fs/exec.c

   1 /*
   2  *  linux/fs/exec.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  * #!-checking implemented by tytso.
   9  */
  10 /*
  11  * Demand-loading implemented 01.12.91 - no need to read anything but
  12  * the header into memory. The inode of the executable is put into
  13  * "current->executable", and page faults do the actual loading. Clean.
  14  *
  15  * Once more I can proudly say that linux stood up to being changed: it
  16  * was less than 2 hours work to get demand-loading completely implemented.
  17  *
  18  * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
  19  * current->executable is only used by the procfs.  This allows a dispatch
  20  * table to check for several different types  of binary formats.  We keep
  21  * trying until we recognize the file or we run out of supported binary
  22  * formats.
  23  */
  24
  25 #include <linux/slab.h>
  26 #include <linux/file.h>
  27 #include <linux/fdtable.h>
  28 #include <linux/mm.h>
  29 #include <linux/stat.h>
  30 #include <linux/fcntl.h>
  31 #include <linux/smp_lock.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/proc_fs.h>
  47 #include <linux/mount.h>
  48 #include <linux/security.h>
  49 #include <linux/ima.h>
  50 #include <linux/syscalls.h>
  51 #include <linux/tsacct_kern.h>
  52 #include <linux/cn_proc.h>
  53 #include <linux/audit.h>
  54 #include <linux/tracehook.h>
  55 #include <linux/kmod.h>
  56 #include <linux/fsnotify.h>
  57 #include <linux/fs_struct.h>
  58 #include <linux/pipe_fs_i.h>
  59
  60 #include <asm/uaccess.h>
  61 #include <asm/mmu_context.h>
  62 #include <asm/tlb.h>
  63 #include "internal.h"
  64
  65 int core_uses_pid;
  66 char core_pattern[CORENAME_MAX_SIZE] = "core";
  67 unsigned int core_pipe_limit;
  68 int suid_dumpable = 0;
  69
  70 /* The maximal length of core_pattern is also specified in sysctl.c */
  71
  72 static LIST_HEAD(formats);
  73 static DEFINE_RWLOCK(binfmt_lock);
  74
  75 int __register_binfmt(struct linux_binfmt * fmt, int insert)
  76 {
  77         if (!fmt)
  78                 return -EINVAL;
  79         write_lock(&binfmt_lock);
  80         insert ? list_add(&fmt->lh, &formats) :
  81                  list_add_tail(&fmt->lh, &formats);
  82         write_unlock(&binfmt_lock);
  83         return 0;
  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 /*
 103  * Note that a shared library must be both readable and executable due to
 104  * security reasons.
 105  *
 106  * Also note that we take the address to load from from the file itself.
 107  */
 108 SYSCALL_DEFINE1(uselib, const char __user *, library)
 109 {
 110         struct file *file;
 111         char *tmp = getname(library);
 112         int error = PTR_ERR(tmp);
 113
 114         if (IS_ERR(tmp))
 115                 goto out;
 116
 117         file = do_filp_open(AT_FDCWD, tmp,
 118                                 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0,
 119                                 MAY_READ | MAY_EXEC | MAY_OPEN);
 120         putname(tmp);
 121         error = PTR_ERR(file);
 122         if (IS_ERR(file))
 123                 goto out;
 124
 125         error = -EINVAL;
 126         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
 127                 goto exit;
 128
 129         error = -EACCES;
 130         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 131                 goto exit;
 132
 133         fsnotify_open(file->f_path.dentry);
 134
 135         error = -ENOEXEC;
 136         if(file->f_op) {
 137                 struct linux_binfmt * fmt;
 138
 139                 read_lock(&binfmt_lock);
 140                 list_for_each_entry(fmt, &formats, lh) {
 141                         if (!fmt->load_shlib)
 142                                 continue;
 143                         if (!try_module_get(fmt->module))
 144                                 continue;
 145                         read_unlock(&binfmt_lock);
 146                         error = fmt->load_shlib(file);
 147                         read_lock(&binfmt_lock);
 148                         put_binfmt(fmt);
 149                         if (error != -ENOEXEC)
 150                                 break;
 151                 }
 152                 read_unlock(&binfmt_lock);
 153         }
 154 exit:
 155         fput(file);
 156 out:
 157         return error;
 158 }
 159
 160 #ifdef CONFIG_MMU
 161
 162 void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 163 {
 164         struct mm_struct *mm = current->mm;
 165         long diff = (long)(pages - bprm->vma_pages);
 166
 167         if (!mm || !diff)
 168                 return;
 169
 170         bprm->vma_pages = pages;
 171
 172         down_write(&mm->mmap_sem);
 173         mm->total_vm += diff;
 174         up_write(&mm->mmap_sem);
 175 }
 176
 177 struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 178                 int write)
 179 {
 180         struct page *page;
 181         int ret;
 182
 183 #ifdef CONFIG_STACK_GROWSUP
 184         if (write) {
 185                 ret = expand_stack_downwards(bprm->vma, pos);
 186                 if (ret < 0)
 187                         return NULL;
 188         }
 189 #endif
 190         ret = get_user_pages(current, bprm->mm, pos,
 191                         1, write, 1, &page, NULL);
 192         if (ret <= 0)
 193                 return NULL;
 194
 195         if (write) {
 196                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 197                 struct rlimit *rlim;
 198
 199                 acct_arg_size(bprm, size / PAGE_SIZE);
 200
 201                 /*
 202                  * We've historically supported up to 32 pages (ARG_MAX)
 203                  * of argument strings even with small stacks
 204                  */
 205                 if (size <= ARG_MAX)
 206                         return page;
 207
 208                 /*
 209                  * Limit to 1/4-th the stack size for the argv+env strings.
 210                  * This ensures that:
 211                  *  - the remaining binfmt code will not run out of stack space,
 212                  *  - the program will have a reasonable amount of stack left
 213                  *    to work from.
 214                  */
 215                 rlim = current->signal->rlim;
 216                 if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
 217                         put_page(page);
 218                         return NULL;
 219                 }
 220         }
 221
 222         return page;
 223 }
 224
 225 static void put_arg_page(struct page *page)
 226 {
 227         put_page(page);
 228 }
 229
 230 static void free_arg_page(struct linux_binprm *bprm, int i)
 231 {
 232 }
 233
 234 static void free_arg_pages(struct linux_binprm *bprm)
 235 {
 236 }
 237
 238 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 239                 struct page *page)
 240 {
 241         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 242 }
 243
 244 static int __bprm_mm_init(struct linux_binprm *bprm)
 245 {
 246         int err;
 247         struct vm_area_struct *vma = NULL;
 248         struct mm_struct *mm = bprm->mm;
 249
 250         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 251         if (!vma)
 252                 return -ENOMEM;
 253
 254         down_write(&mm->mmap_sem);
 255         vma->vm_mm = mm;
 256
 257         /*
 258          * Place the stack at the largest stack address the architecture
 259          * supports. Later, we'll move this to an appropriate place. We don't
 260          * use STACK_TOP because that can depend on attributes which aren't
 261          * configured yet.
