git.oblomov.eu Git - linux-2.6/blob - 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/highmem.h>
  37 #include <linux/spinlock.h>
  38 #include <linux/key.h>
  39 #include <linux/personality.h>
  40 #include <linux/binfmts.h>
  41 #include <linux/utsname.h>
  42 #include <linux/pid_namespace.h>
  43 #include <linux/module.h>
  44 #include <linux/namei.h>
  45 #include <linux/proc_fs.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
  56 #include <asm/uaccess.h>
  57 #include <asm/mmu_context.h>
  58 #include <asm/tlb.h>
  59 #include "internal.h"
  60
  61 int core_uses_pid;
  62 char core_pattern[CORENAME_MAX_SIZE] = "core";
  63 int suid_dumpable = 0;
  64
  65 /* The maximal length of core_pattern is also specified in sysctl.c */
  66
  67 static LIST_HEAD(formats);
  68 static DEFINE_RWLOCK(binfmt_lock);
  69
  70 int register_binfmt(struct linux_binfmt * fmt)
  71 {
  72         if (!fmt)
  73                 return -EINVAL;
  74         write_lock(&binfmt_lock);
  75         list_add(&fmt->lh, &formats);
  76         write_unlock(&binfmt_lock);
  77         return 0;
  78 }
  79
  80 EXPORT_SYMBOL(register_binfmt);
  81
  82 void unregister_binfmt(struct linux_binfmt * fmt)
  83 {
  84         write_lock(&binfmt_lock);
  85         list_del(&fmt->lh);
  86         write_unlock(&binfmt_lock);
  87 }
  88
  89 EXPORT_SYMBOL(unregister_binfmt);
  90
  91 static inline void put_binfmt(struct linux_binfmt * fmt)
  92 {
  93         module_put(fmt->module);
  94 }
  95
  96 /*
  97  * Note that a shared library must be both readable and executable due to
  98  * security reasons.
  99  *
 100  * Also note that we take the address to load from from the file itself.
 101  */
 102 asmlinkage long sys_uselib(const char __user * library)
 103 {
 104         struct file *file;
 105         struct nameidata nd;
 106         char *tmp = getname(library);
 107         int error = PTR_ERR(tmp);
 108
 109         if (!IS_ERR(tmp)) {
 110                 error = path_lookup_open(AT_FDCWD, tmp,
 111                                          LOOKUP_FOLLOW, &nd,
 112                                          FMODE_READ|FMODE_EXEC);
 113                 putname(tmp);
 114         }
 115         if (error)
 116                 goto out;
 117
 118         error = -EINVAL;
 119         if (!S_ISREG(nd.path.dentry->d_inode->i_mode))
 120                 goto exit;
 121
 122         error = -EACCES;
 123         if (nd.path.mnt->mnt_flags & MNT_NOEXEC)
 124                 goto exit;
 125
 126         error = inode_permission(nd.path.dentry->d_inode,
 127                                  MAY_READ | MAY_EXEC | MAY_OPEN);
 128         if (error)
 129                 goto exit;
 130
 131         file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE);
 132         error = PTR_ERR(file);
 133         if (IS_ERR(file))
 134                 goto out;
 135
 136         fsnotify_open(file->f_path.dentry);
 137
 138         error = -ENOEXEC;
 139         if(file->f_op) {
 140                 struct linux_binfmt * fmt;
 141
 142                 read_lock(&binfmt_lock);
 143                 list_for_each_entry(fmt, &formats, lh) {
 144                         if (!fmt->load_shlib)
 145                                 continue;
 146                         if (!try_module_get(fmt->module))
 147                                 continue;
 148                         read_unlock(&binfmt_lock);
 149                         error = fmt->load_shlib(file);
 150                         read_lock(&binfmt_lock);
 151                         put_binfmt(fmt);
 152                         if (error != -ENOEXEC)
 153                                 break;
 154                 }
 155                 read_unlock(&binfmt_lock);
 156         }
 157         fput(file);
 158 out:
 159         return error;
 160 exit:
 161         release_open_intent(&nd);
 162         path_put(&nd.path);
 163         goto out;
 164 }
 165
 166 #ifdef CONFIG_MMU
 167
 168 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 169                 int write)
 170 {
 171         struct page *page;
 172         int ret;
 173
 174 #ifdef CONFIG_STACK_GROWSUP
 175         if (write) {
 176                 ret = expand_stack_downwards(bprm->vma, pos);
 177                 if (ret < 0)
 178                         return NULL;
 179         }
 180 #endif
 181         ret = get_user_pages(current, bprm->mm, pos,
 182                         1, write, 1, &page, NULL);
 183         if (ret <= 0)
 184                 return NULL;
 185
 186         if (write) {
 187                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 188                 struct rlimit *rlim;
 189
 190                 /*
 191                  * We've historically supported up to 32 pages (ARG_MAX)
 192                  * of argument strings even with small stacks
 193                  */
 194                 if (size <= ARG_MAX)
 195                         return page;
 196
 197                 /*
 198                  * Limit to 1/4-th the stack size for the argv+env strings.
