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/stat.h>
  30 #include <linux/fcntl.h>
  31 #include <linux/swap.h>
  32 #include <linux/string.h>
  33 #include <linux/init.h>
  34 #include <linux/pagemap.h>
  35 #include <linux/perf_event.h>
  36 #include <linux/highmem.h>
  37 #include <linux/spinlock.h>
  38 #include <linux/key.h>
  39 #include <linux/personality.h>
  40 #include <linux/binfmts.h>
  41 #include <linux/utsname.h>
  42 #include <linux/pid_namespace.h>
  43 #include <linux/module.h>
  44 #include <linux/namei.h>
  45 #include <linux/mount.h>
  46 #include <linux/security.h>
  47 #include <linux/syscalls.h>
  48 #include <linux/tsacct_kern.h>
  49 #include <linux/cn_proc.h>
  50 #include <linux/audit.h>
  51 #include <linux/tracehook.h>
  52 #include <linux/kmod.h>
  53 #include <linux/fsnotify.h>
  54 #include <linux/fs_struct.h>
  55 #include <linux/pipe_fs_i.h>
  56 #include <linux/oom.h>
  57 #include <linux/compat.h>
  58
  59 #include <asm/uaccess.h>
  60 #include <asm/mmu_context.h>
  61 #include <asm/tlb.h>
  62
  63 #include <trace/events/task.h>
  64 #include "internal.h"
  65
  66 #include <trace/events/sched.h>
  67
  68 int suid_dumpable = 0;
  69
  70 static LIST_HEAD(formats);
  71 static DEFINE_RWLOCK(binfmt_lock);
  72
  73 void __register_binfmt(struct linux_binfmt * fmt, int insert)
  74 {
  75         BUG_ON(!fmt);
  76         write_lock(&binfmt_lock);
  77         insert ? list_add(&fmt->lh, &formats) :
  78                  list_add_tail(&fmt->lh, &formats);
  79         write_unlock(&binfmt_lock);
  80 }
  81
  82 EXPORT_SYMBOL(__register_binfmt);
  83
  84 void unregister_binfmt(struct linux_binfmt * fmt)
  85 {
  86         write_lock(&binfmt_lock);
  87         list_del(&fmt->lh);
  88         write_unlock(&binfmt_lock);
  89 }
  90
  91 EXPORT_SYMBOL(unregister_binfmt);
  92
  93 static inline void put_binfmt(struct linux_binfmt * fmt)
  94 {
  95         module_put(fmt->module);
  96 }
  97
  98 /*
  99  * Note that a shared library must be both readable and executable due to
 100  * security reasons.
 101  *
 102  * Also note that we take the address to load from from the file itself.
 103  */
 104 SYSCALL_DEFINE1(uselib, const char __user *, library)
 105 {
 106         struct file *file;
 107         char *tmp = getname(library);
 108         int error = PTR_ERR(tmp);
 109         static const struct open_flags uselib_flags = {
 110                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 111                 .acc_mode = MAY_READ | MAY_EXEC | MAY_OPEN,
 112                 .intent = LOOKUP_OPEN
 113         };
 114
 115         if (IS_ERR(tmp))
 116                 goto out;
 117
 118         file = do_filp_open(AT_FDCWD, tmp, &uselib_flags, LOOKUP_FOLLOW);
 119         putname(tmp);
 120         error = PTR_ERR(file);
 121         if (IS_ERR(file))
 122                 goto out;
 123
 124         error = -EINVAL;
 125         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
 126                 goto exit;
 127
 128         error = -EACCES;
 129         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 130                 goto exit;
 131
 132         fsnotify_open(file);
 133
 134         error = -ENOEXEC;
 135         if(file->f_op) {
 136                 struct linux_binfmt * fmt;
 137
 138                 read_lock(&binfmt_lock);
 139                 list_for_each_entry(fmt, &formats, lh) {
 140                         if (!fmt->load_shlib)
 141                                 continue;
 142                         if (!try_module_get(fmt->module))
 143                                 continue;
 144                         read_unlock(&binfmt_lock);
 145                         error = fmt->load_shlib(file);
 146                         read_lock(&binfmt_lock);
 147                         put_binfmt(fmt);
 148                         if (error != -ENOEXEC)
 149                                 break;
 150                 }
 151                 read_unlock(&binfmt_lock);
 152         }
 153 exit:
 154         fput(file);
 155 out:
 156         return error;
 157 }
 158
 159 #ifdef CONFIG_MMU
 160 /*
 161  * The nascent bprm->mm is not visible until exec_mmap() but it can
 162  * use a lot of memory, account these pages in current->mm temporary
 163  * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
 164  * change the counter back via acct_arg_size(0).
 165  */
 166 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 167 {
 168         struct mm_struct *mm = current->mm;
 169         long diff = (long)(pages - bprm->vma_pages);
 170
 171         if (!mm || !diff)
 172                 return;
 173
 174         bprm->vma_pages = pages;
 175         add_mm_counter(mm, MM_ANONPAGES, diff);
 176 }
 177
 178 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 179                 int write)
 180 {
 181         struct page *page;
 182         int ret;
 183
 184 #ifdef CONFIG_STACK_GROWSUP
 185         if (write) {
 186                 ret = expand_downwards(bprm->vma, pos);
 187                 if (ret < 0)
 188                         return NULL;
 189         }
 190 #endif
 191         ret = get_user_pages(current, bprm->mm, pos,
 192                         1, write, 1, &page, NULL);
 193         if (ret <= 0)
 194                 return NULL;
 195
 196         if (write) {
 197                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 198                 struct rlimit *rlim;
 199
 200                 acct_arg_size(bprm, size / PAGE_SIZE);
 201
 202                 /*
 203                  * We've historically supported up to 32 pages (ARG_MAX)
 204                  * of argument strings even with small stacks
 205                  */
 206                 if (size <= ARG_MAX)
 207                         return page;
 208
 209                 /*
 210                  * Limit to 1/4-th the stack size for the argv+env strings.
 211                  * This ensures that:
 212                  *  - the remaining binfmt code will not run out of stack space,
 213                  *  - the program will have a reasonable amount of stack left
 214                  *    to work from.
 215                  */
 216                 rlim = current->signal->rlim;
 217                 if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
 218                         put_page(page);
 219                         return NULL;
 220                 }
 221         }
 222
 223         return page;
 224 }
 225
 226 static void put_arg_page(struct page *page)
 227 {
 228         put_page(page);
 229 }
 230
 231 static void free_arg_page(struct linux_binprm *bprm, int i)
 232 {
 233 }
 234
 235 static void free_arg_pages(struct linux_binprm *bprm)
 236 {
 237 }
 238
 239 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 240                 struct page *page)
 241 {
 242         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 243 }
 244
 245 static int __bprm_mm_init(struct linux_binprm *bprm)
 246 {
 247         int err;
 248         struct vm_area_struct *vma = NULL;
 249         struct mm_struct *mm = bprm->mm;
 250
 251         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 252         if (!vma)
 253                 return -ENOMEM;
 254
 255         down_write(&mm->mmap_sem);
 256         vma->vm_mm = mm;
 257
 258         /*
 259          * Place the stack at the largest stack address the architecture
 260          * supports. Later, we'll move this to an appropriate place. We don't
 261          * use STACK_TOP because that can depend on attributes which aren't
 262          * configured yet.