 262          */
 263         vma->vm_end = STACK_TOP_MAX;
 264         vma->vm_start = vma->vm_end - PAGE_SIZE;
 265         vma->vm_flags = VM_STACK_FLAGS;
 266         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 267
 268         err = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1);
 269         if (err)
 270                 goto err;
 271
 272         err = insert_vm_struct(mm, vma);
 273         if (err)
 274                 goto err;
 275
 276         mm->stack_vm = mm->total_vm = 1;
 277         up_write(&mm->mmap_sem);
 278         bprm->p = vma->vm_end - sizeof(void *);
 279         return 0;
 280 err:
 281         up_write(&mm->mmap_sem);
 282         bprm->vma = NULL;
 283         kmem_cache_free(vm_area_cachep, vma);
 284         return err;
 285 }
 286
 287 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 288 {
 289         return len <= MAX_ARG_STRLEN;
 290 }
 291
 292 #else
 293
 294 void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 295 {
 296 }
 297
 298 struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 299                 int write)
 300 {
 301         struct page *page;
 302
 303         page = bprm->page[pos / PAGE_SIZE];
 304         if (!page && write) {
 305                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 306                 if (!page)
 307                         return NULL;
 308                 bprm->page[pos / PAGE_SIZE] = page;
 309         }
 310
 311         return page;
 312 }
 313
 314 static void put_arg_page(struct page *page)
 315 {
 316 }
 317
 318 static void free_arg_page(struct linux_binprm *bprm, int i)
 319 {
 320         if (bprm->page[i]) {
 321                 __free_page(bprm->page[i]);
 322                 bprm->page[i] = NULL;
 323         }
 324 }
 325
 326 static void free_arg_pages(struct linux_binprm *bprm)
 327 {
 328         int i;
 329
 330         for (i = 0; i < MAX_ARG_PAGES; i++)
 331                 free_arg_page(bprm, i);
 332 }
 333
 334 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 335                 struct page *page)
 336 {
 337 }
 338
 339 static int __bprm_mm_init(struct linux_binprm *bprm)
 340 {
 341         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 342         return 0;
 343 }
 344
 345 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 346 {
 347         return len <= bprm->p;
 348 }
 349
 350 #endif /* CONFIG_MMU */
 351
 352 /*
 353  * Create a new mm_struct and populate it with a temporary stack
 354  * vm_area_struct.  We don't have enough context at this point to set the stack
 355  * flags, permissions, and offset, so we use temporary values.  We'll update
 356  * them later in setup_arg_pages().
 357  */
 358 int bprm_mm_init(struct linux_binprm *bprm)
 359 {
 360         int err;
 361         struct mm_struct *mm = NULL;
 362
 363         bprm->mm = mm = mm_alloc();
 364         err = -ENOMEM;
 365         if (!mm)
 366                 goto err;
 367
 368         err = init_new_context(current, mm);
 369         if (err)
 370                 goto err;
 371
 372         err = __bprm_mm_init(bprm);
 373         if (err)
 374                 goto err;
 375
 376         return 0;
 377
 378 err:
 379         if (mm) {
 380                 bprm->mm = NULL;
 381                 mmdrop(mm);
 382         }
 383
 384         return err;
 385 }
 386
 387 /*
 388  * count() counts the number of strings in array ARGV.
 389  */
 390 static int count(char __user * __user * argv, int max)
 391 {
 392         int i = 0;
 393
 394         if (argv != NULL) {
 395                 for (;;) {
 396                         char __user * p;
 397
 398                         if (get_user(p, argv))
 399                                 return -EFAULT;
 400                         if (!p)
 401                                 break;
 402                         argv++;
 403                         if (i++ >= max)
 404                                 return -E2BIG;
 405
 406                         if (fatal_signal_pending(current))
 407                                 return -ERESTARTNOHAND;
 408                         cond_resched();
 409                 }
 410         }
 411         return i;
 412 }
 413
 414 /*
 415  * 'copy_strings()' copies argument/environment strings from the old
 416  * processes's memory to the new process's stack.  The call to get_user_pages()
 417  * ensures the destination page is created and not swapped out.
 418  */
 419 static int copy_strings(int argc, char __user * __user * argv,
 420                         struct linux_binprm *bprm)
 421 {
 422         struct page *kmapped_page = NULL;
 423         char *kaddr = NULL;
 424         unsigned long kpos = 0;
 425         int ret;
 426
 427         while (argc-- > 0) {
 428                 char __user *str;
 429                 int len;
 430                 unsigned long pos;
 431
 432                 if (get_user(str, argv+argc) ||
 433                                 !(len = strnlen_user(str, MAX_ARG_STRLEN))) {
 434                         ret = -EFAULT;
 435                         goto out;
 436                 }
 437
 438                 if (!valid_arg_len(bprm, len)) {
 439                         ret = -E2BIG;
 440                         goto out;
 441                 }
 442
 443                 /* We're going to work our way backwords. */
 444                 pos = bprm->p;
 445                 str += len;
 446                 bprm->p -= len;
 447
 448                 while (len > 0) {
 449                         int offset, bytes_to_copy;
 450
 451                         if (fatal_signal_pending(current)) {
 452                                 ret = -ERESTARTNOHAND;
 453                                 goto out;
 454                         }
 455                         cond_resched();
 456
 457                         offset = pos % PAGE_SIZE;
 458                         if (offset == 0)
 459                                 offset = PAGE_SIZE;
 460
 461                         bytes_to_copy = offset;
 462                         if (bytes_to_copy > len)
 463                                 bytes_to_copy = len;
 464
 465                         offset -= bytes_to_copy;
 466                         pos -= bytes_to_copy;
 467                         str -= bytes_to_copy;
 468                         len -= bytes_to_copy;
 469
 470                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 471                                 struct page *page;
 472
 473                                 page = get_arg_page(bprm, pos, 1);
 474                                 if (!page) {
 475                                         ret = -E2BIG;
 476                                         goto out;
 477                                 }
 478
 479                                 if (kmapped_page) {
 480                                         flush_kernel_dcache_page(kmapped_page);
 481                                         kunmap(kmapped_page);
 482                                         put_arg_page(kmapped_page);
 483                                 }
 484                                 kmapped_page = page;
 485                                 kaddr = kmap(kmapped_page);
 486                                 kpos = pos & PAGE_MASK;
 487                                 flush_arg_page(bprm, kpos, kmapped_page);
 488                         }
 489                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 490                                 ret = -EFAULT;
 491                                 goto out;
 492                         }
 493                 }
 494         }
 495         ret = 0;
 496 out:
 497         if (kmapped_page) {
 498                 flush_kernel_dcache_page(kmapped_page);
 499                 kunmap(kmapped_page);
 500                 put_arg_page(kmapped_page);
 501         }
 502         return ret;
 503 }
 504
 505 /*
 506  * Like copy_strings, but get argv and its values from kernel memory.
 507  */
 508 int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm)
 509 {
 510         int r;
 511         mm_segment_t oldfs = get_fs();
 512         set_fs(KERNEL_DS);
 513         r = copy_strings(argc, (char __user * __user *)argv, bprm);
 514         set_fs(oldfs);
 515         return r;
 516 }
 517 EXPORT_SYMBOL(copy_strings_kernel);
 518
 519 #ifdef CONFIG_MMU
 520
 521 /*
 522  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 523  * the binfmt code determines where the new stack should reside, we shift it to
 524  * its final location.  The process proceeds as follows:
 525  *
 526  * 1) Use shift to calculate the new vma endpoints.
 527  * 2) Extend vma to cover both the old and new ranges.  This ensures the
 528  *    arguments passed to subsequent functions are consistent.
 529  * 3) Move vma's page tables to the new range.
 530  * 4) Free up any cleared pgd range.
 531  * 5) Shrink the vma to cover only the new range.
 532  */
 533 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 534 {
 535         struct mm_struct *mm = vma->vm_mm;
 536         unsigned long old_start = vma->vm_start;
 537         unsigned long old_end = vma->vm_end;
 538         unsigned long length = old_end - old_start;
 539         unsigned long new_start = old_start - shift;
 540         unsigned long new_end = old_end - shift;
 541         struct mmu_gather *tlb;
 542
 543         BUG_ON(new_start > new_end);
 544
 545         /*
 546          * ensure there are no vmas between where we want to go
 547          * and where we are
 548          */
 549         if (vma != find_vma(mm, new_start))
 550                 return -EFAULT;
 551
 552         /*
 553          * cover the whole range: [new_start, old_end)
 554          */
 555         vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);
 556
 557         /*
 558          * move the page tables downwards, on failure we rely on
 559          * process cleanup to remove whatever mess we made.
 560          */
 561         if (length != move_page_tables(vma, old_start,
 562                                        vma, new_start, length))
 563                 return -ENOMEM;
 564
 565         lru_add_drain();
 566         tlb = tlb_gather_mmu(mm, 0);
 567         if (new_end > old_start) {
 568                 /*
 569                  * when the old and new regions overlap clear from new_end.
