fs/exec.c

   1 /*
   2  *  linux/fs/exec.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  * #!-checking implemented by tytso.
   9  */
  10 /*
  11  * Demand-loading implemented 01.12.91 - no need to read anything but
  12  * the header into memory. The inode of the executable is put into
  13  * "current->executable", and page faults do the actual loading. Clean.
  14  *
  15  * Once more I can proudly say that linux stood up to being changed: it
  16  * was less than 2 hours work to get demand-loading completely implemented.
  17  *
  18  * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
  19  * current->executable is only used by the procfs.  This allows a dispatch
  20  * table to check for several different types  of binary formats.  We keep
  21  * trying until we recognize the file or we run out of supported binary
  22  * formats.
  23  */
  24
  25 #include <linux/slab.h>
  26 #include <linux/file.h>
  27 #include <linux/fdtable.h>
  28 #include <linux/mm.h>
  29 #include <linux/vmacache.h>
  30 #include <linux/stat.h>
  31 #include <linux/fcntl.h>
  32 #include <linux/swap.h>
  33 #include <linux/string.h>
  34 #include <linux/init.h>
  35 #include <linux/sched/mm.h>
  36 #include <linux/sched/coredump.h>
  37 #include <linux/sched/signal.h>
  38 #include <linux/sched/numa_balancing.h>
  39 #include <linux/sched/task.h>
  40 #include <linux/pagemap.h>
  41 #include <linux/perf_event.h>
  42 #include <linux/highmem.h>
  43 #include <linux/spinlock.h>
  44 #include <linux/key.h>
  45 #include <linux/personality.h>
  46 #include <linux/binfmts.h>
  47 #include <linux/utsname.h>
  48 #include <linux/pid_namespace.h>
  49 #include <linux/module.h>
  50 #include <linux/namei.h>
  51 #include <linux/mount.h>
  52 #include <linux/security.h>
  53 #include <linux/syscalls.h>
  54 #include <linux/tsacct_kern.h>
  55 #include <linux/cn_proc.h>
  56 #include <linux/audit.h>
  57 #include <linux/tracehook.h>
  58 #include <linux/kmod.h>
  59 #include <linux/fsnotify.h>
  60 #include <linux/fs_struct.h>
  61 #include <linux/pipe_fs_i.h>
  62 #include <linux/oom.h>
  63 #include <linux/compat.h>
  64 #include <linux/vmalloc.h>
  65
  66 #include <linux/uaccess.h>
  67 #include <asm/mmu_context.h>
  68 #include <asm/tlb.h>
  69
  70 #include <trace/events/task.h>
  71 #include "internal.h"
  72
  73 #include <trace/events/sched.h>
  74
  75 int suid_dumpable = 0;
  76
  77 static LIST_HEAD(formats);
  78 static DEFINE_RWLOCK(binfmt_lock);
  79
  80 void __register_binfmt(struct linux_binfmt * fmt, int insert)
  81 {
  82         BUG_ON(!fmt);
  83         if (WARN_ON(!fmt->load_binary))
  84                 return;
  85         write_lock(&binfmt_lock);
  86         insert ? list_add(&fmt->lh, &formats) :
  87                  list_add_tail(&fmt->lh, &formats);
  88         write_unlock(&binfmt_lock);
  89 }
  90
  91 EXPORT_SYMBOL(__register_binfmt);
  92
  93 void unregister_binfmt(struct linux_binfmt * fmt)
  94 {
  95         write_lock(&binfmt_lock);
  96         list_del(&fmt->lh);
  97         write_unlock(&binfmt_lock);
  98 }
  99
 100 EXPORT_SYMBOL(unregister_binfmt);
 101
 102 static inline void put_binfmt(struct linux_binfmt * fmt)
 103 {
 104         module_put(fmt->module);
 105 }
 106
 107 bool path_noexec(const struct path *path)
 108 {
 109         return (path->mnt->mnt_flags & MNT_NOEXEC) ||
 110                (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
 111 }
 112
 113 #ifdef CONFIG_USELIB
 114 /*
 115  * Note that a shared library must be both readable and executable due to
 116  * security reasons.
 117  *
 118  * Also note that we take the address to load from from the file itself.
 119  */
 120 SYSCALL_DEFINE1(uselib, const char __user *, library)
 121 {
 122         struct linux_binfmt *fmt;
 123         struct file *file;
 124         struct filename *tmp = getname(library);
 125         int error = PTR_ERR(tmp);
 126         static const struct open_flags uselib_flags = {
 127                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 128                 .acc_mode = MAY_READ | MAY_EXEC,
 129                 .intent = LOOKUP_OPEN,
 130                 .lookup_flags = LOOKUP_FOLLOW,
 131         };
 132
 133         if (IS_ERR(tmp))
 134                 goto out;
 135
 136         file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
 137         putname(tmp);
 138         error = PTR_ERR(file);
 139         if (IS_ERR(file))
 140                 goto out;
 141
 142         error = -EINVAL;
 143         if (!S_ISREG(file_inode(file)->i_mode))
 144                 goto exit;
 145
 146         error = -EACCES;
 147         if (path_noexec(&file->f_path))
 148                 goto exit;
 149
 150         fsnotify_open(file);
 151
 152         error = -ENOEXEC;
 153
 154         read_lock(&binfmt_lock);
 155         list_for_each_entry(fmt, &formats, lh) {
 156                 if (!fmt->load_shlib)
 157                         continue;
 158                 if (!try_module_get(fmt->module))
 159                         continue;
 160                 read_unlock(&binfmt_lock);
 161                 error = fmt->load_shlib(file);
 162                 read_lock(&binfmt_lock);
 163                 put_binfmt(fmt);
 164                 if (error != -ENOEXEC)
 165                         break;
 166         }
 167         read_unlock(&binfmt_lock);
 168 exit:
 169         fput(file);
 170 out:
 171         return error;
 172 }
 173 #endif /* #ifdef CONFIG_USELIB */
 174
 175 #ifdef CONFIG_MMU
 176 /*
 177  * The nascent bprm->mm is not visible until exec_mmap() but it can
 178  * use a lot of memory, account these pages in current->mm temporary
 179  * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
 180  * change the counter back via acct_arg_size(0).
 181  */
 182 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 183 {
 184         struct mm_struct *mm = current->mm;
 185         long diff = (long)(pages - bprm->vma_pages);
 186
 187         if (!mm || !diff)
 188                 return;
 189
 190         bprm->vma_pages = pages;
 191         add_mm_counter(mm, MM_ANONPAGES, diff);
 192 }
 193
 194 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 195                 int write)
 196 {
 197         struct page *page;
 198         int ret;
 199         unsigned int gup_flags = FOLL_FORCE;
 200
 201 #ifdef CONFIG_STACK_GROWSUP
 202         if (write) {
 203                 ret = expand_downwards(bprm->vma, pos);
 204                 if (ret < 0)
 205                         return NULL;
 206         }
 207 #endif
 208
 209         if (write)
 210                 gup_flags |= FOLL_WRITE;
 211
 212         /*
 213          * We are doing an exec().  'current' is the process
 214          * doing the exec and bprm->mm is the new process's mm.
 215          */
 216         ret = get_user_pages_remote(current, bprm->mm, pos, 1, gup_flags,
 217                         &page, NULL, NULL);
 218         if (ret <= 0)
 219                 return NULL;
 220
 221         if (write) {
 222                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 223                 unsigned long ptr_size, limit;
 224
 225                 /*
 226                  * Since the stack will hold pointers to the strings, we
 227                  * must account for them as well.
 228                  *
 229                  * The size calculation is the entire vma while each arg page is
 230                  * built, so each time we get here it's calculating how far it
 231                  * is currently (rather than each call being just the newly
 232                  * added size from the arg page).  As a result, we need to
 233                  * always add the entire size of the pointers, so that on the
 234                  * last call to get_arg_page() we'll actually have the entire
 235                  * correct size.
