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