 570                  */
 571                 free_pgd_range(tlb, new_end, old_end, new_end,
 572                         vma->vm_next ? vma->vm_next->vm_start : 0);
 573         } else {
 574                 /*
 575                  * otherwise, clean from old_start; this is done to not touch
 576                  * the address space in [new_end, old_start) some architectures
 577                  * have constraints on va-space that make this illegal (IA64) -
 578                  * for the others its just a little faster.
 579                  */
 580                 free_pgd_range(tlb, old_start, old_end, new_end,
 581                         vma->vm_next ? vma->vm_next->vm_start : 0);
 582         }
 583         tlb_finish_mmu(tlb, new_end, old_end);
 584
 585         /*
 586          * shrink the vma to just the new range.
 587          */
 588         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 589
 590         return 0;
 591 }
 592
 593 #define EXTRA_STACK_VM_PAGES    20      /* random */
 594
 595 /*
 596  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 597  * the stack is optionally relocated, and some extra space is added.
 598  */
 599 int setup_arg_pages(struct linux_binprm *bprm,
 600                     unsigned long stack_top,
 601                     int executable_stack)
 602 {
 603         unsigned long ret;
 604         unsigned long stack_shift;
 605         struct mm_struct *mm = current->mm;
 606         struct vm_area_struct *vma = bprm->vma;
 607         struct vm_area_struct *prev = NULL;
 608         unsigned long vm_flags;
 609         unsigned long stack_base;
 610         unsigned long stack_size;
 611         unsigned long stack_expand;
 612         unsigned long rlim_stack;
 613
 614 #ifdef CONFIG_STACK_GROWSUP
 615         /* Limit stack size to 1GB */
 616         stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max;
 617         if (stack_base > (1 << 30))
 618                 stack_base = 1 << 30;
 619
 620         /* Make sure we didn't let the argument array grow too large. */
 621         if (vma->vm_end - vma->vm_start > stack_base)
 622                 return -ENOMEM;
 623
 624         stack_base = PAGE_ALIGN(stack_top - stack_base);
 625
 626         stack_shift = vma->vm_start - stack_base;
 627         mm->arg_start = bprm->p - stack_shift;
 628         bprm->p = vma->vm_end - stack_shift;
 629 #else
 630         stack_top = arch_align_stack(stack_top);
 631         stack_top = PAGE_ALIGN(stack_top);
 632
 633         if (unlikely(stack_top < mmap_min_addr) ||
 634             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 635                 return -ENOMEM;
 636
 637         stack_shift = vma->vm_end - stack_top;
 638
 639         bprm->p -= stack_shift;
 640         mm->arg_start = bprm->p;
 641 #endif
 642
 643         if (bprm->loader)
 644                 bprm->loader -= stack_shift;
 645         bprm->exec -= stack_shift;
 646
 647         down_write(&mm->mmap_sem);
 648         vm_flags = VM_STACK_FLAGS;
 649
 650         /*
 651          * Adjust stack execute permissions; explicitly enable for
 652          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 653          * (arch default) otherwise.
 654          */
 655         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 656                 vm_flags |= VM_EXEC;
 657         else if (executable_stack == EXSTACK_DISABLE_X)
 658                 vm_flags &= ~VM_EXEC;
 659         vm_flags |= mm->def_flags;
 660
 661         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 662                         vm_flags);
 663         if (ret)
 664                 goto out_unlock;
 665         BUG_ON(prev != vma);
 666
 667         /* Move stack pages down in memory. */
 668         if (stack_shift) {
 669                 ret = shift_arg_pages(vma, stack_shift);
 670                 if (ret)
 671                         goto out_unlock;
 672         }
 673
 674         stack_expand = EXTRA_STACK_VM_PAGES * PAGE_SIZE;
 675         stack_size = vma->vm_end - vma->vm_start;
 676         /*
 677          * Align this down to a page boundary as expand_stack
 678          * will align it up.
 679          */
 680         rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 681 #ifdef CONFIG_STACK_GROWSUP
 682         if (stack_size + stack_expand > rlim_stack)
 683                 stack_base = vma->vm_start + rlim_stack;
 684         else
 685                 stack_base = vma->vm_end + stack_expand;
 686 #else
 687         if (stack_size + stack_expand > rlim_stack)
 688                 stack_base = vma->vm_end - rlim_stack;
 689         else
 690                 stack_base = vma->vm_start - stack_expand;
 691 #endif
 692         ret = expand_stack(vma, stack_base);
 693         if (ret)
 694                 ret = -EFAULT;
 695
 696 out_unlock:
 697         up_write(&mm->mmap_sem);
 698         return ret;
 699 }
 700 EXPORT_SYMBOL(setup_arg_pages);
 701
 702 #endif /* CONFIG_MMU */
 703
 704 struct file *open_exec(const char *name)
 705 {
 706         struct file *file;
 707         int err;
 708
 709         file = do_filp_open(AT_FDCWD, name,
 710                                 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0,
 711                                 MAY_EXEC | MAY_OPEN);
 712         if (IS_ERR(file))
 713                 goto out;
 714
 715         err = -EACCES;
 716         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
 717                 goto exit;
 718
 719         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 720                 goto exit;
 721
 722         fsnotify_open(file->f_path.dentry);
 723
 724         err = deny_write_access(file);
 725         if (err)
 726                 goto exit;
 727
 728 out:
 729         return file;
 730
 731 exit:
 732         fput(file);
 733         return ERR_PTR(err);
 734 }
 735 EXPORT_SYMBOL(open_exec);
 736
 737 int kernel_read(struct file *file, loff_t offset,
 738                 char *addr, unsigned long count)
 739 {
 740         mm_segment_t old_fs;
 741         loff_t pos = offset;
 742         int result;
 743
 744         old_fs = get_fs();
 745         set_fs(get_ds());
 746         /* The cast to a user pointer is valid due to the set_fs() */
 747         result = vfs_read(file, (void __user *)addr, count, &pos);
 748         set_fs(old_fs);
 749         return result;
 750 }
 751
 752 EXPORT_SYMBOL(kernel_read);
 753
 754 static int exec_mmap(struct mm_struct *mm)
 755 {
 756         struct task_struct *tsk;
 757         struct mm_struct * old_mm, *active_mm;
 758
 759         /* Notify parent that we're no longer interested in the old VM */
 760         tsk = current;
 761         old_mm = current->mm;
 762         mm_release(tsk, old_mm);
 763
 764         if (old_mm) {
 765                 /*
 766                  * Make sure that if there is a core dump in progress
 767                  * for the old mm, we get out and die instead of going
 768                  * through with the exec.  We must hold mmap_sem around
 769                  * checking core_state and changing tsk->mm.
 770                  */
 771                 down_read(&old_mm->mmap_sem);
 772                 if (unlikely(old_mm->core_state)) {
 773                         up_read(&old_mm->mmap_sem);
 774                         return -EINTR;
 775                 }
 776         }
 777         task_lock(tsk);
 778         active_mm = tsk->active_mm;
 779         tsk->mm = mm;
 780         tsk->active_mm = mm;
 781         activate_mm(active_mm, mm);
 782         task_unlock(tsk);
 783         arch_pick_mmap_layout(mm);
 784         if (old_mm) {
 785                 up_read(&old_mm->mmap_sem);
 786                 BUG_ON(active_mm != old_mm);
 787                 mm_update_next_owner(old_mm);
 788                 mmput(old_mm);
 789                 return 0;
 790         }
 791         mmdrop(active_mm);
 792         return 0;
 793 }
 794
 795 /*
 796  * This function makes sure the current process has its own signal table,
 797  * so that flush_signal_handlers can later reset the handlers without
 798  * disturbing other processes.  (Other processes might share the signal
 799  * table via the CLONE_SIGHAND option to clone().)