 236                  */
 237                 ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
 238                 if (ptr_size > ULONG_MAX - size)
 239                         goto fail;
 240                 size += ptr_size;
 241
 242                 acct_arg_size(bprm, size / PAGE_SIZE);
 243
 244                 /*
 245                  * We've historically supported up to 32 pages (ARG_MAX)
 246                  * of argument strings even with small stacks
 247                  */
 248                 if (size <= ARG_MAX)
 249                         return page;
 250
 251                 /*
 252                  * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
 253                  * (whichever is smaller) for the argv+env strings.
 254                  * This ensures that:
 255                  *  - the remaining binfmt code will not run out of stack space,
 256                  *  - the program will have a reasonable amount of stack left
 257                  *    to work from.
 258                  */
 259                 limit = _STK_LIM / 4 * 3;
 260                 limit = min(limit, rlimit(RLIMIT_STACK) / 4);
 261                 if (size > limit)
 262                         goto fail;
 263         }
 264
 265         return page;
 266
 267 fail:
 268         put_page(page);
 269         return NULL;
 270 }
 271
 272 static void put_arg_page(struct page *page)
 273 {
 274         put_page(page);
 275 }
 276
 277 static void free_arg_pages(struct linux_binprm *bprm)
 278 {
 279 }
 280
 281 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 282                 struct page *page)
 283 {
 284         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 285 }
 286
 287 static int __bprm_mm_init(struct linux_binprm *bprm)
 288 {
 289         int err;
 290         struct vm_area_struct *vma = NULL;
 291         struct mm_struct *mm = bprm->mm;
 292
 293         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 294         if (!vma)
 295                 return -ENOMEM;
 296
 297         if (down_write_killable(&mm->mmap_sem)) {
 298                 err = -EINTR;
 299                 goto err_free;
 300         }
 301         vma->vm_mm = mm;
 302
 303         /*
 304          * Place the stack at the largest stack address the architecture
 305          * supports. Later, we'll move this to an appropriate place. We don't
 306          * use STACK_TOP because that can depend on attributes which aren't
 307          * configured yet.
 308          */
 309         BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 310         vma->vm_end = STACK_TOP_MAX;
 311         vma->vm_start = vma->vm_end - PAGE_SIZE;
 312         vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 313         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 314         INIT_LIST_HEAD(&vma->anon_vma_chain);
 315
 316         err = insert_vm_struct(mm, vma);
 317         if (err)
 318                 goto err;
 319
 320         mm->stack_vm = mm->total_vm = 1;
 321         arch_bprm_mm_init(mm, vma);
 322         up_write(&mm->mmap_sem);
 323         bprm->p = vma->vm_end - sizeof(void *);
 324         return 0;
 325 err:
 326         up_write(&mm->mmap_sem);
 327 err_free:
 328         bprm->vma = NULL;
 329         kmem_cache_free(vm_area_cachep, vma);
 330         return err;
 331 }
 332
 333 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 334 {
 335         return len <= MAX_ARG_STRLEN;
 336 }
 337
 338 #else
 339
 340 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 341 {
 342 }
 343
 344 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 345                 int write)
 346 {
 347         struct page *page;
 348
 349         page = bprm->page[pos / PAGE_SIZE];
 350         if (!page && write) {
 351                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 352                 if (!page)
 353                         return NULL;
 354                 bprm->page[pos / PAGE_SIZE] = page;
 355         }
 356
 357         return page;
 358 }
 359
 360 static void put_arg_page(struct page *page)
 361 {
 362 }
 363
 364 static void free_arg_page(struct linux_binprm *bprm, int i)
 365 {
 366         if (bprm->page[i]) {
 367                 __free_page(bprm->page[i]);
 368                 bprm->page[i] = NULL;
 369         }
 370 }
 371
 372 static void free_arg_pages(struct linux_binprm *bprm)
 373 {
 374         int i;
 375
 376         for (i = 0; i < MAX_ARG_PAGES; i++)
 377                 free_arg_page(bprm, i);
 378 }
 379
 380 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 381                 struct page *page)
 382 {
 383 }
 384
 385 static int __bprm_mm_init(struct linux_binprm *bprm)
 386 {
 387         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 388         return 0;
 389 }
 390
 391 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 392 {
 393         return len <= bprm->p;
 394 }
 395
 396 #endif /* CONFIG_MMU */
 397
 398 /*
 399  * Create a new mm_struct and populate it with a temporary stack
 400  * vm_area_struct.  We don't have enough context at this point to set the stack
 401  * flags, permissions, and offset, so we use temporary values.  We'll update
 402  * them later in setup_arg_pages().
 403  */
 404 static int bprm_mm_init(struct linux_binprm *bprm)
 405 {
 406         int err;
 407         struct mm_struct *mm = NULL;
 408
 409         bprm->mm = mm = mm_alloc();
 410         err = -ENOMEM;
 411         if (!mm)
 412                 goto err;
 413
 414         err = __bprm_mm_init(bprm);
 415         if (err)
 416                 goto err;
 417
 418         return 0;
 419
 420 err:
 421         if (mm) {
 422                 bprm->mm = NULL;
 423                 mmdrop(mm);
 424         }
 425
 426         return err;
 427 }
 428
 429 struct user_arg_ptr {
 430 #ifdef CONFIG_COMPAT
 431         bool is_compat;
 432 #endif
 433         union {
 434                 const char __user *const __user *native;
 435 #ifdef CONFIG_COMPAT
 436                 const compat_uptr_t __user *compat;
 437 #endif
 438         } ptr;
 439 };
 440
 441 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
 442 {
 443         const char __user *native;
 444
 445 #ifdef CONFIG_COMPAT
 446         if (unlikely(argv.is_compat)) {
 447                 compat_uptr_t compat;
 448
 449                 if (get_user(compat, argv.ptr.compat + nr))
 450                         return ERR_PTR(-EFAULT);
 451
 452                 return compat_ptr(compat);
 453         }
 454 #endif
 455
 456         if (get_user(native, argv.ptr.native + nr))
 457                 return ERR_PTR(-EFAULT);
 458
 459         return native;
 460 }
 461
 462 /*
 463  * count() counts the number of strings in array ARGV.
 464  */
 465 static int count(struct user_arg_ptr argv, int max)
 466 {
 467         int i = 0;
 468
 469         if (argv.ptr.native != NULL) {
 470                 for (;;) {
 471                         const char __user *p = get_user_arg_ptr(argv, i);
 472
 473                         if (!p)
 474                                 break;
 475
 476                         if (IS_ERR(p))
 477                                 return -EFAULT;
 478
 479                         if (i >= max)
 480                                 return -E2BIG;
 481                         ++i;
 482
 483                         if (fatal_signal_pending(current))
 484                                 return -ERESTARTNOHAND;
 485                         cond_resched();
 486                 }
 487         }
 488         return i;
 489 }
 490
 491 /*
 492  * 'copy_strings()' copies argument/environment strings from the old
 493  * processes's memory to the new process's stack.  The call to get_user_pages()
 494  * ensures the destination page is created and not swapped out.