 199                  * This ensures that:
 200                  *  - the remaining binfmt code will not run out of stack space,
 201                  *  - the program will have a reasonable amount of stack left
 202                  *    to work from.
 203                  */
 204                 rlim = current->signal->rlim;
 205                 if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
 206                         put_page(page);
 207                         return NULL;
 208                 }
 209         }
 210
 211         return page;
 212 }
 213
 214 static void put_arg_page(struct page *page)
 215 {
 216         put_page(page);
 217 }
 218
 219 static void free_arg_page(struct linux_binprm *bprm, int i)
 220 {
 221 }
 222
 223 static void free_arg_pages(struct linux_binprm *bprm)
 224 {
 225 }
 226
 227 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 228                 struct page *page)
 229 {
 230         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 231 }
 232
 233 static int __bprm_mm_init(struct linux_binprm *bprm)
 234 {
 235         int err = -ENOMEM;
 236         struct vm_area_struct *vma = NULL;
 237         struct mm_struct *mm = bprm->mm;
 238
 239         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 240         if (!vma)
 241                 goto err;
 242
 243         down_write(&mm->mmap_sem);
 244         vma->vm_mm = mm;
 245
 246         /*
 247          * Place the stack at the largest stack address the architecture
 248          * supports. Later, we'll move this to an appropriate place. We don't
 249          * use STACK_TOP because that can depend on attributes which aren't
 250          * configured yet.
 251          */
 252         vma->vm_end = STACK_TOP_MAX;
 253         vma->vm_start = vma->vm_end - PAGE_SIZE;
 254
 255         vma->vm_flags = VM_STACK_FLAGS;
 256         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 257         err = insert_vm_struct(mm, vma);
 258         if (err) {
 259                 up_write(&mm->mmap_sem);
 260                 goto err;
 261         }
 262
 263         mm->stack_vm = mm->total_vm = 1;
 264         up_write(&mm->mmap_sem);
 265
 266         bprm->p = vma->vm_end - sizeof(void *);
 267
 268         return 0;
 269
 270 err:
 271         if (vma) {
 272                 bprm->vma = NULL;
 273                 kmem_cache_free(vm_area_cachep, vma);
 274         }
 275
 276         return err;
 277 }
 278
 279 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 280 {
 281         return len <= MAX_ARG_STRLEN;
 282 }
 283
 284 #else
 285
 286 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 287                 int write)
 288 {
 289         struct page *page;
 290
 291         page = bprm->page[pos / PAGE_SIZE];
 292         if (!page && write) {
 293                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 294                 if (!page)
 295                         return NULL;
 296                 bprm->page[pos / PAGE_SIZE] = page;
 297         }
 298
 299         return page;
 300 }
 301
 302 static void put_arg_page(struct page *page)
 303 {
 304 }
 305
 306 static void free_arg_page(struct linux_binprm *bprm, int i)
 307 {
 308         if (bprm->page[i]) {
 309                 __free_page(bprm->page[i]);
 310                 bprm->page[i] = NULL;
 311         }
 312 }
 313
 314 static void free_arg_pages(struct linux_binprm *bprm)
 315 {
 316         int i;
 317
 318         for (i = 0; i < MAX_ARG_PAGES; i++)
 319                 free_arg_page(bprm, i);
 320 }
 321
 322 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 323                 struct page *page)
 324 {
 325 }
 326
 327 static int __bprm_mm_init(struct linux_binprm *bprm)
 328 {
 329         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 330         return 0;
 331 }
 332
 333 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 334 {
 335         return len <= bprm->p;
 336 }
 337
 338 #endif /* CONFIG_MMU */
 339
 340 /*
 341  * Create a new mm_struct and populate it with a temporary stack
 342  * vm_area_struct.  We don't have enough context at this point to set the stack
 343  * flags, permissions, and offset, so we use temporary values.  We'll update
 344  * them later in setup_arg_pages().