 800  */
 801 static int de_thread(struct task_struct *tsk)
 802 {
 803         struct signal_struct *sig = tsk->signal;
 804         struct sighand_struct *oldsighand = tsk->sighand;
 805         spinlock_t *lock = &oldsighand->siglock;
 806         int count;
 807
 808         if (thread_group_empty(tsk))
 809                 goto no_thread_group;
 810
 811         /*
 812          * Kill all other threads in the thread group.
 813          */
 814         spin_lock_irq(lock);
 815         if (signal_group_exit(sig)) {
 816                 /*
 817                  * Another group action in progress, just
 818                  * return so that the signal is processed.
 819                  */
 820                 spin_unlock_irq(lock);
 821                 return -EAGAIN;
 822         }
 823         sig->group_exit_task = tsk;
 824         zap_other_threads(tsk);
 825
 826         /* Account for the thread group leader hanging around: */
 827         count = thread_group_leader(tsk) ? 1 : 2;
 828         sig->notify_count = count;
 829         while (atomic_read(&sig->count) > count) {
 830                 __set_current_state(TASK_UNINTERRUPTIBLE);
 831                 spin_unlock_irq(lock);
 832                 schedule();
 833                 spin_lock_irq(lock);
 834         }
 835         spin_unlock_irq(lock);
 836
 837         /*
 838          * At this point all other threads have exited, all we have to
 839          * do is to wait for the thread group leader to become inactive,
 840          * and to assume its PID:
 841          */
 842         if (!thread_group_leader(tsk)) {
 843                 struct task_struct *leader = tsk->group_leader;
 844
 845                 sig->notify_count = -1; /* for exit_notify() */
 846                 for (;;) {
 847                         write_lock_irq(&tasklist_lock);
 848                         if (likely(leader->exit_state))
 849                                 break;
 850                         __set_current_state(TASK_UNINTERRUPTIBLE);
 851                         write_unlock_irq(&tasklist_lock);
 852                         schedule();
 853                 }
 854
 855                 /*
 856                  * The only record we have of the real-time age of a
 857                  * process, regardless of execs it's done, is start_time.
 858                  * All the past CPU time is accumulated in signal_struct
 859                  * from sister threads now dead.  But in this non-leader
 860                  * exec, nothing survives from the original leader thread,
 861                  * whose birth marks the true age of this process now.
 862                  * When we take on its identity by switching to its PID, we
 863                  * also take its birthdate (always earlier than our own).
 864                  */
 865                 tsk->start_time = leader->start_time;
 866
 867                 BUG_ON(!same_thread_group(leader, tsk));
 868                 BUG_ON(has_group_leader_pid(tsk));
 869                 /*
 870                  * An exec() starts a new thread group with the
 871                  * TGID of the previous thread group. Rehash the
 872                  * two threads with a switched PID, and release
 873                  * the former thread group leader:
 874                  */
 875
 876                 /* Become a process group leader with the old leader's pid.
 877                  * The old leader becomes a thread of the this thread group.
 878                  * Note: The old leader also uses this pid until release_task
 879                  *       is called.  Odd but simple and correct.
 880                  */
 881                 detach_pid(tsk, PIDTYPE_PID);
 882                 tsk->pid = leader->pid;
 883                 attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
 884                 transfer_pid(leader, tsk, PIDTYPE_PGID);
 885                 transfer_pid(leader, tsk, PIDTYPE_SID);
 886                 list_replace_rcu(&leader->tasks, &tsk->tasks);
 887
 888                 tsk->group_leader = tsk;
 889                 leader->group_leader = tsk;
 890
 891                 tsk->exit_signal = SIGCHLD;
 892
 893                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 894                 leader->exit_state = EXIT_DEAD;
 895                 write_unlock_irq(&tasklist_lock);
 896
 897                 release_task(leader);
 898         }
 899
 900         sig->group_exit_task = NULL;
 901         sig->notify_count = 0;
 902
 903 no_thread_group:
 904         if (current->mm)
 905                 setmax_mm_hiwater_rss(&sig->maxrss, current->mm);
 906
 907         exit_itimers(sig);
 908         flush_itimer_signals();
 909
 910         if (atomic_read(&oldsighand->count) != 1) {
 911                 struct sighand_struct *newsighand;
 912                 /*
 913                  * This ->sighand is shared with the CLONE_SIGHAND
 914                  * but not CLONE_THREAD task, switch to the new one.
 915                  */
 916                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 917                 if (!newsighand)
 918                         return -ENOMEM;
 919
 920                 atomic_set(&newsighand->count, 1);
 921                 memcpy(newsighand->action, oldsighand->action,
 922                        sizeof(newsighand->action));
 923
 924                 write_lock_irq(&tasklist_lock);
 925                 spin_lock(&oldsighand->siglock);
 926                 rcu_assign_pointer(tsk->sighand, newsighand);
 927                 spin_unlock(&oldsighand->siglock);
 928                 write_unlock_irq(&tasklist_lock);
 929
 930                 __cleanup_sighand(oldsighand);
 931         }
 932
 933         BUG_ON(!thread_group_leader(tsk));
 934         return 0;
 935 }
 936
 937 /*
 938  * These functions flushes out all traces of the currently running executable
 939  * so that a new one can be started
 940  */
 941 static void flush_old_files(struct files_struct * files)
 942 {
 943         long j = -1;
 944         struct fdtable *fdt;
 945
 946         spin_lock(&files->file_lock);
 947         for (;;) {
 948                 unsigned long set, i;
 949
 950                 j++;
 951                 i = j * __NFDBITS;
 952                 fdt = files_fdtable(files);
 953                 if (i >= fdt->max_fds)
 954                         break;
 955                 set = fdt->close_on_exec->fds_bits[j];
 956                 if (!set)
 957                         continue;
 958                 fdt->close_on_exec->fds_bits[j] = 0;
 959                 spin_unlock(&files->file_lock);
 960                 for ( ; set ; i++,set >>= 1) {
 961                         if (set & 1) {
 962                                 sys_close(i);
 963                         }
 964                 }
 965                 spin_lock(&files->file_lock);
 966
 967         }
 968         spin_unlock(&files->file_lock);
 969 }
 970
 971 char *get_task_comm(char *buf, struct task_struct *tsk)
 972 {
 973         /* buf must be at least sizeof(tsk->comm) in size */
 974         task_lock(tsk);
 975         strncpy(buf, tsk->comm, sizeof(tsk->comm));
 976         task_unlock(tsk);
 977         return buf;
 978 }
 979
 980 void set_task_comm(struct task_struct *tsk, char *buf)
 981 {
 982         task_lock(tsk);
 983         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
 984         task_unlock(tsk);
 985         perf_event_comm(tsk);
 986 }
 987
 988 int flush_old_exec(struct linux_binprm * bprm)
 989 {
 990         int retval;
 991
 992         /*
 993          * Make sure we have a private signal table and that
 994          * we are unassociated from the previous thread group.