 495  */
 496 static int copy_strings(int argc, struct user_arg_ptr argv,
 497                         struct linux_binprm *bprm)
 498 {
 499         struct page *kmapped_page = NULL;
 500         char *kaddr = NULL;
 501         unsigned long kpos = 0;
 502         int ret;
 503
 504         while (argc-- > 0) {
 505                 const char __user *str;
 506                 int len;
 507                 unsigned long pos;
 508
 509                 ret = -EFAULT;
 510                 str = get_user_arg_ptr(argv, argc);
 511                 if (IS_ERR(str))
 512                         goto out;
 513
 514                 len = strnlen_user(str, MAX_ARG_STRLEN);
 515                 if (!len)
 516                         goto out;
 517
 518                 ret = -E2BIG;
 519                 if (!valid_arg_len(bprm, len))
 520                         goto out;
 521
 522                 /* We're going to work our way backwords. */
 523                 pos = bprm->p;
 524                 str += len;
 525                 bprm->p -= len;
 526
 527                 while (len > 0) {
 528                         int offset, bytes_to_copy;
 529
 530                         if (fatal_signal_pending(current)) {
 531                                 ret = -ERESTARTNOHAND;
 532                                 goto out;
 533                         }
 534                         cond_resched();
 535
 536                         offset = pos % PAGE_SIZE;
 537                         if (offset == 0)
 538                                 offset = PAGE_SIZE;
 539
 540                         bytes_to_copy = offset;
 541                         if (bytes_to_copy > len)
 542                                 bytes_to_copy = len;
 543
 544                         offset -= bytes_to_copy;
 545                         pos -= bytes_to_copy;
 546                         str -= bytes_to_copy;
 547                         len -= bytes_to_copy;
 548
 549                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 550                                 struct page *page;
 551
 552                                 page = get_arg_page(bprm, pos, 1);
 553                                 if (!page) {
 554                                         ret = -E2BIG;
 555                                         goto out;
 556                                 }
 557
 558                                 if (kmapped_page) {
 559                                         flush_kernel_dcache_page(kmapped_page);
 560                                         kunmap(kmapped_page);
 561                                         put_arg_page(kmapped_page);
 562                                 }
 563                                 kmapped_page = page;
 564                                 kaddr = kmap(kmapped_page);
 565                                 kpos = pos & PAGE_MASK;
 566                                 flush_arg_page(bprm, kpos, kmapped_page);
 567                         }
 568                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 569                                 ret = -EFAULT;
 570                                 goto out;
 571                         }
 572                 }
 573         }
 574         ret = 0;
 575 out:
 576         if (kmapped_page) {
 577                 flush_kernel_dcache_page(kmapped_page);
 578                 kunmap(kmapped_page);
 579                 put_arg_page(kmapped_page);
 580         }
 581         return ret;
 582 }
 583
 584 /*
 585  * Like copy_strings, but get argv and its values from kernel memory.
 586  */
 587 int copy_strings_kernel(int argc, const char *const *__argv,
 588                         struct linux_binprm *bprm)
 589 {
 590         int r;
 591         mm_segment_t oldfs = get_fs();
 592         struct user_arg_ptr argv = {
 593                 .ptr.native = (const char __user *const  __user *)__argv,
 594         };
 595
 596         set_fs(KERNEL_DS);
 597         r = copy_strings(argc, argv, bprm);
 598         set_fs(oldfs);
 599
 600         return r;
 601 }
 602 EXPORT_SYMBOL(copy_strings_kernel);
 603
 604 #ifdef CONFIG_MMU
 605
 606 /*
 607  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 608  * the binfmt code determines where the new stack should reside, we shift it to
 609  * its final location.  The process proceeds as follows:
 610  *
 611  * 1) Use shift to calculate the new vma endpoints.
 612  * 2) Extend vma to cover both the old and new ranges.  This ensures the
 613  *    arguments passed to subsequent functions are consistent.
 614  * 3) Move vma's page tables to the new range.
 615  * 4) Free up any cleared pgd range.
 616  * 5) Shrink the vma to cover only the new range.
 617  */
 618 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 619 {
 620         struct mm_struct *mm = vma->vm_mm;
 621         unsigned long old_start = vma->vm_start;
 622         unsigned long old_end = vma->vm_end;
 623         unsigned long length = old_end - old_start;
 624         unsigned long new_start = old_start - shift;
 625         unsigned long new_end = old_end - shift;
 626         struct mmu_gather tlb;
 627
 628         BUG_ON(new_start > new_end);
 629
 630         /*
 631          * ensure there are no vmas between where we want to go
 632          * and where we are
 633          */
 634         if (vma != find_vma(mm, new_start))
 635                 return -EFAULT;
 636
 637         /*
 638          * cover the whole range: [new_start, old_end)
 639          */
 640         if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
 641                 return -ENOMEM;
 642
 643         /*
 644          * move the page tables downwards, on failure we rely on
 645          * process cleanup to remove whatever mess we made.
 646          */
 647         if (length != move_page_tables(vma, old_start,
 648                                        vma, new_start, length, false))
 649                 return -ENOMEM;
 650
 651         lru_add_drain();
 652         tlb_gather_mmu(&tlb, mm, old_start, old_end);
 653         if (new_end > old_start) {
 654                 /*
 655                  * when the old and new regions overlap clear from new_end.
 656                  */
 657                 free_pgd_range(&tlb, new_end, old_end, new_end,
 658                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 659         } else {
 660                 /*
 661                  * otherwise, clean from old_start; this is done to not touch
 662                  * the address space in [new_end, old_start) some architectures
 663                  * have constraints on va-space that make this illegal (IA64) -
 664                  * for the others its just a little faster.
 665                  */
 666                 free_pgd_range(&tlb, old_start, old_end, new_end,
 667                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 668         }
 669         tlb_finish_mmu(&tlb, old_start, old_end);
 670
 671         /*
 672          * Shrink the vma to just the new range.  Always succeeds.
 673          */
 674         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 675
 676         return 0;
 677 }
 678
 679 /*
 680  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 681  * the stack is optionally relocated, and some extra space is added.
 682  */
 683 int setup_arg_pages(struct linux_binprm *bprm,
 684                     unsigned long stack_top,
 685                     int executable_stack)
 686 {
 687         unsigned long ret;
 688         unsigned long stack_shift;
 689         struct mm_struct *mm = current->mm;
 690         struct vm_area_struct *vma = bprm->vma;
 691         struct vm_area_struct *prev = NULL;
 692         unsigned long vm_flags;
 693         unsigned long stack_base;
 694         unsigned long stack_size;
 695         unsigned long stack_expand;
 696         unsigned long rlim_stack;
 697
 698 #ifdef CONFIG_STACK_GROWSUP
 699         /* Limit stack size */
 700         stack_base = rlimit_max(RLIMIT_STACK);
 701         if (stack_base > STACK_SIZE_MAX)
 702                 stack_base = STACK_SIZE_MAX;
 703
 704         /* Add space for stack randomization. */
 705         stack_base += (STACK_RND_MASK << PAGE_SHIFT);
 706
 707         /* Make sure we didn't let the argument array grow too large. */
 708         if (vma->vm_end - vma->vm_start > stack_base)
 709                 return -ENOMEM;
 710
 711         stack_base = PAGE_ALIGN(stack_top - stack_base);
 712
 713         stack_shift = vma->vm_start - stack_base;
 714         mm->arg_start = bprm->p - stack_shift;
 715         bprm->p = vma->vm_end - stack_shift;
 716 #else
 717         stack_top = arch_align_stack(stack_top);
 718         stack_top = PAGE_ALIGN(stack_top);
 719
 720         if (unlikely(stack_top < mmap_min_addr) ||
 721             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 722                 return -ENOMEM;
 723
 724         stack_shift = vma->vm_end - stack_top;
 725
 726         bprm->p -= stack_shift;
 727         mm->arg_start = bprm->p;
 728 #endif
 729
 730         if (bprm->loader)
 731                 bprm->loader -= stack_shift;
 732         bprm->exec -= stack_shift;
 733
 734         if (down_write_killable(&mm->mmap_sem))
 735                 return -EINTR;
 736
 737         vm_flags = VM_STACK_FLAGS;
 738
 739         /*
 740          * Adjust stack execute permissions; explicitly enable for
 741          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 742          * (arch default) otherwise.