 263          */
 264         BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 265         vma->vm_end = STACK_TOP_MAX;
 266         vma->vm_start = vma->vm_end - PAGE_SIZE;
 267         vma->vm_flags = VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 268         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 269         INIT_LIST_HEAD(&vma->anon_vma_chain);
 270
 271         err = insert_vm_struct(mm, vma);
 272         if (err)
 273                 goto err;
 274
 275         mm->stack_vm = mm->total_vm = 1;
 276         up_write(&mm->mmap_sem);
 277         bprm->p = vma->vm_end - sizeof(void *);
 278         return 0;
 279 err:
 280         up_write(&mm->mmap_sem);
 281         bprm->vma = NULL;
 282         kmem_cache_free(vm_area_cachep, vma);
 283         return err;
 284 }
 285
 286 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 287 {
 288         return len <= MAX_ARG_STRLEN;
 289 }
 290
 291 #else
 292
 293 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 294 {
 295 }
 296
 297 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 298                 int write)
 299 {
 300         struct page *page;
 301
 302         page = bprm->page[pos / PAGE_SIZE];
 303         if (!page && write) {
 304                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 305                 if (!page)
 306                         return NULL;
 307                 bprm->page[pos / PAGE_SIZE] = page;
 308         }
 309
 310         return page;
 311 }
 312
 313 static void put_arg_page(struct page *page)
 314 {
 315 }
 316
 317 static void free_arg_page(struct linux_binprm *bprm, int i)
 318 {
 319         if (bprm->page[i]) {
 320                 __free_page(bprm->page[i]);
 321                 bprm->page[i] = NULL;
 322         }
 323 }
 324
 325 static void free_arg_pages(struct linux_binprm *bprm)
 326 {
 327         int i;
 328
 329         for (i = 0; i < MAX_ARG_PAGES; i++)
 330                 free_arg_page(bprm, i);
 331 }
 332
 333 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 334                 struct page *page)
 335 {
 336 }
 337
 338 static int __bprm_mm_init(struct linux_binprm *bprm)
 339 {
 340         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 341         return 0;
 342 }
 343
 344 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 345 {
 346         return len <= bprm->p;
 347 }
 348
 349 #endif /* CONFIG_MMU */
 350
 351 /*
 352  * Create a new mm_struct and populate it with a temporary stack
 353  * vm_area_struct.  We don't have enough context at this point to set the stack
 354  * flags, permissions, and offset, so we use temporary values.  We'll update
 355  * them later in setup_arg_pages().
 356  */
 357 int bprm_mm_init(struct linux_binprm *bprm)
 358 {
 359         int err;
 360         struct mm_struct *mm = NULL;
 361
 362         bprm->mm = mm = mm_alloc();
 363         err = -ENOMEM;
 364         if (!mm)
 365                 goto err;
 366
 367         err = init_new_context(current, mm);
 368         if (err)
 369                 goto err;
 370
 371         err = __bprm_mm_init(bprm);
 372         if (err)
 373                 goto err;
 374
 375         return 0;
 376
 377 err:
 378         if (mm) {
 379                 bprm->mm = NULL;
 380                 mmdrop(mm);
 381         }
 382
 383         return err;
 384 }
 385
 386 struct user_arg_ptr {
 387 #ifdef CONFIG_COMPAT
 388         bool is_compat;
 389 #endif
 390         union {
 391                 const char __user *const __user *native;
 392 #ifdef CONFIG_COMPAT
 393                 const compat_uptr_t __user *compat;
 394 #endif
 395         } ptr;
 396 };
 397
 398 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
 399 {
 400         const char __user *native;
 401
 402 #ifdef CONFIG_COMPAT
 403         if (unlikely(argv.is_compat)) {
 404                 compat_uptr_t compat;
 405
 406                 if (get_user(compat, argv.ptr.compat + nr))
 407                         return ERR_PTR(-EFAULT);
 408
 409                 return compat_ptr(compat);
 410         }
 411 #endif
 412
 413         if (get_user(native, argv.ptr.native + nr))
 414                 return ERR_PTR(-EFAULT);
 415
 416         return native;
 417 }
 418
 419 /*
 420  * count() counts the number of strings in array ARGV.
 421  */
 422 static int count(struct user_arg_ptr argv, int max)
 423 {
 424         int i = 0;
 425
 426         if (argv.ptr.native != NULL) {
 427                 for (;;) {
 428                         const char __user *p = get_user_arg_ptr(argv, i);
 429
 430                         if (!p)
 431                                 break;
 432
 433                         if (IS_ERR(p))
 434                                 return -EFAULT;
 435
 436                         if (i++ >= max)
 437                                 return -E2BIG;
 438
 439                         if (fatal_signal_pending(current))
 440                                 return -ERESTARTNOHAND;
 441                         cond_resched();
 442                 }
 443         }
 444         return i;
 445 }
 446
 447 /*
 448  * 'copy_strings()' copies argument/environment strings from the old
 449  * processes's memory to the new process's stack.  The call to get_user_pages()
 450  * ensures the destination page is created and not swapped out.
