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