 743          */
 744         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 745                 vm_flags |= VM_EXEC;
 746         else if (executable_stack == EXSTACK_DISABLE_X)
 747                 vm_flags &= ~VM_EXEC;
 748         vm_flags |= mm->def_flags;
 749         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 750
 751         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 752                         vm_flags);
 753         if (ret)
 754                 goto out_unlock;
 755         BUG_ON(prev != vma);
 756
 757         /* Move stack pages down in memory. */
 758         if (stack_shift) {
 759                 ret = shift_arg_pages(vma, stack_shift);
 760                 if (ret)
 761                         goto out_unlock;
 762         }
 763
 764         /* mprotect_fixup is overkill to remove the temporary stack flags */
 765         vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
 766
 767         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
 768         stack_size = vma->vm_end - vma->vm_start;
 769         /*
 770          * Align this down to a page boundary as expand_stack
 771          * will align it up.
 772          */
 773         rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 774 #ifdef CONFIG_STACK_GROWSUP
 775         if (stack_size + stack_expand > rlim_stack)
 776                 stack_base = vma->vm_start + rlim_stack;
 777         else
 778                 stack_base = vma->vm_end + stack_expand;
 779 #else
 780         if (stack_size + stack_expand > rlim_stack)
 781                 stack_base = vma->vm_end - rlim_stack;
 782         else
 783                 stack_base = vma->vm_start - stack_expand;
 784 #endif
 785         current->mm->start_stack = bprm->p;
 786         ret = expand_stack(vma, stack_base);
 787         if (ret)
 788                 ret = -EFAULT;
 789
 790 out_unlock:
 791         up_write(&mm->mmap_sem);
 792         return ret;
 793 }
 794 EXPORT_SYMBOL(setup_arg_pages);
 795
 796 #else
 797
 798 /*
 799  * Transfer the program arguments and environment from the holding pages
 800  * onto the stack. The provided stack pointer is adjusted accordingly.
 801  */
 802 int transfer_args_to_stack(struct linux_binprm *bprm,
 803                            unsigned long *sp_location)
 804 {
 805         unsigned long index, stop, sp;
 806         int ret = 0;
 807
 808         stop = bprm->p >> PAGE_SHIFT;
 809         sp = *sp_location;
 810
 811         for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
 812                 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
 813                 char *src = kmap(bprm->page[index]) + offset;
 814                 sp -= PAGE_SIZE - offset;
 815                 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
 816                         ret = -EFAULT;
 817                 kunmap(bprm->page[index]);
 818                 if (ret)
 819                         goto out;
 820         }
 821
 822         *sp_location = sp;
 823
 824 out:
 825         return ret;
 826 }
 827 EXPORT_SYMBOL(transfer_args_to_stack);
 828
 829 #endif /* CONFIG_MMU */
 830
 831 static struct file *do_open_execat(int fd, struct filename *name, int flags)
 832 {
 833         struct file *file;
 834         int err;
 835         struct open_flags open_exec_flags = {
 836                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 837                 .acc_mode = MAY_EXEC,
 838                 .intent = LOOKUP_OPEN,
 839                 .lookup_flags = LOOKUP_FOLLOW,
 840         };
 841
 842         if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 843                 return ERR_PTR(-EINVAL);
 844         if (flags & AT_SYMLINK_NOFOLLOW)
 845                 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
 846         if (flags & AT_EMPTY_PATH)
 847                 open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
 848
 849         file = do_filp_open(fd, name, &open_exec_flags);
 850         if (IS_ERR(file))
 851                 goto out;
 852
 853         err = -EACCES;
 854         if (!S_ISREG(file_inode(file)->i_mode))
 855                 goto exit;
 856
 857         if (path_noexec(&file->f_path))
 858                 goto exit;
 859
 860         err = deny_write_access(file);
 861         if (err)
 862                 goto exit;
 863
 864         if (name->name[0] != '\0')
 865                 fsnotify_open(file);
 866
 867 out:
 868         return file;
 869
 870 exit:
 871         fput(file);
 872         return ERR_PTR(err);
 873 }
 874
 875 struct file *open_exec(const char *name)
 876 {
 877         struct filename *filename = getname_kernel(name);
 878         struct file *f = ERR_CAST(filename);
 879
 880         if (!IS_ERR(filename)) {
 881                 f = do_open_execat(AT_FDCWD, filename, 0);
 882                 putname(filename);
 883         }
 884         return f;
 885 }
 886 EXPORT_SYMBOL(open_exec);
 887
 888 int kernel_read(struct file *file, loff_t offset,
 889                 char *addr, unsigned long count)
 890 {
 891         mm_segment_t old_fs;
 892         loff_t pos = offset;
 893         int result;
 894
 895         old_fs = get_fs();
 896         set_fs(get_ds());
 897         /* The cast to a user pointer is valid due to the set_fs() */
 898         result = vfs_read(file, (void __user *)addr, count, &pos);
 899         set_fs(old_fs);
 900         return result;
 901 }
 902
 903 EXPORT_SYMBOL(kernel_read);
 904
 905 int kernel_read_file(struct file *file, void **buf, loff_t *size,
 906                      loff_t max_size, enum kernel_read_file_id id)
 907 {
 908         loff_t i_size, pos;
 909         ssize_t bytes = 0;
 910         int ret;
 911
 912         if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
 913                 return -EINVAL;
 914
 915         ret = security_kernel_read_file(file, id);
 916         if (ret)
 917                 return ret;
 918
 919         ret = deny_write_access(file);
 920         if (ret)
 921                 return ret;
 922
 923         i_size = i_size_read(file_inode(file));
 924         if (max_size > 0 && i_size > max_size) {
 925                 ret = -EFBIG;
 926                 goto out;
 927         }
 928         if (i_size <= 0) {
 929                 ret = -EINVAL;
 930                 goto out;
 931         }
 932
 933         if (id != READING_FIRMWARE_PREALLOC_BUFFER)
 934                 *buf = vmalloc(i_size);
 935         if (!*buf) {
 936                 ret = -ENOMEM;
 937                 goto out;
 938         }
 939
 940         pos = 0;
 941         while (pos < i_size) {
 942                 bytes = kernel_read(file, pos, (char *)(*buf) + pos,
 943                                     i_size - pos);
 944                 if (bytes < 0) {
 945                         ret = bytes;
 946                         goto out;
 947                 }
 948
 949                 if (bytes == 0)
 950                         break;
 951                 pos += bytes;
 952         }
 953
 954         if (pos != i_size) {
 955                 ret = -EIO;
 956                 goto out_free;
 957         }
 958
 959         ret = security_kernel_post_read_file(file, *buf, i_size, id);
 960         if (!ret)
 961                 *size = pos;
 962
 963 out_free:
 964         if (ret < 0) {
 965                 if (id != READING_FIRMWARE_PREALLOC_BUFFER) {
 966                         vfree(*buf);
 967                         *buf = NULL;
 968                 }
 969         }
 970
 971 out:
 972         allow_write_access(file);
 973         return ret;
 974 }
 975 EXPORT_SYMBOL_GPL(kernel_read_file);
 976
 977 int kernel_read_file_from_path(char *path, void **buf, loff_t *size,
 978                                loff_t max_size, enum kernel_read_file_id id)
 979 {
 980         struct file *file;
 981         int ret;
 982
 983         if (!path || !*path)
 984                 return -EINVAL;
 985
 986         file = filp_open(path, O_RDONLY, 0);
 987         if (IS_ERR(file))
 988                 return PTR_ERR(file);
 989
 990         ret = kernel_read_file(file, buf, size, max_size, id);
 991         fput(file);
 992         return ret;
 993 }
 994 EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
 995
 996 int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
 997                              enum kernel_read_file_id id)
 998 {
 999         struct fd f = fdget(fd);
1000         int ret = -EBADF;
1001
1002         if (!f.file)
1003                 goto out;
1004
1005         ret = kernel_read_file(f.file, buf, size, max_size, id);
1006 out:
1007         fdput(f);
1008         return ret;
1009 }
1010 EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);
1011
1012 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
1013 {
1014         ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
1015         if (res > 0)
1016                 flush_icache_range(addr, addr + len);
1017         return res;
1018 }
1019 EXPORT_SYMBOL(read_code);
1020
1021 static int exec_mmap(struct mm_struct *mm)
1022 {
1023         struct task_struct *tsk;
1024         struct mm_struct *old_mm, *active_mm;
1025
1026         /* Notify parent that we're no longer interested in the old VM */
1027         tsk = current;
1028         old_mm = current->mm;
1029         mm_release(tsk, old_mm);
1030
1031         if (old_mm) {
1032                 sync_mm_rss(old_mm);
1033                 /*
1034                  * Make sure that if there is a core dump in progress
1035                  * for the old mm, we get out and die instead of going
1036                  * through with the exec.  We must hold mmap_sem around
1037                  * checking core_state and changing tsk->mm.