 451  */
 452 static int copy_strings(int argc, struct user_arg_ptr argv,
 453                         struct linux_binprm *bprm)
 454 {
 455         struct page *kmapped_page = NULL;
 456         char *kaddr = NULL;
 457         unsigned long kpos = 0;
 458         int ret;
 459
 460         while (argc-- > 0) {
 461                 const char __user *str;
 462                 int len;
 463                 unsigned long pos;
 464
 465                 ret = -EFAULT;
 466                 str = get_user_arg_ptr(argv, argc);
 467                 if (IS_ERR(str))
 468                         goto out;
 469
 470                 len = strnlen_user(str, MAX_ARG_STRLEN);
 471                 if (!len)
 472                         goto out;
 473
 474                 ret = -E2BIG;
 475                 if (!valid_arg_len(bprm, len))
 476                         goto out;
 477
 478                 /* We're going to work our way backwords. */
 479                 pos = bprm->p;
 480                 str += len;
 481                 bprm->p -= len;
 482
 483                 while (len > 0) {
 484                         int offset, bytes_to_copy;
 485
 486                         if (fatal_signal_pending(current)) {
 487                                 ret = -ERESTARTNOHAND;
 488                                 goto out;
 489                         }
 490                         cond_resched();
 491
 492                         offset = pos % PAGE_SIZE;
 493                         if (offset == 0)
 494                                 offset = PAGE_SIZE;
 495
 496                         bytes_to_copy = offset;
 497                         if (bytes_to_copy > len)
 498                                 bytes_to_copy = len;
 499
 500                         offset -= bytes_to_copy;
 501                         pos -= bytes_to_copy;
 502                         str -= bytes_to_copy;
 503                         len -= bytes_to_copy;
 504
 505                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 506                                 struct page *page;
 507
 508                                 page = get_arg_page(bprm, pos, 1);
 509                                 if (!page) {
 510                                         ret = -E2BIG;
 511                                         goto out;
 512                                 }
 513
 514                                 if (kmapped_page) {
 515                                         flush_kernel_dcache_page(kmapped_page);
 516                                         kunmap(kmapped_page);
 517                                         put_arg_page(kmapped_page);
 518                                 }
 519                                 kmapped_page = page;
 520                                 kaddr = kmap(kmapped_page);
 521                                 kpos = pos & PAGE_MASK;
 522                                 flush_arg_page(bprm, kpos, kmapped_page);
 523                         }
 524                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 525                                 ret = -EFAULT;
 526                                 goto out;
 527                         }
 528                 }
 529         }
 530         ret = 0;
 531 out:
 532         if (kmapped_page) {
 533                 flush_kernel_dcache_page(kmapped_page);
 534                 kunmap(kmapped_page);
 535                 put_arg_page(kmapped_page);
 536         }
 537         return ret;
 538 }
 539
 540 /*
 541  * Like copy_strings, but get argv and its values from kernel memory.
 542  */
 543 int copy_strings_kernel(int argc, const char *const *__argv,
 544                         struct linux_binprm *bprm)
 545 {
 546         int r;
 547         mm_segment_t oldfs = get_fs();
 548         struct user_arg_ptr argv = {
 549                 .ptr.native = (const char __user *const  __user *)__argv,
 550         };
 551
 552         set_fs(KERNEL_DS);
 553         r = copy_strings(argc, argv, bprm);
 554         set_fs(oldfs);
 555
 556         return r;
 557 }
 558 EXPORT_SYMBOL(copy_strings_kernel);
 559
 560 #ifdef CONFIG_MMU
 561
 562 /*
 563  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 564  * the binfmt code determines where the new stack should reside, we shift it to
 565  * its final location.  The process proceeds as follows:
 566  *
 567  * 1) Use shift to calculate the new vma endpoints.
 568  * 2) Extend vma to cover both the old and new ranges.  This ensures the
 569  *    arguments passed to subsequent functions are consistent.
 570  * 3) Move vma's page tables to the new range.
 571  * 4) Free up any cleared pgd range.
 572  * 5) Shrink the vma to cover only the new range.
 573  */
 574 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 575 {
 576         struct mm_struct *mm = vma->vm_mm;
 577         unsigned long old_start = vma->vm_start;
 578         unsigned long old_end = vma->vm_end;
 579         unsigned long length = old_end - old_start;
 580         unsigned long new_start = old_start - shift;
 581         unsigned long new_end = old_end - shift;
 582         struct mmu_gather tlb;
 583
 584         BUG_ON(new_start > new_end);
 585
 586         /*
 587          * ensure there are no vmas between where we want to go
 588          * and where we are
 589          */
 590         if (vma != find_vma(mm, new_start))
 591                 return -EFAULT;
 592
 593         /*
 594          * cover the whole range: [new_start, old_end)
 595          */
 596         if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
 597                 return -ENOMEM;
 598
 599         /*
 600          * move the page tables downwards, on failure we rely on
 601          * process cleanup to remove whatever mess we made.
 602          */
 603         if (length != move_page_tables(vma, old_start,
 604                                        vma, new_start, length, false))
 605                 return -ENOMEM;
 606
 607         lru_add_drain();
 608         tlb_gather_mmu(&tlb, mm, 0);
 609         if (new_end > old_start) {
 610                 /*
 611                  * when the old and new regions overlap clear from new_end.
 612                  */
 613                 free_pgd_range(&tlb, new_end, old_end, new_end,
 614                         vma->vm_next ? vma->vm_next->vm_start : 0);
 615         } else {
 616                 /*
 617                  * otherwise, clean from old_start; this is done to not touch
 618                  * the address space in [new_end, old_start) some architectures
 619                  * have constraints on va-space that make this illegal (IA64) -
 620                  * for the others its just a little faster.
 621                  */
 622                 free_pgd_range(&tlb, old_start, old_end, new_end,
 623                         vma->vm_next ? vma->vm_next->vm_start : 0);
 624         }
 625         tlb_finish_mmu(&tlb, new_end, old_end);
 626
 627         /*
 628          * Shrink the vma to just the new range.  Always succeeds.
 629          */
 630         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 631
 632         return 0;
 633 }
 634
 635 /*
 636  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 637  * the stack is optionally relocated, and some extra space is added.
 638  */
 639 int setup_arg_pages(struct linux_binprm *bprm,
 640                     unsigned long stack_top,
 641                     int executable_stack)
 642 {
 643         unsigned long ret;
 644         unsigned long stack_shift;
 645         struct mm_struct *mm = current->mm;
 646         struct vm_area_struct *vma = bprm->vma;
 647         struct vm_area_struct *prev = NULL;
 648         unsigned long vm_flags;
 649         unsigned long stack_base;
 650         unsigned long stack_size;
 651         unsigned long stack_expand;
 652         unsigned long rlim_stack;
 653
 654 #ifdef CONFIG_STACK_GROWSUP
 655         /* Limit stack size to 1GB */
 656         stack_base = rlimit_max(RLIMIT_STACK);
 657         if (stack_base > (1 << 30))
 658                 stack_base = 1 << 30;
 659
 660         /* Make sure we didn't let the argument array grow too large. */
 661         if (vma->vm_end - vma->vm_start > stack_base)
 662                 return -ENOMEM;
 663
 664         stack_base = PAGE_ALIGN(stack_top - stack_base);
 665
 666         stack_shift = vma->vm_start - stack_base;
 667         mm->arg_start = bprm->p - stack_shift;
 668         bprm->p = vma->vm_end - stack_shift;
 669 #else
 670         stack_top = arch_align_stack(stack_top);
 671         stack_top = PAGE_ALIGN(stack_top);
 672
 673         if (unlikely(stack_top < mmap_min_addr) ||
 674             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 675                 return -ENOMEM;
 676
 677         stack_shift = vma->vm_end - stack_top;
 678
 679         bprm->p -= stack_shift;
 680         mm->arg_start = bprm->p;
 681 #endif
 682
 683         if (bprm->loader)
 684                 bprm->loader -= stack_shift;
 685         bprm->exec -= stack_shift;
 686
 687         down_write(&mm->mmap_sem);
 688         vm_flags = VM_STACK_FLAGS;
 689
 690         /*
 691          * Adjust stack execute permissions; explicitly enable for
 692          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 693          * (arch default) otherwise.