 345  */
 346 int bprm_mm_init(struct linux_binprm *bprm)
 347 {
 348         int err;
 349         struct mm_struct *mm = NULL;
 350
 351         bprm->mm = mm = mm_alloc();
 352         err = -ENOMEM;
 353         if (!mm)
 354                 goto err;
 355
 356         err = init_new_context(current, mm);
 357         if (err)
 358                 goto err;
 359
 360         err = __bprm_mm_init(bprm);
 361         if (err)
 362                 goto err;
 363
 364         return 0;
 365
 366 err:
 367         if (mm) {
 368                 bprm->mm = NULL;
 369                 mmdrop(mm);
 370         }
 371
 372         return err;
 373 }
 374
 375 /*
 376  * count() counts the number of strings in array ARGV.
 377  */
 378 static int count(char __user * __user * argv, int max)
 379 {
 380         int i = 0;
 381
 382         if (argv != NULL) {
 383                 for (;;) {
 384                         char __user * p;
 385
 386                         if (get_user(p, argv))
 387                                 return -EFAULT;
 388                         if (!p)
 389                                 break;
 390                         argv++;
 391                         if (i++ >= max)
 392                                 return -E2BIG;
 393                         cond_resched();
 394                 }
 395         }
 396         return i;
 397 }
 398
 399 /*
 400  * 'copy_strings()' copies argument/environment strings from the old
 401  * processes's memory to the new process's stack.  The call to get_user_pages()
 402  * ensures the destination page is created and not swapped out.
 403  */
 404 static int copy_strings(int argc, char __user * __user * argv,
 405                         struct linux_binprm *bprm)
 406 {
 407         struct page *kmapped_page = NULL;
 408         char *kaddr = NULL;
 409         unsigned long kpos = 0;
 410         int ret;
 411
 412         while (argc-- > 0) {
 413                 char __user *str;
 414                 int len;
 415                 unsigned long pos;
 416
 417                 if (get_user(str, argv+argc) ||
 418                                 !(len = strnlen_user(str, MAX_ARG_STRLEN))) {
 419                         ret = -EFAULT;
 420                         goto out;
 421                 }
 422
 423                 if (!valid_arg_len(bprm, len)) {
 424                         ret = -E2BIG;
 425                         goto out;
 426                 }
 427
 428                 /* We're going to work our way backwords. */
 429                 pos = bprm->p;
 430                 str += len;
 431                 bprm->p -= len;
 432
 433                 while (len > 0) {
 434                         int offset, bytes_to_copy;
 435
 436                         offset = pos % PAGE_SIZE;
 437                         if (offset == 0)
 438                                 offset = PAGE_SIZE;
 439
 440                         bytes_to_copy = offset;
 441                         if (bytes_to_copy > len)
 442                                 bytes_to_copy = len;
 443
 444                         offset -= bytes_to_copy;
 445                         pos -= bytes_to_copy;
 446                         str -= bytes_to_copy;
 447                         len -= bytes_to_copy;
 448
 449                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 450                                 struct page *page;
 451
 452                                 page = get_arg_page(bprm, pos, 1);
 453                                 if (!page) {
 454                                         ret = -E2BIG;
 455                                         goto out;
 456                                 }
 457
 458                                 if (kmapped_page) {
 459                                         flush_kernel_dcache_page(kmapped_page);
 460                                         kunmap(kmapped_page);
 461                                         put_arg_page(kmapped_page);
 462                                 }
 463                                 kmapped_page = page;
 464                                 kaddr = kmap(kmapped_page);
 465                                 kpos = pos & PAGE_MASK;
 466                                 flush_arg_page(bprm, kpos, kmapped_page);
 467                         }
 468                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 469                                 ret = -EFAULT;
 470                                 goto out;
 471                         }
 472                 }
 473         }
 474         ret = 0;
 475 out:
 476         if (kmapped_page) {
 477                 flush_kernel_dcache_page(kmapped_page);
 478                 kunmap(kmapped_page);
 479                 put_arg_page(kmapped_page);
 480         }
 481         return ret;
 482 }
 483
 484 /*
 485  * Like copy_strings, but get argv and its values from kernel memory.