1038                  */
1039                 down_read(&old_mm->mmap_sem);
1040                 if (unlikely(old_mm->core_state)) {
1041                         up_read(&old_mm->mmap_sem);
1042                         return -EINTR;
1043                 }
1044         }
1045         task_lock(tsk);
1046         active_mm = tsk->active_mm;
1047         tsk->mm = mm;
1048         tsk->active_mm = mm;
1049         activate_mm(active_mm, mm);
1050         tsk->mm->vmacache_seqnum = 0;
1051         vmacache_flush(tsk);
1052         task_unlock(tsk);
1053         if (old_mm) {
1054                 up_read(&old_mm->mmap_sem);
1055                 BUG_ON(active_mm != old_mm);
1056                 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
1057                 mm_update_next_owner(old_mm);
1058                 mmput(old_mm);
1059                 return 0;
1060         }
1061         mmdrop(active_mm);
1062         return 0;
1063 }
1064
1065 /*
1066  * This function makes sure the current process has its own signal table,
1067  * so that flush_signal_handlers can later reset the handlers without
1068  * disturbing other processes.  (Other processes might share the signal
1069  * table via the CLONE_SIGHAND option to clone().)
1070  */
1071 static int de_thread(struct task_struct *tsk)
1072 {
1073         struct signal_struct *sig = tsk->signal;
1074         struct sighand_struct *oldsighand = tsk->sighand;
1075         spinlock_t *lock = &oldsighand->siglock;
1076
1077         if (thread_group_empty(tsk))
1078                 goto no_thread_group;
1079
1080         /*
1081          * Kill all other threads in the thread group.
1082          */
1083         spin_lock_irq(lock);
1084         if (signal_group_exit(sig)) {
1085                 /*
1086                  * Another group action in progress, just
1087                  * return so that the signal is processed.
1088                  */
1089                 spin_unlock_irq(lock);
1090                 return -EAGAIN;
1091         }
1092
1093         sig->group_exit_task = tsk;
1094         sig->notify_count = zap_other_threads(tsk);
1095         if (!thread_group_leader(tsk))
1096                 sig->notify_count--;
1097
1098         while (sig->notify_count) {
1099                 __set_current_state(TASK_KILLABLE);
1100                 spin_unlock_irq(lock);
1101                 schedule();
1102                 if (unlikely(__fatal_signal_pending(tsk)))
1103                         goto killed;
1104                 spin_lock_irq(lock);
1105         }
1106         spin_unlock_irq(lock);
1107
1108         /*
1109          * At this point all other threads have exited, all we have to
1110          * do is to wait for the thread group leader to become inactive,
1111          * and to assume its PID:
1112          */
1113         if (!thread_group_leader(tsk)) {
1114                 struct task_struct *leader = tsk->group_leader;
1115
1116                 for (;;) {
1117                         cgroup_threadgroup_change_begin(tsk);
1118                         write_lock_irq(&tasklist_lock);
1119                         /*
1120                          * Do this under tasklist_lock to ensure that
1121                          * exit_notify() can't miss ->group_exit_task
1122                          */
1123                         sig->notify_count = -1;
1124                         if (likely(leader->exit_state))
1125                                 break;
1126                         __set_current_state(TASK_KILLABLE);
1127                         write_unlock_irq(&tasklist_lock);
1128                         cgroup_threadgroup_change_end(tsk);
1129                         schedule();
1130                         if (unlikely(__fatal_signal_pending(tsk)))
1131                                 goto killed;
1132                 }
1133
1134                 /*
1135                  * The only record we have of the real-time age of a
1136                  * process, regardless of execs it's done, is start_time.
1137                  * All the past CPU time is accumulated in signal_struct
1138                  * from sister threads now dead.  But in this non-leader
1139                  * exec, nothing survives from the original leader thread,
1140                  * whose birth marks the true age of this process now.
1141                  * When we take on its identity by switching to its PID, we
1142                  * also take its birthdate (always earlier than our own).
1143                  */
1144                 tsk->start_time = leader->start_time;
1145                 tsk->real_start_time = leader->real_start_time;
1146
1147                 BUG_ON(!same_thread_group(leader, tsk));
1148                 BUG_ON(has_group_leader_pid(tsk));
1149                 /*
1150                  * An exec() starts a new thread group with the
1151                  * TGID of the previous thread group. Rehash the
1152                  * two threads with a switched PID, and release
1153                  * the former thread group leader:
1154                  */
1155
1156                 /* Become a process group leader with the old leader's pid.
1157                  * The old leader becomes a thread of the this thread group.
1158                  * Note: The old leader also uses this pid until release_task
1159                  *       is called.  Odd but simple and correct.
1160                  */
1161                 tsk->pid = leader->pid;
1162                 change_pid(tsk, PIDTYPE_PID, task_pid(leader));
1163                 transfer_pid(leader, tsk, PIDTYPE_PGID);
1164                 transfer_pid(leader, tsk, PIDTYPE_SID);
1165
1166                 list_replace_rcu(&leader->tasks, &tsk->tasks);
1167                 list_replace_init(&leader->sibling, &tsk->sibling);
1168
1169                 tsk->group_leader = tsk;
1170                 leader->group_leader = tsk;
1171
1172                 tsk->exit_signal = SIGCHLD;
1173                 leader->exit_signal = -1;
1174
1175                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1176                 leader->exit_state = EXIT_DEAD;
1177
1178                 /*
1179                  * We are going to release_task()->ptrace_unlink() silently,
1180                  * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1181                  * the tracer wont't block again waiting for this thread.
1182                  */
1183                 if (unlikely(leader->ptrace))
1184                         __wake_up_parent(leader, leader->parent);
1185                 write_unlock_irq(&tasklist_lock);
1186                 cgroup_threadgroup_change_end(tsk);
1187
1188                 release_task(leader);
1189         }
1190
1191         sig->group_exit_task = NULL;
1192         sig->notify_count = 0;
1193
1194 no_thread_group:
1195         /* we have changed execution domain */
1196         tsk->exit_signal = SIGCHLD;
1197
1198 #ifdef CONFIG_POSIX_TIMERS
1199         exit_itimers(sig);
1200         flush_itimer_signals();
1201 #endif
1202
1203         if (atomic_read(&oldsighand->count) != 1) {
1204                 struct sighand_struct *newsighand;
1205                 /*
1206                  * This ->sighand is shared with the CLONE_SIGHAND
1207                  * but not CLONE_THREAD task, switch to the new one.