 694          */
 695         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 696                 vm_flags |= VM_EXEC;
 697         else if (executable_stack == EXSTACK_DISABLE_X)
 698                 vm_flags &= ~VM_EXEC;
 699         vm_flags |= mm->def_flags;
 700         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 701
 702         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 703                         vm_flags);
 704         if (ret)
 705                 goto out_unlock;
 706         BUG_ON(prev != vma);
 707
 708         /* Move stack pages down in memory. */
 709         if (stack_shift) {
 710                 ret = shift_arg_pages(vma, stack_shift);
 711                 if (ret)
 712                         goto out_unlock;
 713         }
 714
 715         /* mprotect_fixup is overkill to remove the temporary stack flags */
 716         vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
 717
 718         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
 719         stack_size = vma->vm_end - vma->vm_start;
 720         /*
 721          * Align this down to a page boundary as expand_stack
 722          * will align it up.
 723          */
 724         rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 725 #ifdef CONFIG_STACK_GROWSUP
 726         if (stack_size + stack_expand > rlim_stack)
 727                 stack_base = vma->vm_start + rlim_stack;
 728         else
 729                 stack_base = vma->vm_end + stack_expand;
 730 #else
 731         if (stack_size + stack_expand > rlim_stack)
 732                 stack_base = vma->vm_end - rlim_stack;
 733         else
 734                 stack_base = vma->vm_start - stack_expand;
 735 #endif
 736         current->mm->start_stack = bprm->p;
 737         ret = expand_stack(vma, stack_base);
 738         if (ret)
 739                 ret = -EFAULT;
 740
 741 out_unlock:
 742         up_write(&mm->mmap_sem);
 743         return ret;
 744 }
 745 EXPORT_SYMBOL(setup_arg_pages);
 746
 747 #endif /* CONFIG_MMU */
 748
 749 struct file *open_exec(const char *name)
 750 {
 751         struct file *file;
 752         int err;
 753         static const struct open_flags open_exec_flags = {
 754                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 755                 .acc_mode = MAY_EXEC | MAY_OPEN,
 756                 .intent = LOOKUP_OPEN
 757         };
 758
 759         file = do_filp_open(AT_FDCWD, name, &open_exec_flags, LOOKUP_FOLLOW);
 760         if (IS_ERR(file))
 761                 goto out;
 762
 763         err = -EACCES;
 764         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
 765                 goto exit;
 766
 767         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 768                 goto exit;
 769
 770         fsnotify_open(file);
 771
 772         err = deny_write_access(file);
 773         if (err)
 774                 goto exit;
 775
 776 out:
 777         return file;
 778
 779 exit:
 780         fput(file);
 781         return ERR_PTR(err);
 782 }
 783 EXPORT_SYMBOL(open_exec);
 784
 785 int kernel_read(struct file *file, loff_t offset,
 786                 char *addr, unsigned long count)
 787 {
 788         mm_segment_t old_fs;
 789         loff_t pos = offset;
 790         int result;
 791
 792         old_fs = get_fs();
 793         set_fs(get_ds());
 794         /* The cast to a user pointer is valid due to the set_fs() */
 795         result = vfs_read(file, (void __user *)addr, count, &pos);
 796         set_fs(old_fs);
 797         return result;
 798 }
 799
 800 EXPORT_SYMBOL(kernel_read);
 801
 802 static int exec_mmap(struct mm_struct *mm)
 803 {
 804         struct task_struct *tsk;
 805         struct mm_struct * old_mm, *active_mm;
 806
 807         /* Notify parent that we're no longer interested in the old VM */
 808         tsk = current;
 809         old_mm = current->mm;
 810         mm_release(tsk, old_mm);
 811
 812         if (old_mm) {
 813                 sync_mm_rss(old_mm);
 814                 /*
 815                  * Make sure that if there is a core dump in progress
 816                  * for the old mm, we get out and die instead of going
 817                  * through with the exec.  We must hold mmap_sem around
 818                  * checking core_state and changing tsk->mm.
 819                  */
 820                 down_read(&old_mm->mmap_sem);
 821                 if (unlikely(old_mm->core_state)) {
 822                         up_read(&old_mm->mmap_sem);
 823                         return -EINTR;
 824                 }
 825         }
 826         task_lock(tsk);
 827         active_mm = tsk->active_mm;
 828         tsk->mm = mm;
 829         tsk->active_mm = mm;
 830         activate_mm(active_mm, mm);
 831         task_unlock(tsk);
 832         arch_pick_mmap_layout(mm);
 833         if (old_mm) {
 834                 up_read(&old_mm->mmap_sem);
 835                 BUG_ON(active_mm != old_mm);
 836                 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
 837                 mm_update_next_owner(old_mm);
 838                 mmput(old_mm);
 839                 return 0;
 840         }
 841         mmdrop(active_mm);
 842         return 0;
 843 }
 844
 845 /*
 846  * This function makes sure the current process has its own signal table,
 847  * so that flush_signal_handlers can later reset the handlers without
 848  * disturbing other processes.  (Other processes might share the signal
 849  * table via the CLONE_SIGHAND option to clone().)
 850  */
 851 static int de_thread(struct task_struct *tsk)
 852 {
 853         struct signal_struct *sig = tsk->signal;
 854         struct sighand_struct *oldsighand = tsk->sighand;
 855         spinlock_t *lock = &oldsighand->siglock;
 856
 857         if (thread_group_empty(tsk))
 858                 goto no_thread_group;
 859
 860         /*
 861          * Kill all other threads in the thread group.
 862          */
 863         spin_lock_irq(lock);
 864         if (signal_group_exit(sig)) {
 865                 /*
 866                  * Another group action in progress, just
 867                  * return so that the signal is processed.
 868                  */
 869                 spin_unlock_irq(lock);
 870                 return -EAGAIN;
 871         }
 872
 873         sig->group_exit_task = tsk;
 874         sig->notify_count = zap_other_threads(tsk);
 875         if (!thread_group_leader(tsk))
 876                 sig->notify_count--;
 877
 878         while (sig->notify_count) {
 879                 __set_current_state(TASK_UNINTERRUPTIBLE);
 880                 spin_unlock_irq(lock);
 881                 schedule();
 882                 spin_lock_irq(lock);
 883         }
 884         spin_unlock_irq(lock);
 885
 886         /*
 887          * At this point all other threads have exited, all we have to
 888          * do is to wait for the thread group leader to become inactive,
 889          * and to assume its PID:
 890          */
 891         if (!thread_group_leader(tsk)) {
 892                 struct task_struct *leader = tsk->group_leader;
 893
 894                 sig->notify_count = -1; /* for exit_notify() */
 895                 for (;;) {
 896                         write_lock_irq(&tasklist_lock);
 897                         if (likely(leader->exit_state))
 898                                 break;
 899                         __set_current_state(TASK_UNINTERRUPTIBLE);
 900                         write_unlock_irq(&tasklist_lock);
 901                         schedule();
 902                 }
 903
 904                 /*
 905                  * The only record we have of the real-time age of a
 906                  * process, regardless of execs it's done, is start_time.