 486  */
 487 int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm)
 488 {
 489         int r;
 490         mm_segment_t oldfs = get_fs();
 491         set_fs(KERNEL_DS);
 492         r = copy_strings(argc, (char __user * __user *)argv, bprm);
 493         set_fs(oldfs);
 494         return r;
 495 }
 496 EXPORT_SYMBOL(copy_strings_kernel);
 497
 498 #ifdef CONFIG_MMU
 499
 500 /*
 501  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 502  * the binfmt code determines where the new stack should reside, we shift it to
 503  * its final location.  The process proceeds as follows:
 504  *
 505  * 1) Use shift to calculate the new vma endpoints.
 506  * 2) Extend vma to cover both the old and new ranges.  This ensures the
 507  *    arguments passed to subsequent functions are consistent.
 508  * 3) Move vma's page tables to the new range.
 509  * 4) Free up any cleared pgd range.
 510  * 5) Shrink the vma to cover only the new range.
 511  */
 512 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 513 {
 514         struct mm_struct *mm = vma->vm_mm;
 515         unsigned long old_start = vma->vm_start;
 516         unsigned long old_end = vma->vm_end;
 517         unsigned long length = old_end - old_start;
 518         unsigned long new_start = old_start - shift;
 519         unsigned long new_end = old_end - shift;
 520         struct mmu_gather *tlb;
 521
 522         BUG_ON(new_start > new_end);
 523
 524         /*
 525          * ensure there are no vmas between where we want to go
 526          * and where we are
 527          */
 528         if (vma != find_vma(mm, new_start))
 529                 return -EFAULT;
 530
 531         /*
 532          * cover the whole range: [new_start, old_end)
 533          */
 534         vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);
 535
 536         /*
 537          * move the page tables downwards, on failure we rely on
 538          * process cleanup to remove whatever mess we made.
 539          */
 540         if (length != move_page_tables(vma, old_start,
 541                                        vma, new_start, length))
 542                 return -ENOMEM;
 543
 544         lru_add_drain();
 545         tlb = tlb_gather_mmu(mm, 0);
 546         if (new_end > old_start) {
 547                 /*
 548                  * when the old and new regions overlap clear from new_end.
 549                  */
 550                 free_pgd_range(tlb, new_end, old_end, new_end,
 551                         vma->vm_next ? vma->vm_next->vm_start : 0);
 552         } else {
 553                 /*
 554                  * otherwise, clean from old_start; this is done to not touch
 555                  * the address space in [new_end, old_start) some architectures
 556                  * have constraints on va-space that make this illegal (IA64) -
 557                  * for the others its just a little faster.
 558                  */
 559                 free_pgd_range(tlb, old_start, old_end, new_end,
 560                         vma->vm_next ? vma->vm_next->vm_start : 0);
 561         }
 562         tlb_finish_mmu(tlb, new_end, old_end);
 563
 564         /*
 565          * shrink the vma to just the new range.
 566          */
 567         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 568
 569         return 0;
 570 }
 571
 572 #define EXTRA_STACK_VM_PAGES    20      /* random */
 573
 574 /*
 575  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 576  * the stack is optionally relocated, and some extra space is added.