 995          */
 996         retval = de_thread(current);
 997         if (retval)
 998                 goto out;
 999
1000         set_mm_exe_file(bprm->mm, bprm->file);
1001
1002         /*
1003          * Release all of the old mmap stuff
1004          */
1005         acct_arg_size(bprm, 0);
1006         retval = exec_mmap(bprm->mm);
1007         if (retval)
1008                 goto out;
1009
1010         bprm->mm = NULL;                /* We're using it now */
1011
1012         set_fs(USER_DS);
1013         current->flags &= ~PF_RANDOMIZE;
1014         flush_thread();
1015         current->personality &= ~bprm->per_clear;
1016
1017         return 0;
1018
1019 out:
1020         return retval;
1021 }
1022 EXPORT_SYMBOL(flush_old_exec);
1023
1024 void setup_new_exec(struct linux_binprm * bprm)
1025 {
1026         int i, ch;
1027         char * name;
1028         char tcomm[sizeof(current->comm)];
1029
1030         arch_pick_mmap_layout(current->mm);
1031
1032         /* This is the point of no return */
1033         current->sas_ss_sp = current->sas_ss_size = 0;
1034
1035         if (current_euid() == current_uid() && current_egid() == current_gid())
1036                 set_dumpable(current->mm, 1);
1037         else
1038                 set_dumpable(current->mm, suid_dumpable);
1039
1040         name = bprm->filename;
1041
1042         /* Copies the binary name from after last slash */
1043         for (i=0; (ch = *(name++)) != '\0';) {
1044                 if (ch == '/')
1045                         i = 0; /* overwrite what we wrote */
1046                 else
1047                         if (i < (sizeof(tcomm) - 1))
1048                                 tcomm[i++] = ch;
1049         }
1050         tcomm[i] = '\0';
1051         set_task_comm(current, tcomm);
1052
1053         /* Set the new mm task size. We have to do that late because it may
1054          * depend on TIF_32BIT which is only updated in flush_thread() on
1055          * some architectures like powerpc
1056          */
1057         current->mm->task_size = TASK_SIZE;
1058
1059         /* install the new credentials */
1060         if (bprm->cred->uid != current_euid() ||
1061             bprm->cred->gid != current_egid()) {
1062                 current->pdeath_signal = 0;
1063         } else if (file_permission(bprm->file, MAY_READ) ||
1064                    bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) {
1065                 set_dumpable(current->mm, suid_dumpable);
1066         }
1067
1068         /*
1069          * Flush performance counters when crossing a
1070          * security domain:
1071          */
1072         if (!get_dumpable(current->mm))
1073                 perf_event_exit_task(current);
1074
1075         /* An exec changes our domain. We are no longer part of the thread
1076            group */
1077
1078         current->self_exec_id++;
1079
1080         flush_signal_handlers(current, 0);
1081         flush_old_files(current->files);
1082 }
1083 EXPORT_SYMBOL(setup_new_exec);
1084
1085 /*
1086  * Prepare credentials and lock ->cred_guard_mutex.
1087  * install_exec_creds() commits the new creds and drops the lock.
1088  * Or, if exec fails before, free_bprm() should release ->cred and
1089  * and unlock.
1090  */
1091 int prepare_bprm_creds(struct linux_binprm *bprm)
1092 {
1093         if (mutex_lock_interruptible(&current->cred_guard_mutex))
1094                 return -ERESTARTNOINTR;
1095
1096         bprm->cred = prepare_exec_creds();
1097         if (likely(bprm->cred))
1098                 return 0;
1099
1100         mutex_unlock(&current->cred_guard_mutex);
1101         return -ENOMEM;
1102 }
1103
1104 void free_bprm(struct linux_binprm *bprm)
1105 {
1106         free_arg_pages(bprm);
1107         if (bprm->cred) {
1108                 mutex_unlock(&current->cred_guard_mutex);
1109                 abort_creds(bprm->cred);
1110         }
1111         kfree(bprm);
1112 }
1113
1114 /*
1115  * install the new credentials for this executable
1116  */
1117 void install_exec_creds(struct linux_binprm *bprm)
1118 {
1119         security_bprm_committing_creds(bprm);
1120
1121         commit_creds(bprm->cred);
1122         bprm->cred = NULL;
1123         /*
1124          * cred_guard_mutex must be held at least to this point to prevent
1125          * ptrace_attach() from altering our determination of the task's
1126          * credentials; any time after this it may be unlocked.
1127          */
1128         security_bprm_committed_creds(bprm);
1129         mutex_unlock(&current->cred_guard_mutex);
1130 }
1131 EXPORT_SYMBOL(install_exec_creds);
1132
1133 /*
1134  * determine how safe it is to execute the proposed program
1135  * - the caller must hold current->cred_guard_mutex to protect against
1136  *   PTRACE_ATTACH
1137  */
1138 int check_unsafe_exec(struct linux_binprm *bprm)
1139 {
1140         struct task_struct *p = current, *t;
1141         unsigned n_fs;
1142         int res = 0;
1143
1144         bprm->unsafe = tracehook_unsafe_exec(p);
1145
1146         n_fs = 1;
1147         write_lock(&p->fs->lock);
1148         rcu_read_lock();
1149         for (t = next_thread(p); t != p; t = next_thread(t)) {
1150                 if (t->fs == p->fs)
1151                         n_fs++;
1152         }
1153         rcu_read_unlock();
1154
1155         if (p->fs->users > n_fs) {
1156                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1157         } else {
1158                 res = -EAGAIN;
1159                 if (!p->fs->in_exec) {
1160                         p->fs->in_exec = 1;
1161                         res = 1;
1162                 }
1163         }
1164         write_unlock(&p->fs->lock);
1165
1166         return res;
1167 }
1168
1169 /*
1170  * Fill the binprm structure from the inode.
1171  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1172  *
1173  * This may be called multiple times for binary chains (scripts for example).
1174  */
1175 int prepare_binprm(struct linux_binprm *bprm)
1176 {
1177         umode_t mode;
1178         struct inode * inode = bprm->file->f_path.dentry->d_inode;
1179         int retval;
1180
1181         mode = inode->i_mode;
1182         if (bprm->file->f_op == NULL)
1183                 return -EACCES;
1184
1185         /* clear any previous set[ug]id data from a previous binary */
1186         bprm->cred->euid = current_euid();
1187         bprm->cred->egid = current_egid();
1188
1189         if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1190                 /* Set-uid? */
1191                 if (mode & S_ISUID) {
1192                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1193                         bprm->cred->euid = inode->i_uid;
1194                 }
1195
1196                 /* Set-gid? */
1197                 /*
1198                  * If setgid is set but no group execute bit then this
1199                  * is a candidate for mandatory locking, not a setgid
1200                  * executable.
1201                  */
1202                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1203                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1204                         bprm->cred->egid = inode->i_gid;
1205                 }
1206         }
1207
1208         /* fill in binprm security blob */
1209         retval = security_bprm_set_creds(bprm);
1210         if (retval)
1211                 return retval;
1212         bprm->cred_prepared = 1;
1213
1214         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1215         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1216 }
1217
1218 EXPORT_SYMBOL(prepare_binprm);
1219
1220 /*
1221  * Arguments are '\0' separated strings found at the location bprm->p
1222  * points to; chop off the first by relocating brpm->p to right after
1223  * the first '\0' encountered.
1224  */
1225 int remove_arg_zero(struct linux_binprm *bprm)
1226 {
1227         int ret = 0;
1228         unsigned long offset;
1229         char *kaddr;
1230         struct page *page;
1231
1232         if (!bprm->argc)
1233                 return 0;
1234
1235         do {
1236                 offset = bprm->p & ~PAGE_MASK;
1237                 page = get_arg_page(bprm, bprm->p, 0);
1238                 if (!page) {
1239                         ret = -EFAULT;
1240                         goto out;
1241                 }
1242                 kaddr = kmap_atomic(page, KM_USER0);
1243
1244                 for (; offset < PAGE_SIZE && kaddr[offset];
1245                                 offset++, bprm->p++)
1246                         ;
1247
1248                 kunmap_atomic(kaddr, KM_USER0);
1249                 put_arg_page(page);
1250
1251                 if (offset == PAGE_SIZE)
1252                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1253         } while (offset == PAGE_SIZE);
1254
1255         bprm->p++;
1256         bprm->argc--;
1257         ret = 0;
1258
1259 out:
1260         return ret;
1261 }
1262 EXPORT_SYMBOL(remove_arg_zero);
1263
1264 /*
1265  * cycle the list of binary formats handler, until one recognizes the image
1266  */
1267 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1268 {
1269         unsigned int depth = bprm->recursion_depth;
1270         int try,retval;
1271         struct linux_binfmt *fmt;
1272
1273         retval = security_bprm_check(bprm);
1274         if (retval)
1275                 return retval;
1276         retval = ima_bprm_check(bprm);
1277         if (retval)
1278                 return retval;
1279
1280         retval = audit_bprm(bprm);
1281         if (retval)
1282                 return retval;
1283
1284         retval = -ENOENT;
1285         for (try=0; try<2; try++) {
1286                 read_lock(&binfmt_lock);
1287                 list_for_each_entry(fmt, &formats, lh) {
1288                         int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1289                         if (!fn)
1290                                 continue;
1291                         if (!try_module_get(fmt->module))
1292                                 continue;
1293                         read_unlock(&binfmt_lock);
1294                         retval = fn(bprm, regs);
1295                         /*
1296                          * Restore the depth counter to its starting value
1297                          * in this call, so we don't have to rely on every
1298                          * load_binary function to restore it on return.