 907                  * All the past CPU time is accumulated in signal_struct
 908                  * from sister threads now dead.  But in this non-leader
 909                  * exec, nothing survives from the original leader thread,
 910                  * whose birth marks the true age of this process now.
 911                  * When we take on its identity by switching to its PID, we
 912                  * also take its birthdate (always earlier than our own).
 913                  */
 914                 tsk->start_time = leader->start_time;
 915
 916                 BUG_ON(!same_thread_group(leader, tsk));
 917                 BUG_ON(has_group_leader_pid(tsk));
 918                 /*
 919                  * An exec() starts a new thread group with the
 920                  * TGID of the previous thread group. Rehash the
 921                  * two threads with a switched PID, and release
 922                  * the former thread group leader:
 923                  */
 924
 925                 /* Become a process group leader with the old leader's pid.
 926                  * The old leader becomes a thread of the this thread group.
 927                  * Note: The old leader also uses this pid until release_task
 928                  *       is called.  Odd but simple and correct.
 929                  */
 930                 detach_pid(tsk, PIDTYPE_PID);
 931                 tsk->pid = leader->pid;
 932                 attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
 933                 transfer_pid(leader, tsk, PIDTYPE_PGID);
 934                 transfer_pid(leader, tsk, PIDTYPE_SID);
 935
 936                 list_replace_rcu(&leader->tasks, &tsk->tasks);
 937                 list_replace_init(&leader->sibling, &tsk->sibling);
 938
 939                 tsk->group_leader = tsk;
 940                 leader->group_leader = tsk;
 941
 942                 tsk->exit_signal = SIGCHLD;
 943                 leader->exit_signal = -1;
 944
 945                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 946                 leader->exit_state = EXIT_DEAD;
 947
 948                 /*
 949                  * We are going to release_task()->ptrace_unlink() silently,
 950                  * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
 951                  * the tracer wont't block again waiting for this thread.
 952                  */
 953                 if (unlikely(leader->ptrace))
 954                         __wake_up_parent(leader, leader->parent);
 955                 write_unlock_irq(&tasklist_lock);
 956
 957                 release_task(leader);
 958         }
 959
 960         sig->group_exit_task = NULL;
 961         sig->notify_count = 0;
 962
 963 no_thread_group:
 964         /* we have changed execution domain */
 965         tsk->exit_signal = SIGCHLD;
 966
 967         exit_itimers(sig);
 968         flush_itimer_signals();
 969
 970         if (atomic_read(&oldsighand->count) != 1) {
 971                 struct sighand_struct *newsighand;
 972                 /*
 973                  * This ->sighand is shared with the CLONE_SIGHAND
 974                  * but not CLONE_THREAD task, switch to the new one.
 975                  */
 976                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 977                 if (!newsighand)
 978                         return -ENOMEM;
 979
 980                 atomic_set(&newsighand->count, 1);
 981                 memcpy(newsighand->action, oldsighand->action,
 982                        sizeof(newsighand->action));
 983
 984                 write_lock_irq(&tasklist_lock);
 985                 spin_lock(&oldsighand->siglock);
 986                 rcu_assign_pointer(tsk->sighand, newsighand);
 987                 spin_unlock(&oldsighand->siglock);
 988                 write_unlock_irq(&tasklist_lock);
 989
 990                 __cleanup_sighand(oldsighand);
 991         }
 992
 993         BUG_ON(!thread_group_leader(tsk));
 994         return 0;
 995 }
 996
 997 /*
 998  * These functions flushes out all traces of the currently running executable
 999  * so that a new one can be started
1000  */
1001 static void flush_old_files(struct files_struct * files)
1002 {
1003         long j = -1;
1004         struct fdtable *fdt;
1005
1006         spin_lock(&files->file_lock);
1007         for (;;) {
1008                 unsigned long set, i;
1009
1010                 j++;
1011                 i = j * BITS_PER_LONG;
1012                 fdt = files_fdtable(files);
1013                 if (i >= fdt->max_fds)
1014                         break;
1015                 set = fdt->close_on_exec[j];
1016                 if (!set)
1017                         continue;
1018                 fdt->close_on_exec[j] = 0;
1019                 spin_unlock(&files->file_lock);
1020                 for ( ; set ; i++,set >>= 1) {
1021                         if (set & 1) {
1022                                 sys_close(i);
1023                         }
1024                 }
1025                 spin_lock(&files->file_lock);
1026
1027         }
1028         spin_unlock(&files->file_lock);
1029 }
1030
1031 char *get_task_comm(char *buf, struct task_struct *tsk)
1032 {
1033         /* buf must be at least sizeof(tsk->comm) in size */
1034         task_lock(tsk);
1035         strncpy(buf, tsk->comm, sizeof(tsk->comm));
1036         task_unlock(tsk);
1037         return buf;
1038 }
1039 EXPORT_SYMBOL_GPL(get_task_comm);
1040
1041 void set_task_comm(struct task_struct *tsk, char *buf)
1042 {
1043         task_lock(tsk);
1044
1045         trace_task_rename(tsk, buf);
1046
1047         /*
1048          * Threads may access current->comm without holding
1049          * the task lock, so write the string carefully.
1050          * Readers without a lock may see incomplete new
1051          * names but are safe from non-terminating string reads.
1052          */
1053         memset(tsk->comm, 0, TASK_COMM_LEN);
1054         wmb();
1055         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1056         task_unlock(tsk);
1057         perf_event_comm(tsk);
1058 }
1059
1060 static void filename_to_taskname(char *tcomm, const char *fn, unsigned int len)
1061 {
1062         int i, ch;
1063
1064         /* Copies the binary name from after last slash */
1065         for (i = 0; (ch = *(fn++)) != '\0';) {
1066                 if (ch == '/')
1067                         i = 0; /* overwrite what we wrote */
1068                 else
1069                         if (i < len - 1)
1070                                 tcomm[i++] = ch;
1071         }
1072         tcomm[i] = '\0';
1073 }
1074
1075 int flush_old_exec(struct linux_binprm * bprm)
1076 {
1077         int retval;
1078
1079         /*
1080          * Make sure we have a private signal table and that
1081          * we are unassociated from the previous thread group.
