interp != bprm->filename)
1242                 kfree(bprm->interp);
1243         kfree(bprm);
1244 }
1245
1246 int bprm_change_interp(char *interp, struct linux_binprm *bprm)
1247 {
1248         /* If a binfmt changed the interp, free it first. */
1249         if (bprm->interp != bprm->filename)
1250                 kfree(bprm->interp);
1251         bprm->interp = kstrdup(interp, GFP_KERNEL);
1252         if (!bprm->interp)
1253                 return -ENOMEM;
1254         return 0;
1255 }
1256 EXPORT_SYMBOL(bprm_change_interp);
1257
1258 /*
1259  * install the new credentials for this executable
1260  */
1261 void install_exec_creds(struct linux_binprm *bprm)
1262 {
1263         security_bprm_committing_creds(bprm);
1264
1265         commit_creds(bprm->cred);
1266         bprm->cred = NULL;
1267
1268         /*
1269          * Disable monitoring for regular users
1270          * when executing setuid binaries. Must
1271          * wait until new credentials are committed
1272          * by commit_creds() above
1273          */
1274         if (get_dumpable(current->mm) != SUID_DUMP_USER)
1275                 perf_event_exit_task(current);
1276         /*
1277          * cred_guard_mutex must be held at least to this point to prevent
1278          * ptrace_attach() from altering our determination of the task's
1279          * credentials; any time after this it may be unlocked.
1280          */
1281         security_bprm_committed_creds(bprm);
1282         mutex_unlock(&current->signal->cred_guard_mutex);
1283 }
1284 EXPORT_SYMBOL(install_exec_creds);
1285
1286 /*
1287  * determine how safe it is to execute the proposed program
1288  * - the caller must hold ->cred_guard_mutex to protect against
1289  *   PTRACE_ATTACH or seccomp thread-sync
1290  */
1291 static void check_unsafe_exec(struct linux_binprm *bprm)
1292 {
1293         struct task_struct *p = current, *t;
1294         unsigned n_fs;
1295
1296         if (p->ptrace) {
1297                 if (ptracer_capable(p, current_user_ns()))
1298                         bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP;
1299                 else
1300                         bprm->unsafe |= LSM_UNSAFE_PTRACE;
1301         }
1302
1303         /*
1304          * This isn't strictly necessary, but it makes it harder for LSMs to
1305          * mess up.
1306          */
1307         if (task_no_new_privs(current))
1308                 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1309
1310         t = p;
1311         n_fs = 1;
1312         spin_lock(&p->fs->lock);
1313         rcu_read_lock();
1314         while_each_thread(p, t) {
1315                 if (t->fs == p->fs)
1316                         n_fs++;
1317         }
1318         rcu_read_unlock();
1319
1320         if (p->fs->users > n_fs)
1321                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1322         else
1323                 p->fs->in_exec = 1;
1324         spin_unlock(&p->fs->lock);
1325 }
1326
1327 static void bprm_fill_uid(struct linux_binprm *bprm)
1328 {
1329         struct inode *inode;
1330         unsigned int mode;
1331         kuid_t uid;
1332         kgid_t gid;
1333
1334         /* clear any previous set[ug]id data from a previous binary */
1335         bprm->cred->euid = current_euid();
1336         bprm->cred->egid = current_egid();
1337
1338         if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
1339                 return;
1340
1341         if (task_no_new_privs(current))
1342                 return;
1343
1344         inode = file_inode(bprm->file);
1345         mode = READ_ONCE(inode->i_mode);
1346         if (!(mode & (S_ISUID|S_ISGID)))
1347                 return;
1348
1349         /* Be careful if suid/sgid is set */
1350         mutex_lock(&inode->i_mutex);
1351
1352         /* reload atomically mode/uid/gid now that lock held */
1353         mode = inode->i_mode;
1354         uid = inode->i_uid;
1355         gid = inode->i_gid;
1356         mutex_unlock(&inode->i_mutex);
1357
1358         /* We ignore suid/sgid if there are no mappings for them in the ns */
1359         if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1360                  !kgid_has_mapping(bprm->cred->user_ns, gid))
1361                 return;
1362
1363         if (mode & S_ISUID) {
1364                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1365                 bprm->cred->euid = uid;
1366         }
1367
1368         if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1369                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1370                 bprm->cred->egid = gid;
1371         }
1372 }
1373
1374 /*
1375  * Fill the binprm structure from the inode.