 577  */
 578 int setup_arg_pages(struct linux_binprm *bprm,
 579                     unsigned long stack_top,
 580                     int executable_stack)
 581 {
 582         unsigned long ret;
 583         unsigned long stack_shift;
 584         struct mm_struct *mm = current->mm;
 585         struct vm_area_struct *vma = bprm->vma;
 586         struct vm_area_struct *prev = NULL;
 587         unsigned long vm_flags;
 588         unsigned long stack_base;
 589
 590 #ifdef CONFIG_STACK_GROWSUP
 591         /* Limit stack size to 1GB */
 592         stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max;
 593         if (stack_base > (1 << 30))
 594                 stack_base = 1 << 30;
 595
 596         /* Make sure we didn't let the argument array grow too large. */
 597         if (vma->vm_end - vma->vm_start > stack_base)
 598                 return -ENOMEM;
 599
 600         stack_base = PAGE_ALIGN(stack_top - stack_base);
 601
 602         stack_shift = vma->vm_start - stack_base;
 603         mm->arg_start = bprm->p - stack_shift;
 604         bprm->p = vma->vm_end - stack_shift;
 605 #else
 606         stack_top = arch_align_stack(stack_top);
 607         stack_top = PAGE_ALIGN(stack_top);
 608         stack_shift = vma->vm_end - stack_top;
 609
 610         bprm->p -= stack_shift;
 611         mm->arg_start = bprm->p;
 612 #endif
 613
 614         if (bprm->loader)
 615                 bprm->loader -= stack_shift;
 616         bprm->exec -= stack_shift;
 617
 618         down_write(&mm->mmap_sem);
 619         vm_flags = VM_STACK_FLAGS;
 620
 621         /*
 622          * Adjust stack execute permissions; explicitly enable for
 623          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 624          * (arch default) otherwise.
 625          */
 626         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 627                 vm_flags |= VM_EXEC;
 628         else if (executable_stack == EXSTACK_DISABLE_X)
 629                 vm_flags &= ~VM_EXEC;
 630         vm_flags |= mm->def_flags;
 631
 632         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 633                         vm_flags);
 634         if (ret)
 635                 goto out_unlock;
 636         BUG_ON(prev != vma);
 637
 638         /* Move stack pages down in memory. */
 639         if (stack_shift) {
 640                 ret = shift_arg_pages(vma, stack_shift);
 641                 if (ret) {
 642                         up_write(&mm->mmap_sem);
 643                         return ret;
 644                 }
 645         }
 646
 647 #ifdef CONFIG_STACK_GROWSUP
 648         stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE;
 649 #else
 650         stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE;
 651 #endif
 652         ret = expand_stack(vma, stack_base);
 653         if (ret)
 654                 ret = -EFAULT;
 655
 656 out_unlock:
 657         up_write(&mm->mmap_sem);
 658         return 0;
 659 }
 660 EXPORT_SYMBOL(setup_arg_pages);
 661
 662 #endif /* CONFIG_MMU */
 663
 664 struct file *open_exec(const char *name)
 665 {
 666         struct nameidata nd;
 667         struct file *file;
 668         int err;
 669
 670         err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd,
 671                                 FMODE_READ|FMODE_EXEC);
 672         if (err)
 673                 goto out;
 674
 675         err = -EACCES;
 676         if (!S_ISREG(nd.path.dentry->d_inode->i_mode))
 677                 goto out_path_put;
 678
 679         if (nd.path.mnt->mnt_flags & MNT_NOEXEC)
 680                 goto out_path_put;
 681
 682         err = inode_permission(nd.path.dentry->d_inode, MAY_EXEC | MAY_OPEN);
 683         if (err)
 684                 goto out_path_put;
 685
 686         file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE);
 687         if (IS_ERR(file))
 688                 return file;
 689
 690         fsnotify_open(file->f_path.dentry);
 691
 692         err = deny_write_access(file);
 693         if (err) {
 694                 fput(file);
 695                 goto out;
 696         }
 697
 698         return file;
 699
 700  out_path_put:
 701         release_open_intent(&nd);
 702         path_put(&nd.path);
 703  out:
 704         return ERR_PTR(err);
 705 }
 706 EXPORT_SYMBOL(open_exec);
 707
 708 int kernel_read(struct file *file, unsigned long offset,
 709         char *addr, unsigned long count)
 710 {
 711         mm_segment_t old_fs;
 712         loff_t pos = offset;
 713         int result;
 714
 715         old_fs = get_fs();
 716         set_fs(get_ds());
 717         /* The cast to a user pointer is valid due to the set_fs() */
 718         result = vfs_read(file, (void __user *)addr, count, &pos);
 719         set_fs(old_fs);
 720         return result;
 721 }
 722
 723 EXPORT_SYMBOL(kernel_read);
 724
 725 static int exec_mmap(struct mm_struct *mm)
 726 {
 727         struct task_struct *tsk;
 728         struct mm_struct * old_mm, *active_mm;
 729
 730         /* Notify parent that we're no longer interested in the old VM */
 731         tsk = current;
 732         old_mm = current->mm;
 733         mm_release(tsk, old_mm);
 734
 735         if (old_mm) {
 736                 /*
 737                  * Make sure that if there is a core dump in progress
 738                  * for the old mm, we get out and die instead of going
 739                  * through with the exec.  We must hold mmap_sem around
 740                  * checking core_state and changing tsk->mm.