1082          */
1083         retval = de_thread(current);
1084         if (retval)
1085                 goto out;
1086
1087         set_mm_exe_file(bprm->mm, bprm->file);
1088
1089         filename_to_taskname(bprm->tcomm, bprm->filename, sizeof(bprm->tcomm));
1090         /*
1091          * Release all of the old mmap stuff
1092          */
1093         acct_arg_size(bprm, 0);
1094         retval = exec_mmap(bprm->mm);
1095         if (retval)
1096                 goto out;
1097
1098         bprm->mm = NULL;                /* We're using it now */
1099
1100         set_fs(USER_DS);
1101         current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD);
1102         flush_thread();
1103         current->personality &= ~bprm->per_clear;
1104
1105         return 0;
1106
1107 out:
1108         return retval;
1109 }
1110 EXPORT_SYMBOL(flush_old_exec);
1111
1112 void would_dump(struct linux_binprm *bprm, struct file *file)
1113 {
1114         if (inode_permission(file->f_path.dentry->d_inode, MAY_READ) < 0)
1115                 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1116 }
1117 EXPORT_SYMBOL(would_dump);
1118
1119 void setup_new_exec(struct linux_binprm * bprm)
1120 {
1121         arch_pick_mmap_layout(current->mm);
1122
1123         /* This is the point of no return */
1124         current->sas_ss_sp = current->sas_ss_size = 0;
1125
1126         if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid()))
1127                 set_dumpable(current->mm, 1);
1128         else
1129                 set_dumpable(current->mm, suid_dumpable);
1130
1131         set_task_comm(current, bprm->tcomm);
1132
1133         /* Set the new mm task size. We have to do that late because it may
1134          * depend on TIF_32BIT which is only updated in flush_thread() on
1135          * some architectures like powerpc
1136          */
1137         current->mm->task_size = TASK_SIZE;
1138
1139         /* install the new credentials */
1140         if (!uid_eq(bprm->cred->uid, current_euid()) ||
1141             !gid_eq(bprm->cred->gid, current_egid())) {
1142                 current->pdeath_signal = 0;
1143         } else {
1144                 would_dump(bprm, bprm->file);
1145                 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
1146                         set_dumpable(current->mm, suid_dumpable);
1147         }
1148
1149         /*
1150          * Flush performance counters when crossing a
1151          * security domain:
1152          */
1153         if (!get_dumpable(current->mm))
1154                 perf_event_exit_task(current);
1155
1156         /* An exec changes our domain. We are no longer part of the thread
1157            group */
1158
1159         current->self_exec_id++;
1160
1161         flush_signal_handlers(current, 0);
1162         flush_old_files(current->files);
1163 }
1164 EXPORT_SYMBOL(setup_new_exec);
1165
1166 /*
1167  * Prepare credentials and lock ->cred_guard_mutex.
1168  * install_exec_creds() commits the new creds and drops the lock.
1169  * Or, if exec fails before, free_bprm() should release ->cred and
1170  * and unlock.
1171  */
1172 int prepare_bprm_creds(struct linux_binprm *bprm)
1173 {
1174         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1175                 return -ERESTARTNOINTR;
1176
1177         bprm->cred = prepare_exec_creds();
1178         if (likely(bprm->cred))
1179                 return 0;
1180
1181         mutex_unlock(&current->signal->cred_guard_mutex);
1182         return -ENOMEM;
1183 }
1184
1185 void free_bprm(struct linux_binprm *bprm)
1186 {
1187         free_arg_pages(bprm);
1188         if (bprm->cred) {
1189                 mutex_unlock(&current->signal->cred_guard_mutex);
1190                 abort_creds(bprm->cred);
1191         }
1192         kfree(bprm);
1193 }
1194
1195 /*
1196  * install the new credentials for this executable
1197  */
1198 void install_exec_creds(struct linux_binprm *bprm)
1199 {
1200         security_bprm_committing_creds(bprm);
1201
1202         commit_creds(bprm->cred);
1203         bprm->cred = NULL;
1204         /*
1205          * cred_guard_mutex must be held at least to this point to prevent
1206          * ptrace_attach() from altering our determination of the task's
1207          * credentials; any time after this it may be unlocked.
1208          */
1209         security_bprm_committed_creds(bprm);
1210         mutex_unlock(&current->signal->cred_guard_mutex);
1211 }
1212 EXPORT_SYMBOL(install_exec_creds);
1213
1214 /*
1215  * determine how safe it is to execute the proposed program
1216  * - the caller must hold ->cred_guard_mutex to protect against
1217  *   PTRACE_ATTACH
1218  */
1219 static int check_unsafe_exec(struct linux_binprm *bprm)
1220 {
1221         struct task_struct *p = current, *t;
1222         unsigned n_fs;
1223         int res = 0;
1224
1225         if (p->ptrace) {
1226                 if (p->ptrace & PT_PTRACE_CAP)
1227                         bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP;
1228                 else
1229                         bprm->unsafe |= LSM_UNSAFE_PTRACE;
1230         }
1231
1232         /*
1233          * This isn't strictly necessary, but it makes it harder for LSMs to
1234          * mess up.
1235          */
1236         if (current->no_new_privs)
1237                 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1238
1239         n_fs = 1;
1240         spin_lock(&p->fs->lock);
1241         rcu_read_lock();
1242         for (t = next_thread(p); t != p; t = next_thread(t)) {
1243                 if (t->fs == p->fs)
1244                         n_fs++;
1245         }
1246         rcu_read_unlock();
1247
1248         if (p->fs->users > n_fs) {
1249                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1250         } else {
1251                 res = -EAGAIN;
1252                 if (!p->fs->in_exec) {
1253                         p->fs->in_exec = 1;
1254                         res = 1;
1255                 }
1256         }
1257         spin_unlock(&p->fs->lock);
1258
1259         return res;
1260 }
1261
1262 /*
1263  * Fill the binprm structure from the inode.
1264  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1265  *
1266  * This may be called multiple times for binary chains (scripts for example).
1267  */
1268 int prepare_binprm(struct linux_binprm *bprm)
1269 {
1270         umode_t mode;
1271         struct inode * inode = bprm->file->f_path.dentry->d_inode;
1272         int retval;
1273
1274         mode = inode->i_mode;
1275         if (bprm->file->f_op == NULL)
1276                 return -EACCES;
1277
1278         /* clear any previous set[ug]id data from a previous binary */
1279         bprm->cred->euid = current_euid();
1280         bprm->cred->egid = current_egid();
1281
1282         if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) &&
1283             !current->no_new_privs) {
1284                 /* Set-uid? */
1285                 if (mode & S_ISUID) {
1286                         if (!kuid_has_mapping(bprm->cred->user_ns, inode->i_uid))
1287                                 return -EPERM;
1288                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1289                         bprm->cred->euid = inode->i_uid;
1290
1291                 }
1292
1293                 /* Set-gid? */
1294                 /*
1295                  * If setgid is set but no group execute bit then this
1296                  * is a candidate for mandatory locking, not a setgid
1297                  * executable.