1299                          */
1300                         bprm->recursion_depth = depth;
1301                         if (retval >= 0) {
1302                                 if (depth == 0)
1303                                         tracehook_report_exec(fmt, bprm, regs);
1304                                 put_binfmt(fmt);
1305                                 allow_write_access(bprm->file);
1306                                 if (bprm->file)
1307                                         fput(bprm->file);
1308                                 bprm->file = NULL;
1309                                 current->did_exec = 1;
1310                                 proc_exec_connector(current);
1311                                 return retval;
1312                         }
1313                         read_lock(&binfmt_lock);
1314                         put_binfmt(fmt);
1315                         if (retval != -ENOEXEC || bprm->mm == NULL)
1316                                 break;
1317                         if (!bprm->file) {
1318                                 read_unlock(&binfmt_lock);
1319                                 return retval;
1320                         }
1321                 }
1322                 read_unlock(&binfmt_lock);
1323                 if (retval != -ENOEXEC || bprm->mm == NULL) {
1324                         break;
1325 #ifdef CONFIG_MODULES
1326                 } else {
1327 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1328                         if (printable(bprm->buf[0]) &&
1329                             printable(bprm->buf[1]) &&
1330                             printable(bprm->buf[2]) &&
1331                             printable(bprm->buf[3]))
1332                                 break; /* -ENOEXEC */
1333                         request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1334 #endif
1335                 }
1336         }
1337         return retval;
1338 }
1339
1340 EXPORT_SYMBOL(search_binary_handler);
1341
1342 /*
1343  * sys_execve() executes a new program.
1344  */
1345 int do_execve(char * filename,
1346         char __user *__user *argv,
1347         char __user *__user *envp,
1348         struct pt_regs * regs)
1349 {
1350         struct linux_binprm *bprm;
1351         struct file *file;
1352         struct files_struct *displaced;
1353         bool clear_in_exec;
1354         int retval;
1355
1356         retval = unshare_files(&displaced);
1357         if (retval)
1358                 goto out_ret;
1359
1360         retval = -ENOMEM;
1361         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1362         if (!bprm)
1363                 goto out_files;
1364
1365         retval = prepare_bprm_creds(bprm);
1366         if (retval)
1367                 goto out_free;
1368
1369         retval = check_unsafe_exec(bprm);
1370         if (retval < 0)
1371                 goto out_free;
1372         clear_in_exec = retval;
1373         current->in_execve = 1;
1374
1375         file = open_exec(filename);
1376         retval = PTR_ERR(file);
1377         if (IS_ERR(file))
1378                 goto out_unmark;
1379
1380         sched_exec();
1381
1382         bprm->file = file;
1383         bprm->filename = filename;
1384         bprm->interp = filename;
1385
1386         retval = bprm_mm_init(bprm);
1387         if (retval)
1388                 goto out_file;
1389
1390         bprm->argc = count(argv, MAX_ARG_STRINGS);
1391         if ((retval = bprm->argc) < 0)
1392                 goto out;
1393
1394         bprm->envc = count(envp, MAX_ARG_STRINGS);
1395         if ((retval = bprm->envc) < 0)
1396                 goto out;
1397
1398         retval = prepare_binprm(bprm);
1399         if (retval < 0)
1400                 goto out;
1401
1402         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1403         if (retval < 0)
1404                 goto out;
1405
1406         bprm->exec = bprm->p;
1407         retval = copy_strings(bprm->envc, envp, bprm);
1408         if (retval < 0)
1409                 goto out;
1410
1411         retval = copy_strings(bprm->argc, argv, bprm);
1412         if (retval < 0)
1413                 goto out;
1414
1415         current->flags &= ~PF_KTHREAD;
1416         retval = search_binary_handler(bprm,regs);
1417         if (retval < 0)
1418                 goto out;
1419
1420         /* execve succeeded */
1421         current->fs->in_exec = 0;
1422         current->in_execve = 0;
1423         acct_update_integrals(current);
1424         free_bprm(bprm);
1425         if (displaced)
1426                 put_files_struct(displaced);
1427         return retval;
1428
1429 out:
1430         if (bprm->mm) {
1431                 acct_arg_size(bprm, 0);
1432                 mmput(bprm->mm);
1433         }
1434
1435 out_file:
1436         if (bprm->file) {
1437                 allow_write_access(bprm->file);
1438                 fput(bprm->file);
1439         }
1440
1441 out_unmark:
1442         if (clear_in_exec)
1443                 current->fs->in_exec = 0;
1444         current->in_execve = 0;
1445
1446 out_free:
1447         free_bprm(bprm);
1448
1449 out_files:
1450         if (displaced)
1451                 reset_files_struct(displaced);
1452 out_ret:
1453         return retval;
1454 }
1455
1456 void set_binfmt(struct linux_binfmt *new)
1457 {
1458         struct mm_struct *mm = current->mm;
1459
1460         if (mm->binfmt)
1461                 module_put(mm->binfmt->module);
1462
1463         mm->binfmt = new;
1464         if (new)
1465                 __module_get(new->module);
1466 }
1467
1468 EXPORT_SYMBOL(set_binfmt);
1469
1470 /* format_corename will inspect the pattern parameter, and output a
1471  * name into corename, which must have space for at least
1472  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1473  */
1474 static int format_corename(char *corename, long signr)
1475 {
1476         const struct cred *cred = current_cred();
1477         const char *pat_ptr = core_pattern;
1478         int ispipe = (*pat_ptr == '|');
1479         char *out_ptr = corename;
1480         char *const out_end = corename + CORENAME_MAX_SIZE;
1481         int rc;
1482         int pid_in_pattern = 0;
1483
1484         /* Repeat as long as we have more pattern to process and more output
1485            space */
1486         while (*pat_ptr) {
1487                 if (*pat_ptr != '%') {
1488                         if (out_ptr == out_end)
1489                                 goto out;
1490                         *out_ptr++ = *pat_ptr++;
1491                 } else {
1492                         switch (*++pat_ptr) {
1493                         case 0:
1494                                 goto out;
1495                         /* Double percent, output one percent */
1496                         case '%':
1497                                 if (out_ptr == out_end)
1498                                         goto out;
1499                                 *out_ptr++ = '%';
1500                                 break;
1501                         /* pid */
1502                         case 'p':
1503                                 pid_in_pattern = 1;
1504                                 rc = snprintf(out_ptr, out_end - out_ptr,
1505                                               "%d", task_tgid_vnr(current));
1506                                 if (rc > out_end - out_ptr)
1507                                         goto out;
1508                                 out_ptr += rc;
1509                                 break;
1510                         /* uid */
1511                         case 'u':
1512                                 rc = snprintf(out_ptr, out_end - out_ptr,
1513                                               "%d", cred->uid);
1514                                 if (rc > out_end - out_ptr)
1515                                         goto out;
1516                                 out_ptr += rc;
1517                                 break;
1518                         /* gid */
1519                         case 'g':
1520                                 rc = snprintf(out_ptr, out_end - out_ptr,
1521                                               "%d", cred->gid);
1522                                 if (rc > out_end - out_ptr)
1523                                         goto out;
1524                                 out_ptr += rc;
1525                                 break;
1526                         /* signal that caused the coredump */
1527                         case 's':
1528                                 rc = snprintf(out_ptr, out_end - out_ptr,
1529                                               "%ld", signr);
1530                                 if (rc > out_end - out_ptr)
1531                                         goto out;
1532                                 out_ptr += rc;
1533                                 break;
1534                         /* UNIX time of coredump */
1535                         case 't': {
1536                                 struct timeval tv;
1537                                 do_gettimeofday(&tv);
1538                                 rc = snprintf(out_ptr, out_end - out_ptr,