 741                  */
 742                 down_read(&old_mm->mmap_sem);
 743                 if (unlikely(old_mm->core_state)) {
 744                         up_read(&old_mm->mmap_sem);
 745                         return -EINTR;
 746                 }
 747         }
 748         task_lock(tsk);
 749         active_mm = tsk->active_mm;
 750         tsk->mm = mm;
 751         tsk->active_mm = mm;
 752         activate_mm(active_mm, mm);
 753         task_unlock(tsk);
 754         arch_pick_mmap_layout(mm);
 755         if (old_mm) {
 756                 up_read(&old_mm->mmap_sem);
 757                 BUG_ON(active_mm != old_mm);
 758                 mm_update_next_owner(old_mm);
 759                 mmput(old_mm);
 760                 return 0;
 761         }
 762         mmdrop(active_mm);
 763         return 0;
 764 }
 765
 766 /*
 767  * This function makes sure the current process has its own signal table,
 768  * so that flush_signal_handlers can later reset the handlers without
 769  * disturbing other processes.  (Other processes might share the signal
 770  * table via the CLONE_SIGHAND option to clone().)
 771  */
 772 static int de_thread(struct task_struct *tsk)
 773 {
 774         struct signal_struct *sig = tsk->signal;
 775         struct sighand_struct *oldsighand = tsk->sighand;
 776         spinlock_t *lock = &oldsighand->siglock;
 777         int count;
 778
 779         if (thread_group_empty(tsk))
 780                 goto no_thread_group;
 781
 782         /*
 783          * Kill all other threads in the thread group.
 784          */
 785         spin_lock_irq(lock);
 786         if (signal_group_exit(sig)) {
 787                 /*
 788                  * Another group action in progress, just
 789                  * return so that the signal is processed.
 790                  */
 791                 spin_unlock_irq(lock);
 792                 return -EAGAIN;
 793         }
 794         sig->group_exit_task = tsk;
 795         zap_other_threads(tsk);
 796
 797         /* Account for the thread group leader hanging around: */
 798         count = thread_group_leader(tsk) ? 1 : 2;
 799         sig->notify_count = count;
 800         while (atomic_read(&sig->count) > count) {
 801                 __set_current_state(TASK_UNINTERRUPTIBLE);
 802                 spin_unlock_irq(lock);
 803                 schedule();
 804                 spin_lock_irq(lock);
 805         }
 806         spin_unlock_irq(lock);
 807
 808         /*
 809          * At this point all other threads have exited, all we have to
 810          * do is to wait for the thread group leader to become inactive,
 811          * and to assume its PID:
 812          */
 813         if (!thread_group_leader(tsk)) {
 814                 struct task_struct *leader = tsk->group_leader;
 815
 816                 sig->notify_count = -1; /* for exit_notify() */
 817                 for (;;) {
 818                         write_lock_irq(&tasklist_lock);
 819                         if (likely(leader->exit_state))
 820                                 break;
 821                         __set_current_state(TASK_UNINTERRUPTIBLE);
 822                         write_unlock_irq(&tasklist_lock);
 823                         schedule();
 824                 }
 825
 826                 /*
 827                  * The only record we have of the real-time age of a
 828                  * process, regardless of execs it's done, is start_time.
 829                  * All the past CPU time is accumulated in signal_struct
 830                  * from sister threads now dead.  But in this non-leader
 831                  * exec, nothing survives from the original leader thread,
 832                  * whose birth marks the true age of this process now.
 833                  * When we take on its identity by switching to its PID, we
 834                  * also take its birthdate (always earlier than our own).