1208                  */
1209                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1210                 if (!newsighand)
1211                         return -ENOMEM;
1212
1213                 atomic_set(&newsighand->count, 1);
1214                 memcpy(newsighand->action, oldsighand->action,
1215                        sizeof(newsighand->action));
1216
1217                 write_lock_irq(&tasklist_lock);
1218                 spin_lock(&oldsighand->siglock);
1219                 rcu_assign_pointer(tsk->sighand, newsighand);
1220                 spin_unlock(&oldsighand->siglock);
1221                 write_unlock_irq(&tasklist_lock);
1222
1223                 __cleanup_sighand(oldsighand);
1224         }
1225
1226         BUG_ON(!thread_group_leader(tsk));
1227         return 0;
1228
1229 killed:
1230         /* protects against exit_notify() and __exit_signal() */
1231         read_lock(&tasklist_lock);
1232         sig->group_exit_task = NULL;
1233         sig->notify_count = 0;
1234         read_unlock(&tasklist_lock);
1235         return -EAGAIN;
1236 }
1237
1238 char *get_task_comm(char *buf, struct task_struct *tsk)
1239 {
1240         /* buf must be at least sizeof(tsk->comm) in size */
1241         task_lock(tsk);
1242         strncpy(buf, tsk->comm, sizeof(tsk->comm));
1243         task_unlock(tsk);
1244         return buf;
1245 }
1246 EXPORT_SYMBOL_GPL(get_task_comm);
1247
1248 /*
1249  * These functions flushes out all traces of the currently running executable
1250  * so that a new one can be started
1251  */
1252
1253 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1254 {
1255         task_lock(tsk);
1256         trace_task_rename(tsk, buf);
1257         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1258         task_unlock(tsk);
1259         perf_event_comm(tsk, exec);
1260 }
1261
1262 int flush_old_exec(struct linux_binprm * bprm)
1263 {
1264         int retval;
1265
1266         /*
1267          * Make sure we have a private signal table and that
1268          * we are unassociated from the previous thread group.
1269          */
1270         retval = de_thread(current);
1271         if (retval)
1272                 goto out;
1273
1274         /*
1275          * Must be called _before_ exec_mmap() as bprm->mm is
1276          * not visibile until then. This also enables the update
1277          * to be lockless.
1278          */
1279         set_mm_exe_file(bprm->mm, bprm->file);
1280
1281         /*
1282          * Release all of the old mmap stuff
1283          */
1284         acct_arg_size(bprm, 0);
1285         retval = exec_mmap(bprm->mm);
1286         if (retval)
1287                 goto out;
1288
1289         bprm->mm = NULL;                /* We're using it now */
1290
1291         set_fs(USER_DS);
1292         current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1293                                         PF_NOFREEZE | PF_NO_SETAFFINITY);
1294         flush_thread();
1295         current->personality &= ~bprm->per_clear;
1296
1297         /*
1298          * We have to apply CLOEXEC before we change whether the process is
1299          * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1300          * trying to access the should-be-closed file descriptors of a process
1301          * undergoing exec(2).
1302          */
1303         do_close_on_exec(current->files);
1304         return 0;
1305
1306 out:
1307         return retval;
1308 }
1309 EXPORT_SYMBOL(flush_old_exec);
1310
1311 void would_dump(struct linux_binprm *bprm, struct file *file)
1312 {
1313         struct inode *inode = file_inode(file);
1314         if (inode_permission(inode, MAY_READ) < 0) {
1315                 struct user_namespace *old, *user_ns;
1316                 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1317
1318                 /* Ensure mm->user_ns contains the executable */
1319                 user_ns = old = bprm->mm->user_ns;
1320                 while ((user_ns != &init_user_ns) &&
1321                        !privileged_wrt_inode_uidgid(user_ns, inode))
1322                         user_ns = user_ns->parent;
1323
1324                 if (old != user_ns) {
1325                         bprm->mm->user_ns = get_user_ns(user_ns);
1326                         put_user_ns(old);
1327                 }
1328         }
1329 }
1330 EXPORT_SYMBOL(would_dump);
1331
1332 void setup_new_exec(struct linux_binprm * bprm)
1333 {
1334         arch_pick_mmap_layout(current->mm);
1335
1336         /* This is the point of no return */
1337         current->sas_ss_sp = current->sas_ss_size = 0;
1338
1339         if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid()))
1340                 set_dumpable(current->mm, SUID_DUMP_USER);
1341         else
1342                 set_dumpable(current->mm, suid_dumpable);
1343
1344         arch_setup_new_exec();
1345         perf_event_exec();
1346         __set_task_comm(current, kbasename(bprm->filename), true);
1347
1348         /* Set the new mm task size. We have to do that late because it may
1349          * depend on TIF_32BIT which is only updated in flush_thread() on
1350          * some architectures like powerpc
1351          */
1352         current->mm->task_size = TASK_SIZE;
1353
1354         /* install the new credentials */
1355         if (!uid_eq(bprm->cred->uid, current_euid()) ||
1356             !gid_eq(bprm->cred->gid, current_egid())) {
1357                 current->pdeath_signal = 0;
1358         } else {
1359                 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
1360                         set_dumpable(current->mm, suid_dumpable);
1361         }
1362
1363         /* An exec changes our domain. We are no longer part of the thread
1364            group */
1365         current->self_exec_id++;
1366         flush_signal_handlers(current, 0);
1367 }
1368 EXPORT_SYMBOL(setup_new_exec);
1369
1370 /*
1371  * Prepare credentials and lock ->cred_guard_mutex.
1372  * install_exec_creds() commits the new creds and drops the lock.
1373  * Or, if exec fails before, free_bprm() should release ->cred and
1374  * and unlock.
1375  */
1376 int prepare_bprm_creds(struct linux_binprm *bprm)
1377 {
1378         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1379                 return -ERESTARTNOINTR;
1380
1381         bprm->cred = prepare_exec_creds();
1382         if (likely(bprm->cred))
1383                 return 0;
1384
1385         mutex_unlock(&current->signal->cred_guard_mutex);
1386         return -ENOMEM;
1387 }
1388
1389 static void free_bprm(struct linux_binprm *bprm)
1390 {
1391         free_arg_pages(bprm);
1392         if (bprm->cred) {
1393                 mutex_unlock(&current->signal->cred_guard_mutex);
1394                 abort_creds(bprm->cred);
1395         }
1396         if (bprm->file) {
1397                 allow_write_access(bprm->file);
1398                 fput(bprm->file);
1399         }
1400         /* If a binfmt changed the interp, free it. */
1401         if (bprm->interp != bprm->filename)
1402                 kfree(bprm->interp);
1403         kfree(bprm);
1404 }
1405
1406 int bprm_change_interp(char *interp, struct linux_binprm *bprm)
1407 {
1408         /* If a binfmt changed the interp, free it first. */
1409         if (bprm->interp != bprm->filename)
1410                 kfree(bprm->interp);
1411         bprm->interp = kstrdup(interp, GFP_KERNEL);
1412         if (!bprm->interp)
1413                 return -ENOMEM;
1414         return 0;
1415 }
1416 EXPORT_SYMBOL(bprm_change_interp);
1417
1418 /*
1419  * install the new credentials for this executable
1420  */
1421 void install_exec_creds(struct linux_binprm *bprm)
1422 {
1423         security_bprm_committing_creds(bprm);
1424
1425         commit_creds(bprm->cred);
1426         bprm->cred = NULL;
1427
1428         /*
1429          * Disable monitoring for regular users
1430          * when executing setuid binaries. Must
1431          * wait until new credentials are committed
1432          * by commit_creds() above
1433          */
1434         if (get_dumpable(current->mm) != SUID_DUMP_USER)
1435                 perf_event_exit_task(current);
1436         /*
1437          * cred_guard_mutex must be held at least to this point to prevent
1438          * ptrace_attach() from altering our determination of the task's
1439          * credentials; any time after this it may be unlocked.