1298                  */
1299                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1300                         if (!kgid_has_mapping(bprm->cred->user_ns, inode->i_gid))
1301                                 return -EPERM;
1302                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1303                         bprm->cred->egid = inode->i_gid;
1304                 }
1305         }
1306
1307         /* fill in binprm security blob */
1308         retval = security_bprm_set_creds(bprm);
1309         if (retval)
1310                 return retval;
1311         bprm->cred_prepared = 1;
1312
1313         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1314         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1315 }
1316
1317 EXPORT_SYMBOL(prepare_binprm);
1318
1319 /*
1320  * Arguments are '\0' separated strings found at the location bprm->p
1321  * points to; chop off the first by relocating brpm->p to right after
1322  * the first '\0' encountered.
1323  */
1324 int remove_arg_zero(struct linux_binprm *bprm)
1325 {
1326         int ret = 0;
1327         unsigned long offset;
1328         char *kaddr;
1329         struct page *page;
1330
1331         if (!bprm->argc)
1332                 return 0;
1333
1334         do {
1335                 offset = bprm->p & ~PAGE_MASK;
1336                 page = get_arg_page(bprm, bprm->p, 0);
1337                 if (!page) {
1338                         ret = -EFAULT;
1339                         goto out;
1340                 }
1341                 kaddr = kmap_atomic(page);
1342
1343                 for (; offset < PAGE_SIZE && kaddr[offset];
1344                                 offset++, bprm->p++)
1345                         ;
1346
1347                 kunmap_atomic(kaddr);
1348                 put_arg_page(page);
1349
1350                 if (offset == PAGE_SIZE)
1351                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1352         } while (offset == PAGE_SIZE);
1353
1354         bprm->p++;
1355         bprm->argc--;
1356         ret = 0;
1357
1358 out:
1359         return ret;
1360 }
1361 EXPORT_SYMBOL(remove_arg_zero);
1362
1363 /*
1364  * cycle the list of binary formats handler, until one recognizes the image
1365  */
1366 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1367 {
1368         unsigned int depth = bprm->recursion_depth;
1369         int try,retval;
1370         struct linux_binfmt *fmt;
1371         pid_t old_pid, old_vpid;
1372
1373         retval = security_bprm_check(bprm);
1374         if (retval)
1375                 return retval;
1376
1377         retval = audit_bprm(bprm);
1378         if (retval)
1379                 return retval;
1380
1381         /* Need to fetch pid before load_binary changes it */
1382         old_pid = current->pid;
1383         rcu_read_lock();
1384         old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1385         rcu_read_unlock();
1386
1387         retval = -ENOENT;
1388         for (try=0; try<2; try++) {
1389                 read_lock(&binfmt_lock);
1390                 list_for_each_entry(fmt, &formats, lh) {
1391                         int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1392                         if (!fn)
1393                                 continue;
1394                         if (!try_module_get(fmt->module))
1395                                 continue;
1396                         read_unlock(&binfmt_lock);
1397                         retval = fn(bprm, regs);
1398                         /*
1399                          * Restore the depth counter to its starting value
1400                          * in this call, so we don't have to rely on every
1401                          * load_binary function to restore it on return.
1402                          */
1403                         bprm->recursion_depth = depth;
1404                         if (retval >= 0) {
1405                                 if (depth == 0) {
1406                                         trace_sched_process_exec(current, old_pid, bprm);
1407                                         ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1408                                 }
1409                                 put_binfmt(fmt);
1410                                 allow_write_access(bprm->file);
1411                                 if (bprm->file)
1412                                         fput(bprm->file);
1413                                 bprm->file = NULL;
1414                                 current->did_exec = 1;
1415                                 proc_exec_connector(current);
1416                                 return retval;
1417                         }
1418                         read_lock(&binfmt_lock);
1419                         put_binfmt(fmt);
1420                         if (retval != -ENOEXEC || bprm->mm == NULL)
1421                                 break;
1422                         if (!bprm->file) {
1423                                 read_unlock(&binfmt_lock);
1424                                 return retval;
1425                         }
1426                 }
1427                 read_unlock(&binfmt_lock);
1428 #ifdef CONFIG_MODULES
1429                 if (retval != -ENOEXEC || bprm->mm == NULL) {
1430                         break;
1431                 } else {
1432 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1433                         if (printable(bprm->buf[0]) &&
1434                             printable(bprm->buf[1]) &&
1435                             printable(bprm->buf[2]) &&
1436                             printable(bprm->buf[3]))
1437                                 break; /* -ENOEXEC */
1438                         if (try)
1439                                 break; /* -ENOEXEC */
1440                         request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1441                 }
1442 #else
1443                 break;
1444 #endif
1445         }
1446         return retval;
1447 }
1448
1449 EXPORT_SYMBOL(search_binary_handler);
1450
1451 /*
1452  * sys_execve() executes a new program.
1453  */
1454 static int do_execve_common(const char *filename,
1455                                 struct user_arg_ptr argv,
1456                                 struct user_arg_ptr envp,
1457                                 struct pt_regs *regs)
1458 {
1459         struct linux_binprm *bprm;
1460         struct file *file;
1461         struct files_struct *displaced;
1462         bool clear_in_exec;
1463         int retval;
1464         const struct cred *cred = current_cred();
1465
1466         /*
1467          * We move the actual failure in case of RLIMIT_NPROC excess from
1468          * set*uid() to execve() because too many poorly written programs
1469          * don't check setuid() return code.  Here we additionally recheck
1470          * whether NPROC limit is still exceeded.