1376  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1377  *
1378  * This may be called multiple times for binary chains (scripts for example).
1379  */
1380 int prepare_binprm(struct linux_binprm *bprm)
1381 {
1382         int retval;
1383
1384         bprm_fill_uid(bprm);
1385
1386         /* fill in binprm security blob */
1387         retval = security_bprm_set_creds(bprm);
1388         if (retval)
1389                 return retval;
1390         bprm->cred_prepared = 1;
1391
1392         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1393         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1394 }
1395
1396 EXPORT_SYMBOL(prepare_binprm);
1397
1398 /*
1399  * Arguments are '\0' separated strings found at the location bprm->p
1400  * points to; chop off the first by relocating brpm->p to right after
1401  * the first '\0' encountered.
1402  */
1403 int remove_arg_zero(struct linux_binprm *bprm)
1404 {
1405         int ret = 0;
1406         unsigned long offset;
1407         char *kaddr;
1408         struct page *page;
1409
1410         if (!bprm->argc)
1411                 return 0;
1412
1413         do {
1414                 offset = bprm->p & ~PAGE_MASK;
1415                 page = get_arg_page(bprm, bprm->p, 0);
1416                 if (!page) {
1417                         ret = -EFAULT;
1418                         goto out;
1419                 }
1420                 kaddr = kmap_atomic(page);
1421
1422                 for (; offset < PAGE_SIZE && kaddr[offset];
1423                                 offset++, bprm->p++)
1424                         ;
1425
1426                 kunmap_atomic(kaddr);
1427                 put_arg_page(page);
1428
1429                 if (offset == PAGE_SIZE)
1430                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1431         } while (offset == PAGE_SIZE);
1432
1433         bprm->p++;
1434         bprm->argc--;
1435         ret = 0;
1436
1437 out:
1438         return ret;
1439 }
1440 EXPORT_SYMBOL(remove_arg_zero);
1441
1442 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1443 /*
1444  * cycle the list of binary formats handler, until one recognizes the image
1445  */
1446 int search_binary_handler(struct linux_binprm *bprm)
1447 {
1448         bool need_retry = IS_ENABLED(CONFIG_MODULES);
1449         struct linux_binfmt *fmt;
1450         int retval;
1451
1452         /* This allows 4 levels of binfmt rewrites before failing hard. */
1453         if (bprm->recursion_depth > 5)
1454                 return -ELOOP;
1455
1456         retval = security_bprm_check(bprm);
1457         if (retval)
1458                 return retval;
1459
1460         retval = -ENOENT;
1461  retry:
1462         read_lock(&binfmt_lock);
1463         list_for_each_entry(fmt, &formats, lh) {
1464                 if (!try_module_get(fmt->module))
1465                         continue;
1466                 read_unlock(&binfmt_lock);
1467                 bprm->recursion_depth++;
1468                 retval = fmt->load_binary(bprm);
1469                 read_lock(&binfmt_lock);
1470                 put_binfmt(fmt);
1471                 bprm->recursion_depth--;
1472                 if (retval < 0 && !bprm->mm) {
1473                         /* we got to flush_old_exec() and failed after it */
1474                         read_unlock(&binfmt_lock);
1475                         force_sigsegv(SIGSEGV, current);
1476                         return retval;
1477                 }
1478                 if (retval != -ENOEXEC || !bprm->file) {
1479                         read_unlock(&binfmt_lock);
1480                         return retval;
1481                 }
1482         }
1483         read_unlock(&binfmt_lock);
1484
1485         if (need_retry) {
1486                 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1487                     printable(bprm->buf[2]) && printable(bprm->buf[3]))
1488                         return retval;
1489                 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1490                         return retval;
1491                 need_retry = false;
1492                 goto retry;
1493         }
1494
1495         return retval;
1496 }
1497 EXPORT_SYMBOL(search_binary_handler);
1498
1499 static int exec_binprm(struct linux_binprm *bprm)
1500 {
1501         pid_t old_pid, old_vpid;
1502         int ret;
1503
1504         /* Need to fetch pid before load_binary changes it */
1505         old_pid = current->pid;
1506         rcu_read_lock();
1507         old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1508         rcu_read_unlock();
1509
1510         ret = search_binary_handler(bprm);
1511         if (ret >= 0) {
1512                 audit_bprm(bprm);
1513                 trace_sched_process_exec(current, old_pid, bprm);
1514                 ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1515                 proc_exec_connector(current);
1516         }
1517
1518         return ret;
1519 }
1520
1521 /*
1522  * sys_execve() executes a new program.