1440          */
1441         security_bprm_committed_creds(bprm);
1442         mutex_unlock(&current->signal->cred_guard_mutex);
1443 }
1444 EXPORT_SYMBOL(install_exec_creds);
1445
1446 /*
1447  * determine how safe it is to execute the proposed program
1448  * - the caller must hold ->cred_guard_mutex to protect against
1449  *   PTRACE_ATTACH or seccomp thread-sync
1450  */
1451 static void check_unsafe_exec(struct linux_binprm *bprm)
1452 {
1453         struct task_struct *p = current, *t;
1454         unsigned n_fs;
1455
1456         if (p->ptrace)
1457                 bprm->unsafe |= LSM_UNSAFE_PTRACE;
1458
1459         /*
1460          * This isn't strictly necessary, but it makes it harder for LSMs to
1461          * mess up.
1462          */
1463         if (task_no_new_privs(current))
1464                 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1465
1466         t = p;
1467         n_fs = 1;
1468         spin_lock(&p->fs->lock);
1469         rcu_read_lock();
1470         while_each_thread(p, t) {
1471                 if (t->fs == p->fs)
1472                         n_fs++;
1473         }
1474         rcu_read_unlock();
1475
1476         if (p->fs->users > n_fs)
1477                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1478         else
1479                 p->fs->in_exec = 1;
1480         spin_unlock(&p->fs->lock);
1481 }
1482
1483 static void bprm_fill_uid(struct linux_binprm *bprm)
1484 {
1485         struct inode *inode;
1486         unsigned int mode;
1487         kuid_t uid;
1488         kgid_t gid;
1489
1490         /*
1491          * Since this can be called multiple times (via prepare_binprm),
1492          * we must clear any previous work done when setting set[ug]id
1493          * bits from any earlier bprm->file uses (for example when run
1494          * first for a setuid script then again for its interpreter).
1495          */
1496         bprm->cred->euid = current_euid();
1497         bprm->cred->egid = current_egid();
1498
1499         if (!mnt_may_suid(bprm->file->f_path.mnt))
1500                 return;
1501
1502         if (task_no_new_privs(current))
1503                 return;
1504
1505         inode = bprm->file->f_path.dentry->d_inode;
1506         mode = READ_ONCE(inode->i_mode);
1507         if (!(mode & (S_ISUID|S_ISGID)))
1508                 return;
1509
1510         /* Be careful if suid/sgid is set */
1511         inode_lock(inode);
1512
1513         /* reload atomically mode/uid/gid now that lock held */
1514         mode = inode->i_mode;
1515         uid = inode->i_uid;
1516         gid = inode->i_gid;
1517         inode_unlock(inode);
1518
1519         /* We ignore suid/sgid if there are no mappings for them in the ns */
1520         if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1521                  !kgid_has_mapping(bprm->cred->user_ns, gid))
1522                 return;
1523
1524         if (mode & S_ISUID) {
1525                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1526                 bprm->cred->euid = uid;
1527         }
1528
1529         if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1530                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1531                 bprm->cred->egid = gid;
1532         }
1533 }
1534
1535 /*
1536  * Fill the binprm structure from the inode.
1537  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1538  *
1539  * This may be called multiple times for binary chains (scripts for example).
1540  */
1541 int prepare_binprm(struct linux_binprm *bprm)
1542 {
1543         int retval;
1544
1545         bprm_fill_uid(bprm);
1546
1547         /* fill in binprm security blob */
1548         retval = security_bprm_set_creds(bprm);
1549         if (retval)
1550                 return retval;
1551         bprm->cred_prepared = 1;
1552
1553         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1554         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1555 }
1556
1557 EXPORT_SYMBOL(prepare_binprm);
1558
1559 /*
1560  * Arguments are '\0' separated strings found at the location bprm->p
1561  * points to; chop off the first by relocating brpm->p to right after
1562  * the first '\0' encountered.
1563  */
1564 int remove_arg_zero(struct linux_binprm *bprm)
1565 {
1566         int ret = 0;
1567         unsigned long offset;
1568         char *kaddr;
1569         struct page *page;
1570
1571         if (!bprm->argc)
1572                 return 0;
1573
1574         do {
1575                 offset = bprm->p & ~PAGE_MASK;
1576                 page = get_arg_page(bprm, bprm->p, 0);
1577                 if (!page) {
1578                         ret = -EFAULT;
1579                         goto out;
1580                 }
1581                 kaddr = kmap_atomic(page);
1582
1583                 for (; offset < PAGE_SIZE && kaddr[offset];
1584                                 offset++, bprm->p++)
1585                         ;
1586
1587                 kunmap_atomic(kaddr);
1588                 put_arg_page(page);
1589         } while (offset == PAGE_SIZE);
1590
1591         bprm->p++;
1592         bprm->argc--;
1593         ret = 0;
1594
1595 out:
1596         return ret;
1597 }
1598 EXPORT_SYMBOL(remove_arg_zero);
1599
1600 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1601 /*
1602  * cycle the list of binary formats handler, until one recognizes the image
1603  */
1604 int search_binary_handler(struct linux_binprm *bprm)
1605 {
1606         bool need_retry = IS_ENABLED(CONFIG_MODULES);
1607         struct linux_binfmt *fmt;
1608         int retval;
1609
1610         /* This allows 4 levels of binfmt rewrites before failing hard. */
1611         if (bprm->recursion_depth > 5)
1612                 return -ELOOP;
1613
1614         retval = security_bprm_check(bprm);
1615         if (retval)
1616                 return retval;
1617
1618         retval = -ENOENT;
1619  retry:
1620         read_lock(&binfmt_lock);
1621         list_for_each_entry(fmt, &formats, lh) {
1622                 if (!try_module_get(fmt->module))
1623                         continue;
1624                 read_unlock(&binfmt_lock);
1625                 bprm->recursion_depth++;
1626                 retval = fmt->load_binary(bprm);
1627                 read_lock(&binfmt_lock);
1628                 put_binfmt(fmt);
1629                 bprm->recursion_depth--;
1630                 if (retval < 0 && !bprm->mm) {
1631                         /* we got to flush_old_exec() and failed after it */
1632                         read_unlock(&binfmt_lock);
1633                         force_sigsegv(SIGSEGV, current);
1634                         return retval;
1635                 }
1636                 if (retval != -ENOEXEC || !bprm->file) {
1637                         read_unlock(&binfmt_lock);
1638                         return retval;
1639                 }
1640         }
1641         read_unlock(&binfmt_lock);
1642
1643         if (need_retry) {
1644                 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1645                     printable(bprm->buf[2]) && printable(bprm->buf[3]))
1646                         return retval;
1647                 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1648                         return retval;
1649                 need_retry = false;
1650                 goto retry;
1651         }
1652
1653         return retval;
1654 }
1655 EXPORT_SYMBOL(search_binary_handler);
1656
1657 static int exec_binprm(struct linux_binprm *bprm)
1658 {
1659         pid_t old_pid, old_vpid;
1660         int ret;
1661
1662         /* Need to fetch pid before load_binary changes it */
1663         old_pid = current->pid;
1664         rcu_read_lock();
1665         old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1666         rcu_read_unlock();
1667
1668         ret = search_binary_handler(bprm);
1669         if (ret >= 0) {
1670                 audit_bprm(bprm);
1671                 trace_sched_process_exec(current, old_pid, bprm);
1672                 ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1673                 proc_exec_connector(current);
1674         }
1675
1676         return ret;
1677 }
1678
1679 /*
1680  * sys_execve() executes a new program.
1681  */
1682 static int do_execveat_common(int fd, struct filename *filename,
1683                               struct user_arg_ptr argv,
1684                               struct user_arg_ptr envp,
1685                               int flags)
1686 {
1687         char *pathbuf = NULL;
1688         struct linux_binprm *bprm;
1689         struct file *file;
1690         struct files_struct *displaced;
1691         int retval;
1692
1693         if (IS_ERR(filename))
1694                 return PTR_ERR(filename);
1695
1696         /*
1697          * We move the actual failure in case of RLIMIT_NPROC excess from
1698          * set*uid() to execve() because too many poorly written programs
1699          * don't check setuid() return code.  Here we additionally recheck
1700          * whether NPROC limit is still exceeded.
