fs/exec.c

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