1471          */
1472         if ((current->flags & PF_NPROC_EXCEEDED) &&
1473             atomic_read(&cred->user->processes) > rlimit(RLIMIT_NPROC)) {
1474                 retval = -EAGAIN;
1475                 goto out_ret;
1476         }
1477
1478         /* We're below the limit (still or again), so we don't want to make
1479          * further execve() calls fail. */
1480         current->flags &= ~PF_NPROC_EXCEEDED;
1481
1482         retval = unshare_files(&displaced);
1483         if (retval)
1484                 goto out_ret;
1485
1486         retval = -ENOMEM;
1487         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1488         if (!bprm)
1489                 goto out_files;
1490
1491         retval = prepare_bprm_creds(bprm);
1492         if (retval)
1493                 goto out_free;
1494
1495         retval = check_unsafe_exec(bprm);
1496         if (retval < 0)
1497                 goto out_free;
1498         clear_in_exec = retval;
1499         current->in_execve = 1;
1500
1501         file = open_exec(filename);
1502         retval = PTR_ERR(file);
1503         if (IS_ERR(file))
1504                 goto out_unmark;
1505
1506         sched_exec();
1507
1508         bprm->file = file;
1509         bprm->filename = filename;
1510         bprm->interp = filename;
1511
1512         retval = bprm_mm_init(bprm);
1513         if (retval)
1514                 goto out_file;
1515
1516         bprm->argc = count(argv, MAX_ARG_STRINGS);
1517         if ((retval = bprm->argc) < 0)
1518                 goto out;
1519
1520         bprm->envc = count(envp, MAX_ARG_STRINGS);
1521         if ((retval = bprm->envc) < 0)
1522                 goto out;
1523
1524         retval = prepare_binprm(bprm);
1525         if (retval < 0)
1526                 goto out;
1527
1528         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1529         if (retval < 0)
1530                 goto out;
1531
1532         bprm->exec = bprm->p;
1533         retval = copy_strings(bprm->envc, envp, bprm);
1534         if (retval < 0)
1535                 goto out;
1536
1537         retval = copy_strings(bprm->argc, argv, bprm);
1538         if (retval < 0)
1539                 goto out;
1540
1541         retval = search_binary_handler(bprm,regs);
1542         if (retval < 0)
1543                 goto out;
1544
1545         /* execve succeeded */
1546         current->fs->in_exec = 0;
1547         current->in_execve = 0;
1548         acct_update_integrals(current);
1549         free_bprm(bprm);
1550         if (displaced)
1551                 put_files_struct(displaced);
1552         return retval;
1553
1554 out:
1555         if (bprm->mm) {
1556                 acct_arg_size(bprm, 0);
1557                 mmput(bprm->mm);
1558         }
1559
1560 out_file:
1561         if (bprm->file) {
1562                 allow_write_access(bprm->file);
1563                 fput(bprm->file);
1564         }
1565
1566 out_unmark:
1567         if (clear_in_exec)
1568                 current->fs->in_exec = 0;
1569         current->in_execve = 0;
1570
1571 out_free:
1572         free_bprm(bprm);
1573
1574 out_files:
1575         if (displaced)
1576                 reset_files_struct(displaced);
1577 out_ret:
1578         return retval;
1579 }
1580
1581 int do_execve(const char *filename,
1582         const char __user *const __user *__argv,
1583         const char __user *const __user *__envp,
1584         struct pt_regs *regs)
1585 {
1586         struct user_arg_ptr argv = { .ptr.native = __argv };
1587         struct user_arg_ptr envp = { .ptr.native = __envp };
1588         return do_execve_common(filename, argv, envp, regs);
1589 }
1590
1591 #ifdef CONFIG_COMPAT
1592 int compat_do_execve(const char *filename,
1593         const compat_uptr_t __user *__argv,
1594         const compat_uptr_t __user *__envp,
1595         struct pt_regs *regs)
1596 {
1597         struct user_arg_ptr argv = {
1598                 .is_compat = true,
1599                 .ptr.compat = __argv,
1600         };
1601         struct user_arg_ptr envp = {
1602                 .is_compat = true,
1603                 .ptr.compat = __envp,
1604         };
1605         return do_execve_common(filename, argv, envp, regs);
1606 }
1607 #endif
1608
1609 void set_binfmt(struct linux_binfmt *new)
1610 {
1611         struct mm_struct *mm = current->mm;
1612
1613         if (mm->binfmt)
1614                 module_put(mm->binfmt->module);
1615
1616         mm->binfmt = new;
1617         if (new)
1618                 __module_get(new->module);
1619 }
1620
1621 EXPORT_SYMBOL(set_binfmt);
1622
1623 /*
1624  * set_dumpable converts traditional three-value dumpable to two flags and
1625  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1626  * these bits are not changed atomically.  So get_dumpable can observe the
1627  * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1628  * return either old dumpable or new one by paying attention to the order of
1629  * modifying the bits.
1630  *
1631  * dumpable |   mm->flags (binary)
1632  * old  new | initial interim  final
1633  * ---------+-----------------------
1634  *  0    1  |   00      01      01
1635  *  0    2  |   00      10(*)   11
1636  *  1    0  |   01      00      00
1637  *  1    2  |   01      11      11
1638  *  2    0  |   11      10(*)   00
1639  *  2    1  |   11      11      01
1640  *
1641  * (*) get_dumpable regards interim value of 10 as 11.
1642  */
1643 void set_dumpable(struct mm_struct *mm, int value)
1644 {
1645         switch (value) {
1646         case SUID_DUMPABLE_DISABLED:
1647                 clear_bit(MMF_DUMPABLE, &mm->flags);
1648                 smp_wmb();
1649                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1650                 break;
1651         case SUID_DUMPABLE_ENABLED:
1652                 set_bit(MMF_DUMPABLE, &mm->flags);
1653                 smp_wmb();
1654                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1655                 break;
1656         case SUID_DUMPABLE_SAFE:
1657                 set_bit(MMF_DUMP_SECURELY, &mm->flags);
1658                 smp_wmb();
1659                 set_bit(MMF_DUMPABLE, &mm->flags);
1660                 break;
1661         }
1662 }
1663
1664 int __get_dumpable(unsigned long mm_flags)
1665 {
1666         int ret;
1667
1668         ret = mm_flags & MMF_DUMPABLE_MASK;
1669         return (ret > SUID_DUMPABLE_ENABLED) ? SUID_DUMPABLE_SAFE : ret;
1670 }
1671
1672 int get_dumpable(struct mm_struct *mm)
1673 {
1674         return __get_dumpable(mm->flags);
1675 }
1676
1677 #ifdef __ARCH_WANT_SYS_EXECVE
1678 SYSCALL_DEFINE3(execve,
1679                 const char __user *, filename,
1680                 const char __user *const __user *, argv,
1681                 const char __user *const __user *, envp)
1682 {
1683         const char *path = getname(filename);
1684         int error = PTR_ERR(path);
1685         if (!IS_ERR(path)) {
1686                 error = do_execve(path, argv, envp, current_pt_regs());
1687                 putname(path);
1688         }
1689         return error;
1690 }
1691 #ifdef CONFIG_COMPAT
1692 asmlinkage long compat_sys_execve(const char __user * filename,
1693         const compat_uptr_t __user * argv,
1694         const compat_uptr_t __user * envp)
1695 {
1696         const char *path = getname(filename);
1697         int error = PTR_ERR(path);
1698         if (!IS_ERR(path)) {
1699                 error = compat_do_execve(path, argv, envp, current_pt_regs());
1700                 putname(path);
1701         }
1702         return error;
1703 }
1704 #endif
1705 #endif
1706
1707 #ifdef __ARCH_WANT_KERNEL_EXECVE
1708 int kernel_execve(const char *filename,
1709                   const char *const argv[],
1710                   const char *const envp[])
1711 {
1712         struct pt_regs regs;
1713         int ret;
1714
1715         memset(&regs, 0, sizeof(struct pt_regs));
1716         ret = do_execve(filename,
1717                         (const char __user *const __user *)argv,
1718                         (const char __user *const __user *)envp, &regs);
1719         if (ret < 0)
1720                 return ret;
1721
1722         /*
1723          * We were successful.  We won't be returning to our caller, but
1724          * instead to user space by manipulating the kernel stack.
1725          */
1726         ret_from_kernel_execve(current_pt_regs(), &regs);
1727 }
1728 #endif