1701          */
1702         if ((current->flags & PF_NPROC_EXCEEDED) &&
1703             atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1704                 retval = -EAGAIN;
1705                 goto out_ret;
1706         }
1707
1708         /* We're below the limit (still or again), so we don't want to make
1709          * further execve() calls fail. */
1710         current->flags &= ~PF_NPROC_EXCEEDED;
1711
1712         retval = unshare_files(&displaced);
1713         if (retval)
1714                 goto out_ret;
1715
1716         retval = -ENOMEM;
1717         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1718         if (!bprm)
1719                 goto out_files;
1720
1721         retval = prepare_bprm_creds(bprm);
1722         if (retval)
1723                 goto out_free;
1724
1725         check_unsafe_exec(bprm);
1726         current->in_execve = 1;
1727
1728         file = do_open_execat(fd, filename, flags);
1729         retval = PTR_ERR(file);
1730         if (IS_ERR(file))
1731                 goto out_unmark;
1732
1733         sched_exec();
1734
1735         bprm->file = file;
1736         if (fd == AT_FDCWD || filename->name[0] == '/') {
1737                 bprm->filename = filename->name;
1738         } else {
1739                 if (filename->name[0] == '\0')
1740                         pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d", fd);
1741                 else
1742                         pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d/%s",
1743                                             fd, filename->name);
1744                 if (!pathbuf) {
1745                         retval = -ENOMEM;
1746                         goto out_unmark;
1747                 }
1748                 /*
1749                  * Record that a name derived from an O_CLOEXEC fd will be
1750                  * inaccessible after exec. Relies on having exclusive access to
1751                  * current->files (due to unshare_files above).
1752                  */
1753                 if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
1754                         bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1755                 bprm->filename = pathbuf;
1756         }
1757         bprm->interp = bprm->filename;
1758
1759         retval = bprm_mm_init(bprm);
1760         if (retval)
1761                 goto out_unmark;
1762
1763         bprm->argc = count(argv, MAX_ARG_STRINGS);
1764         if ((retval = bprm->argc) < 0)
1765                 goto out;
1766
1767         bprm->envc = count(envp, MAX_ARG_STRINGS);
1768         if ((retval = bprm->envc) < 0)
1769                 goto out;
1770
1771         retval = prepare_binprm(bprm);
1772         if (retval < 0)
1773                 goto out;
1774
1775         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1776         if (retval < 0)
1777                 goto out;
1778
1779         bprm->exec = bprm->p;
1780         retval = copy_strings(bprm->envc, envp, bprm);
1781         if (retval < 0)
1782                 goto out;
1783
1784         retval = copy_strings(bprm->argc, argv, bprm);
1785         if (retval < 0)
1786                 goto out;
1787
1788         would_dump(bprm, bprm->file);
1789
1790         retval = exec_binprm(bprm);
1791         if (retval < 0)
1792                 goto out;
1793
1794         /* execve succeeded */
1795         current->fs->in_exec = 0;
1796         current->in_execve = 0;
1797         acct_update_integrals(current);
1798         task_numa_free(current);
1799         free_bprm(bprm);
1800         kfree(pathbuf);
1801         putname(filename);
1802         if (displaced)
1803                 put_files_struct(displaced);
1804         return retval;
1805
1806 out:
1807         if (bprm->mm) {
1808                 acct_arg_size(bprm, 0);
1809                 mmput(bprm->mm);
1810         }
1811
1812 out_unmark:
1813         current->fs->in_exec = 0;
1814         current->in_execve = 0;
1815
1816 out_free:
1817         free_bprm(bprm);
1818         kfree(pathbuf);
1819
1820 out_files:
1821         if (displaced)
1822                 reset_files_struct(displaced);
1823 out_ret:
1824         putname(filename);
1825         return retval;
1826 }
1827
1828 int do_execve(struct filename *filename,
1829         const char __user *const __user *__argv,
1830         const char __user *const __user *__envp)
1831 {
1832         struct user_arg_ptr argv = { .ptr.native = __argv };
1833         struct user_arg_ptr envp = { .ptr.native = __envp };
1834         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1835 }
1836
1837 int do_execveat(int fd, struct filename *filename,
1838                 const char __user *const __user *__argv,
1839                 const char __user *const __user *__envp,
1840                 int flags)
1841 {
1842         struct user_arg_ptr argv = { .ptr.native = __argv };
1843         struct user_arg_ptr envp = { .ptr.native = __envp };
1844
1845         return do_execveat_common(fd, filename, argv, envp, flags);
1846 }
1847
1848 #ifdef CONFIG_COMPAT
1849 static int compat_do_execve(struct filename *filename,
1850         const compat_uptr_t __user *__argv,
1851         const compat_uptr_t __user *__envp)
1852 {
1853         struct user_arg_ptr argv = {
1854                 .is_compat = true,
1855                 .ptr.compat = __argv,
1856         };
1857         struct user_arg_ptr envp = {
1858                 .is_compat = true,
1859                 .ptr.compat = __envp,
1860         };
1861         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1862 }
1863
1864 static int compat_do_execveat(int fd, struct filename *filename,
1865                               const compat_uptr_t __user *__argv,
1866                               const compat_uptr_t __user *__envp,
1867                               int flags)
1868 {
1869         struct user_arg_ptr argv = {
1870                 .is_compat = true,
1871                 .ptr.compat = __argv,
1872         };
1873         struct user_arg_ptr envp = {
1874                 .is_compat = true,
1875                 .ptr.compat = __envp,
1876         };
1877         return do_execveat_common(fd, filename, argv, envp, flags);
1878 }
1879 #endif
1880
1881 void set_binfmt(struct linux_binfmt *new)
1882 {
1883         struct mm_struct *mm = current->mm;
1884
1885         if (mm->binfmt)
1886                 module_put(mm->binfmt->module);
1887
1888         mm->binfmt = new;
1889         if (new)
1890                 __module_get(new->module);
1891 }
1892 EXPORT_SYMBOL(set_binfmt);
1893
1894 /*
1895  * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
1896  */
1897 void set_dumpable(struct mm_struct *mm, int value)
1898 {
1899         unsigned long old, new;
1900
1901         if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
1902                 return;
1903
1904         do {
1905                 old = ACCESS_ONCE(mm->flags);
1906                 new = (old & ~MMF_DUMPABLE_MASK) | value;
1907         } while (cmpxchg(&mm->flags, old, new) != old);
1908 }
1909
1910 SYSCALL_DEFINE3(execve,
1911                 const char __user *, filename,
1912                 const char __user *const __user *, argv,
1913                 const char __user *const __user *, envp)
1914 {
1915         return do_execve(getname(filename), argv, envp);
1916 }
1917
1918 SYSCALL_DEFINE5(execveat,
1919                 int, fd, const char __user *, filename,
1920                 const char __user *const __user *, argv,
1921                 const char __user *const __user *, envp,
1922                 int, flags)
1923 {
1924         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1925
1926         return do_execveat(fd,
1927                            getname_flags(filename, lookup_flags, NULL),
1928                            argv, envp, flags);
1929 }
1930
1931 #ifdef CONFIG_COMPAT
1932 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
1933         const compat_uptr_t __user *, argv,
1934         const compat_uptr_t __user *, envp)
1935 {
1936         return compat_do_execve(getname(filename), argv, envp);
1937 }
1938
1939 COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
1940                        const char __user *, filename,
1941                        const compat_uptr_t __user *, argv,
1942                        const compat_uptr_t __user *, envp,
1943                        int,  flags)
1944 {
1945         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1946
1947         return compat_do_execveat(fd,
1948                                   getname_flags(filename, lookup_flags, NULL),
1949                                   argv, envp, flags);
1950 }
1951 #endif