1523  */
1524 static int do_execveat_common(int fd, struct filename *filename,
1525                               struct user_arg_ptr argv,
1526                               struct user_arg_ptr envp,
1527                               int flags)
1528 {
1529         char *pathbuf = NULL;
1530         struct linux_binprm *bprm;
1531         struct file *file;
1532         struct files_struct *displaced;
1533         int retval;
1534
1535         if (IS_ERR(filename))
1536                 return PTR_ERR(filename);
1537
1538         /*
1539          * We move the actual failure in case of RLIMIT_NPROC excess from
1540          * set*uid() to execve() because too many poorly written programs
1541          * don't check setuid() return code.  Here we additionally recheck
1542          * whether NPROC limit is still exceeded.
1543          */
1544         if ((current->flags & PF_NPROC_EXCEEDED) &&
1545             atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1546                 retval = -EAGAIN;
1547                 goto out_ret;
1548         }
1549
1550         /* We're below the limit (still or again), so we don't want to make
1551          * further execve() calls fail. */
1552         current->flags &= ~PF_NPROC_EXCEEDED;
1553
1554         retval = unshare_files(&displaced);
1555         if (retval)
1556                 goto out_ret;
1557
1558         retval = -ENOMEM;
1559         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1560         if (!bprm)
1561                 goto out_files;
1562
1563         retval = prepare_bprm_creds(bprm);
1564         if (retval)
1565                 goto out_free;
1566
1567         check_unsafe_exec(bprm);
1568         current->in_execve = 1;
1569
1570         file = do_open_execat(fd, filename, flags);
1571         retval = PTR_ERR(file);
1572         if (IS_ERR(file))
1573                 goto out_unmark;
1574
1575         sched_exec();
1576
1577         bprm->file = file;
1578         if (fd == AT_FDCWD || filename->name[0] == '/') {
1579                 bprm->filename = filename->name;
1580         } else {
1581                 if (filename->name[0] == '\0')
1582                         pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d", fd);
1583                 else
1584                         pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d/%s",
1585                                             fd, filename->name);
1586                 if (!pathbuf) {
1587                         retval = -ENOMEM;
1588                         goto out_unmark;
1589                 }
1590                 /*
1591                  * Record that a name derived from an O_CLOEXEC fd will be
1592                  * inaccessible after exec. Relies on having exclusive access to
1593                  * current->files (due to unshare_files above).
1594                  */
1595                 if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
1596                         bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1597                 bprm->filename = pathbuf;
1598         }
1599         bprm->interp = bprm->filename;
1600
1601         retval = bprm_mm_init(bprm);
1602         if (retval)
1603                 goto out_unmark;
1604
1605         bprm->argc = count(argv, MAX_ARG_STRINGS);
1606         if ((retval = bprm->argc) < 0)
1607                 goto out;
1608
1609         bprm->envc = count(envp, MAX_ARG_STRINGS);
1610         if ((retval = bprm->envc) < 0)
1611                 goto out;
1612
1613         retval = prepare_binprm(bprm);
1614         if (retval < 0)
1615                 goto out;
1616
1617         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1618         if (retval < 0)
1619                 goto out;
1620
1621         bprm->exec = bprm->p;
1622         retval = copy_strings(bprm->envc, envp, bprm);
1623         if (retval < 0)
1624                 goto out;
1625
1626         retval = copy_strings(bprm->argc, argv, bprm);
1627         if (retval < 0)
1628                 goto out;
1629
1630         would_dump(bprm, bprm->file);
1631
1632         retval = exec_binprm(bprm);
1633         if (retval < 0)
1634                 goto out;
1635
1636         /* execve succeeded */
1637         current->fs->in_exec = 0;
1638         current->in_execve = 0;
1639         acct_update_integrals(current);
1640         task_numa_free(current);
1641         free_bprm(bprm);
1642         kfree(pathbuf);
1643         putname(filename);
1644         if (displaced)
1645                 put_files_struct(displaced);
1646         return retval;
1647
1648 out:
1649         if (bprm->mm) {
1650                 acct_arg_size(bprm, 0);
1651                 mmput(bprm->mm);
1652         }
1653
1654 out_unmark:
1655         current->fs->in_exec = 0;