1539                                               "%lu", tv.tv_sec);
1540                                 if (rc > out_end - out_ptr)
1541                                         goto out;
1542                                 out_ptr += rc;
1543                                 break;
1544                         }
1545                         /* hostname */
1546                         case 'h':
1547                                 down_read(&uts_sem);
1548                                 rc = snprintf(out_ptr, out_end - out_ptr,
1549                                               "%s", utsname()->nodename);
1550                                 up_read(&uts_sem);
1551                                 if (rc > out_end - out_ptr)
1552                                         goto out;
1553                                 out_ptr += rc;
1554                                 break;
1555                         /* executable */
1556                         case 'e':
1557                                 rc = snprintf(out_ptr, out_end - out_ptr,
1558                                               "%s", current->comm);
1559                                 if (rc > out_end - out_ptr)
1560                                         goto out;
1561                                 out_ptr += rc;
1562                                 break;
1563                         /* core limit size */
1564                         case 'c':
1565                                 rc = snprintf(out_ptr, out_end - out_ptr,
1566                                               "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur);
1567                                 if (rc > out_end - out_ptr)
1568                                         goto out;
1569                                 out_ptr += rc;
1570                                 break;
1571                         default:
1572                                 break;
1573                         }
1574                         ++pat_ptr;
1575                 }
1576         }
1577         /* Backward compatibility with core_uses_pid:
1578          *
1579          * If core_pattern does not include a %p (as is the default)
1580          * and core_uses_pid is set, then .%pid will be appended to
1581          * the filename. Do not do this for piped commands. */
1582         if (!ispipe && !pid_in_pattern && core_uses_pid) {
1583                 rc = snprintf(out_ptr, out_end - out_ptr,
1584                               ".%d", task_tgid_vnr(current));
1585                 if (rc > out_end - out_ptr)
1586                         goto out;
1587                 out_ptr += rc;
1588         }
1589 out:
1590         *out_ptr = 0;
1591         return ispipe;
1592 }
1593
1594 static int zap_process(struct task_struct *start)
1595 {
1596         struct task_struct *t;
1597         int nr = 0;
1598
1599         start->signal->flags = SIGNAL_GROUP_EXIT;
1600         start->signal->group_stop_count = 0;
1601
1602         t = start;
1603         do {
1604                 if (t != current && t->mm) {
1605                         sigaddset(&t->pending.signal, SIGKILL);
1606                         signal_wake_up(t, 1);
1607                         nr++;
1608                 }
1609         } while_each_thread(start, t);
1610
1611         return nr;
1612 }
1613
1614 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1615                                 struct core_state *core_state, int exit_code)
1616 {
1617         struct task_struct *g, *p;
1618         unsigned long flags;
1619         int nr = -EAGAIN;
1620
1621         spin_lock_irq(&tsk->sighand->siglock);
1622         if (!signal_group_exit(tsk->signal)) {
1623                 mm->core_state = core_state;
1624                 tsk->signal->group_exit_code = exit_code;
1625                 nr = zap_process(tsk);
1626         }
1627         spin_unlock_irq(&tsk->sighand->siglock);
1628         if (unlikely(nr < 0))
1629                 return nr;
1630
1631         if (atomic_read(&mm->mm_users) == nr + 1)
1632                 goto done;
1633         /*
1634          * We should find and kill all tasks which use this mm, and we should
1635          * count them correctly into ->nr_threads. We don't take tasklist
1636          * lock, but this is safe wrt:
1637          *
1638          * fork:
1639          *      None of sub-threads can fork after zap_process(leader). All
1640          *      processes which were created before this point should be
1641          *      visible to zap_threads() because copy_process() adds the new
1642          *      process to the tail of init_task.tasks list, and lock/unlock
1643          *      of ->siglock provides a memory barrier.
1644          *
1645          * do_exit:
1646          *      The caller holds mm->mmap_sem. This means that the task which
1647          *      uses this mm can't pass exit_mm(), so it can't exit or clear
1648          *      its ->mm.
1649          *
1650          * de_thread:
1651          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
1652          *      we must see either old or new leader, this does not matter.
1653          *      However, it can change p->sighand, so lock_task_sighand(p)
1654          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
1655          *      it can't fail.
1656          *
1657          *      Note also that "g" can be the old leader with ->mm == NULL
1658          *      and already unhashed and thus removed from ->thread_group.
1659          *      This is OK, __unhash_process()->list_del_rcu() does not
1660          *      clear the ->next pointer, we will find the new leader via
1661          *      next_thread().
1662          */
1663         rcu_read_lock();
1664         for_each_process(g) {
1665                 if (g == tsk->group_leader)
1666                         continue;
1667                 if (g->flags & PF_KTHREAD)
1668                         continue;
1669                 p = g;
1670                 do {
1671                         if (p->mm) {
1672                                 if (unlikely(p->mm == mm)) {
1673                                         lock_task_sighand(p, &flags);
1674                                         nr += zap_process(p);
1675                                         unlock_task_sighand(p, &flags);
1676                                 }
1677                                 break;
1678                         }
1679                 } while_each_thread(g, p);
1680         }
1681         rcu_read_unlock();
1682 done:
1683         atomic_set(&core_state->nr_threads, nr);
1684         return nr;
1685 }
1686
1687 static int coredump_wait(int exit_code, struct core_state *core_state)
1688 {
1689         struct task_struct *tsk = current;
1690         struct mm_struct *mm = tsk->mm;
1691         struct completion *vfork_done;
1692         int core_waiters;
1693
1694         init_completion(&core_state->startup);
1695         core_state->dumper.task = tsk;
1696         core_state->dumper.next = NULL;
1697         core_waiters = zap_threads(tsk, mm, core_state, exit_code);
1698         up_write(&mm->mmap_sem);
1699
1700         if (unlikely(core_waiters < 0))
1701                 goto fail;
1702
1703         /*
1704          * Make sure nobody is waiting for us to release the VM,
1705          * otherwise we can deadlock when we wait on each other
1706          */
1707         vfork_done = tsk->vfork_done;
1708         if (vfork_done) {
1709                 tsk->vfork_done = NULL;
1710                 complete(vfork_done);
1711         }
1712
1713         if (core_waiters)
1714                 wait_for_completion(&core_state->startup);
1715 fail:
1716         return core_waiters;
1717 }
1718
1719 static void coredump_finish(struct mm_struct *mm)
1720 {
1721         struct core_thread *curr, *next;
1722         struct task_struct *task;
1723
1724         next = mm->core_state->dumper.next;
1725         while ((curr = next) != NULL) {
1726                 next = curr->next;
1727                 task = curr->task;
1728                 /*
1729                  * see exit_mm(), curr->task must not see
1730                  * ->task == NULL before we read ->next.
1731                  */
1732                 smp_mb();
1733                 curr->task = NULL;
1734                 wake_up_process(task);
1735         }
1736
1737         mm->core_state = NULL;
1738 }
1739
1740 /*
1741  * set_dumpable converts traditional three-value dumpable to two flags and
1742  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1743  * these bits are not changed atomically.  So get_dumpable can observe the
1744  * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1745  * return either old dumpable or new one by paying attention to the order of
1746  * modifying the bits.
1747  *
1748  * dumpable |   mm->flags (binary)
1749  * old  new | initial interim  final
1750  * ---------+-----------------------
1751  *  0    1  |   00      01      01
1752  *  0    2  |   00      10(*)   11
1753  *  1    0  |   01      00      00
1754  *  1    2  |   01      11      11
1755  *  2    0  |   11      10(*)   00
1756  *  2    1  |   11      11      01
1757  *
1758  * (*) get_dumpable regards interim value of 10 as 11.