1656         current->in_execve = 0;
1657
1658 out_free:
1659         free_bprm(bprm);
1660         kfree(pathbuf);
1661
1662 out_files:
1663         if (displaced)
1664                 reset_files_struct(displaced);
1665 out_ret:
1666         putname(filename);
1667         return retval;
1668 }
1669
1670 int do_execve(struct filename *filename,
1671         const char __user *const __user *__argv,
1672         const char __user *const __user *__envp)
1673 {
1674         struct user_arg_ptr argv = { .ptr.native = __argv };
1675         struct user_arg_ptr envp = { .ptr.native = __envp };
1676         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1677 }
1678
1679 int do_execveat(int fd, struct filename *filename,
1680                 const char __user *const __user *__argv,
1681                 const char __user *const __user *__envp,
1682                 int flags)
1683 {
1684         struct user_arg_ptr argv = { .ptr.native = __argv };
1685         struct user_arg_ptr envp = { .ptr.native = __envp };
1686
1687         return do_execveat_common(fd, filename, argv, envp, flags);
1688 }
1689
1690 #ifdef CONFIG_COMPAT
1691 static int compat_do_execve(struct filename *filename,
1692         const compat_uptr_t __user *__argv,
1693         const compat_uptr_t __user *__envp)
1694 {
1695         struct user_arg_ptr argv = {
1696                 .is_compat = true,
1697                 .ptr.compat = __argv,
1698         };
1699         struct user_arg_ptr envp = {
1700                 .is_compat = true,
1701                 .ptr.compat = __envp,
1702         };
1703         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1704 }
1705
1706 static int compat_do_execveat(int fd, struct filename *filename,
1707                               const compat_uptr_t __user *__argv,
1708                               const compat_uptr_t __user *__envp,
1709                               int flags)
1710 {
1711         struct user_arg_ptr argv = {
1712                 .is_compat = true,
1713                 .ptr.compat = __argv,
1714         };
1715         struct user_arg_ptr envp = {
1716                 .is_compat = true,
1717                 .ptr.compat = __envp,
1718         };
1719         return do_execveat_common(fd, filename, argv, envp, flags);
1720 }
1721 #endif
1722
1723 void set_binfmt(struct linux_binfmt *new)
1724 {
1725         struct mm_struct *mm = current->mm;
1726
1727         if (mm->binfmt)
1728                 module_put(mm->binfmt->module);
1729
1730         mm->binfmt = new;
1731         if (new)
1732                 __module_get(new->module);
1733 }
1734 EXPORT_SYMBOL(set_binfmt);
1735
1736 /*
1737  * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
1738  */
1739 void set_dumpable(struct mm_struct *mm, int value)
1740 {
1741         unsigned long old, new;
1742
1743         if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
1744                 return;
1745
1746         do {
1747                 old = ACCESS_ONCE(mm->flags);
1748                 new = (old & ~MMF_DUMPABLE_MASK) | value;
1749         } while (cmpxchg(&mm->flags, old, new) != old);
1750 }
1751
1752 SYSCALL_DEFINE3(execve,
1753                 const char __user *, filename,
1754                 const char __user *const __user *, argv,
1755                 const char __user *const __user *, envp)
1756 {
1757         return do_execve(getname(filename), argv, envp);
1758 }
1759
1760 SYSCALL_DEFINE5(execveat,
1761                 int, fd, const char __user *, filename,
1762                 const char __user *const __user *, argv,
1763                 const char __user *const __user *, envp,
1764                 int, flags)
1765 {
1766         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1767
1768         return do_execveat(fd,
1769                            getname_flags(filename, lookup_flags, NULL),
1770                            argv, envp, flags);
1771 }
1772
1773 #ifdef CONFIG_COMPAT
1774 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
1775         const compat_uptr_t __user *, argv,
1776         const compat_uptr_t __user *, envp)
1777 {
1778         return compat_do_execve(getname(filename), argv, envp);
1779 }
1780
1781 COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
1782                        const char __user *, filename,
1783                        const compat_uptr_t __user *, argv,
1784                        const compat_uptr_t __user *, envp,
1785                        int,  flags)
1786 {
1787         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1788
1789         return compat_do_execveat(fd,
1790                                   getname_flags(filename, lookup_flags, NULL),
1791                                   argv, envp, flags);
1792 }
1793 #endif