1759  */
1760 void set_dumpable(struct mm_struct *mm, int value)
1761 {
1762         switch (value) {
1763         case 0:
1764                 clear_bit(MMF_DUMPABLE, &mm->flags);
1765                 smp_wmb();
1766                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1767                 break;
1768         case 1:
1769                 set_bit(MMF_DUMPABLE, &mm->flags);
1770                 smp_wmb();
1771                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1772                 break;
1773         case 2:
1774                 set_bit(MMF_DUMP_SECURELY, &mm->flags);
1775                 smp_wmb();
1776                 set_bit(MMF_DUMPABLE, &mm->flags);
1777                 break;
1778         }
1779 }
1780
1781 int get_dumpable(struct mm_struct *mm)
1782 {
1783         int ret;
1784
1785         ret = mm->flags & 0x3;
1786         return (ret >= 2) ? 2 : ret;
1787 }
1788
1789 static void wait_for_dump_helpers(struct file *file)
1790 {
1791         struct pipe_inode_info *pipe;
1792
1793         pipe = file->f_path.dentry->d_inode->i_pipe;
1794
1795         pipe_lock(pipe);
1796         pipe->readers++;
1797         pipe->writers--;
1798
1799         while ((pipe->readers > 1) && (!signal_pending(current))) {
1800                 wake_up_interruptible_sync(&pipe->wait);
1801                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
1802                 pipe_wait(pipe);
1803         }
1804
1805         pipe->readers--;
1806         pipe->writers++;
1807         pipe_unlock(pipe);
1808
1809 }
1810
1811
1812 void do_coredump(long signr, int exit_code, struct pt_regs *regs)
1813 {
1814         struct core_state core_state;
1815         char corename[CORENAME_MAX_SIZE + 1];
1816         struct mm_struct *mm = current->mm;
1817         struct linux_binfmt * binfmt;
1818         struct inode * inode;
1819         struct file * file;
1820         const struct cred *old_cred;
1821         struct cred *cred;
1822         int retval = 0;
1823         int flag = 0;
1824         int ispipe = 0;
1825         unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
1826         char **helper_argv = NULL;
1827         int helper_argc = 0;
1828         int dump_count = 0;
1829         static atomic_t core_dump_count = ATOMIC_INIT(0);
1830
1831         audit_core_dumps(signr);
1832
1833         binfmt = mm->binfmt;
1834         if (!binfmt || !binfmt->core_dump)
1835                 goto fail;
1836
1837         cred = prepare_creds();
1838         if (!cred) {
1839                 retval = -ENOMEM;
1840                 goto fail;
1841         }
1842
1843         down_write(&mm->mmap_sem);
1844         /*
1845          * If another thread got here first, or we are not dumpable, bail out.
1846          */
1847         if (mm->core_state || !get_dumpable(mm)) {
1848                 up_write(&mm->mmap_sem);
1849                 put_cred(cred);
1850                 goto fail;
1851         }
1852
1853         /*
1854          *      We cannot trust fsuid as being the "true" uid of the
1855          *      process nor do we know its entire history. We only know it
1856          *      was tainted so we dump it as root in mode 2.
1857          */
1858         if (get_dumpable(mm) == 2) {    /* Setuid core dump mode */
1859                 flag = O_EXCL;          /* Stop rewrite attacks */
1860                 cred->fsuid = 0;        /* Dump root private */
1861         }
1862
1863         retval = coredump_wait(exit_code, &core_state);
1864         if (retval < 0) {
1865                 put_cred(cred);
1866                 goto fail;
1867         }
1868
1869         old_cred = override_creds(cred);
1870
1871         /*
1872          * Clear any false indication of pending signals that might
1873          * be seen by the filesystem code called to write the core file.
1874          */
1875         clear_thread_flag(TIF_SIGPENDING);
1876
1877         /*
1878          * lock_kernel() because format_corename() is controlled by sysctl, which
1879          * uses lock_kernel()
1880          */
1881         lock_kernel();
1882         ispipe = format_corename(corename, signr);
1883         unlock_kernel();
1884
1885         if ((!ispipe) && (core_limit < binfmt->min_coredump))
1886                 goto fail_unlock;
1887
1888         if (ispipe) {
1889                 if (core_limit == 0) {
1890                         /*
1891                          * Normally core limits are irrelevant to pipes, since
1892                          * we're not writing to the file system, but we use
1893                          * core_limit of 0 here as a speacial value. Any
1894                          * non-zero limit gets set to RLIM_INFINITY below, but
1895                          * a limit of 0 skips the dump.  This is a consistent
1896                          * way to catch recursive crashes.  We can still crash
1897                          * if the core_pattern binary sets RLIM_CORE =  !0
1898                          * but it runs as root, and can do lots of stupid things
1899                          * Note that we use task_tgid_vnr here to grab the pid
1900                          * of the process group leader.  That way we get the
1901                          * right pid if a thread in a multi-threaded
1902                          * core_pattern process dies.
1903                          */
1904                         printk(KERN_WARNING
1905                                 "Process %d(%s) has RLIMIT_CORE set to 0\n",
1906                                 task_tgid_vnr(current), current->comm);
1907                         printk(KERN_WARNING "Aborting core\n");
1908                         goto fail_unlock;
1909                 }
1910
1911                 dump_count = atomic_inc_return(&core_dump_count);
1912                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
1913                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
1914                                task_tgid_vnr(current), current->comm);
1915                         printk(KERN_WARNING "Skipping core dump\n");
1916                         goto fail_dropcount;
1917                 }
1918
1919                 helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc);
1920                 if (!helper_argv) {
1921                         printk(KERN_WARNING "%s failed to allocate memory\n",
1922                                __func__);
1923                         goto fail_dropcount;
1924                 }
1925
1926                 core_limit = RLIM_INFINITY;
1927
1928                 /* SIGPIPE can happen, but it's just never processed */
1929                 if (call_usermodehelper_pipe(helper_argv[0], helper_argv, NULL,
1930                                 &file)) {
1931                         printk(KERN_INFO "Core dump to %s pipe failed\n",
1932                                corename);
1933                         goto fail_dropcount;
1934                 }
1935         } else
1936                 file = filp_open(corename,
1937                                  O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
1938                                  0600);
1939         if (IS_ERR(file))
1940                 goto fail_dropcount;
1941         inode = file->f_path.dentry->d_inode;
1942         if (inode->i_nlink > 1)
1943                 goto close_fail;        /* multiple links - don't dump */
1944         if (!ispipe && d_unhashed(file->f_path.dentry))
1945                 goto close_fail;
1946
1947         /* AK: actually i see no reason to not allow this for named pipes etc.,
1948            but keep the previous behaviour for now. */
1949         if (!ispipe && !S_ISREG(inode->i_mode))
1950                 goto close_fail;
1951         /*
1952          * Dont allow local users get cute and trick others to coredump
1953          * into their pre-created files:
1954          * Note, this is not relevant for pipes
1955          */
1956         if (!ispipe && (inode->i_uid != current_fsuid()))
1957                 goto close_fail;
1958         if (!file->f_op)
1959                 goto close_fail;
1960         if (!file->f_op->write)
1961                 goto close_fail;
1962         if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0)
1963                 goto close_fail;
1964
1965         retval = binfmt->core_dump(signr, regs, file, core_limit);
1966
1967         if (retval)
1968                 current->signal->group_exit_code |= 0x80;
1969 close_fail:
1970         if (ispipe && core_pipe_limit)
1971                 wait_for_dump_helpers(file);
1972         filp_close(file, NULL);
1973 fail_dropcount:
1974         if (dump_count)
1975                 atomic_dec(&core_dump_count);
1976 fail_unlock:
1977         if (helper_argv)
1978                 argv_free(helper_argv);
1979
1980         revert_creds(old_cred);
1981         put_cred(cred);
1982         coredump_finish(mm);
1983 fail:
1984         return;
1985 }