 835                  */
 836                 tsk->start_time = leader->start_time;
 837
 838                 BUG_ON(!same_thread_group(leader, tsk));
 839                 BUG_ON(has_group_leader_pid(tsk));
 840                 /*
 841                  * An exec() starts a new thread group with the
 842                  * TGID of the previous thread group. Rehash the
 843                  * two threads with a switched PID, and release
 844                  * the former thread group leader:
 845                  */
 846
 847                 /* Become a process group leader with the old leader's pid.
 848                  * The old leader becomes a thread of the this thread group.
 849                  * Note: The old leader also uses this pid until release_task
 850                  *       is called.  Odd but simple and correct.
 851                  */
 852                 detach_pid(tsk, PIDTYPE_PID);
 853                 tsk->pid = leader->pid;
 854                 attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
 855                 transfer_pid(leader, tsk, PIDTYPE_PGID);
 856                 transfer_pid(leader, tsk, PIDTYPE_SID);
 857                 list_replace_rcu(&leader->tasks, &tsk->tasks);
 858
 859                 tsk->group_leader = tsk;
 860                 leader->group_leader = tsk;
 861
 862                 tsk->exit_signal = SIGCHLD;
 863
 864                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 865                 leader->exit_state = EXIT_DEAD;
 866                 write_unlock_irq(&tasklist_lock);
 867
 868                 release_task(leader);
 869         }
 870
 871         sig->group_exit_task = NULL;
 872         sig->notify_count = 0;
 873
 874 no_thread_group:
 875         exit_itimers(sig);
 876         flush_itimer_signals();
 877
 878         if (atomic_read(&oldsighand->count) != 1) {
 879                 struct sighand_struct *newsighand;
 880                 /*
 881                  * This ->sighand is shared with the CLONE_SIGHAND
 882                  * but not CLONE_THREAD task, switch to the new one.
 883                  */
 884                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 885                 if (!newsighand)
 886                         return -ENOMEM;
 887
 888                 atomic_set(&newsighand->count, 1);
 889                 memcpy(newsighand->action, oldsighand->action,
 890                        sizeof(newsighand->action));
 891
 892                 write_lock_irq(&tasklist_lock);
 893                 spin_lock(&oldsighand->siglock);
 894                 rcu_assign_pointer(tsk->sighand, newsighand);
 895                 spin_unlock(&oldsighand->siglock);
 896                 write_unlock_irq(&tasklist_lock);
 897
 898                 __cleanup_sighand(oldsighand);
 899         }
 900
 901         BUG_ON(!thread_group_leader(tsk));
 902         return 0;
 903 }
 904
 905 /*
 906  * These functions flushes out all traces of the currently running executable
 907  * so that a new one can be started
 908  */
 909 static void flush_old_files(struct files_struct * files)
 910 {
 911         long j = -1;
 912         struct fdtable *fdt;
 913
 914         spin_lock(&files->file_lock);
 915         for (;;) {
 916                 unsigned long set, i;
 917
 918                 j++;
 919                 i = j * __NFDBITS;
 920                 fdt = files_fdtable(files);
 921                 if (i >= fdt->max_fds)
 922                         break;
 923                 set = fdt->close_on_exec->fds_bits[j];
 924                 if (!set)
 925                         continue;
 926                 fdt->close_on_exec->fds_bits[j] = 0;
 927                 spin_unlock(&files->file_lock);
 928                 for ( ; set ; i++,set >>= 1) {
 929                         if (set & 1) {
 930                                 sys_close(i);
 931                         }
 932                 }
 933                 spin_lock(&files->file_lock);
 934
 935         }
 936         spin_unlock(&files->file_lock);
 937 }
 938
 939 char *get_task_comm(char *buf, struct task_struct *tsk)
 940 {
 941         /* buf must be at least sizeof(tsk->comm) in size */
 942         task_lock(tsk);
 943         strncpy(buf, tsk->comm, sizeof(tsk->comm));
 944         task_unlock(tsk);
 945         return buf;
 946 }
 947
 948 void set_task_comm(struct task_struct *tsk, char *buf)
 949 {
 950         task_lock(tsk);
 951         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
 952         task_unlock(tsk);
 953 }
 954
 955 int flush_old_exec(struct linux_binprm * bprm)
 956 {
 957         char * name;
 958         int i, ch, retval;
 959         char tcomm[sizeof(current->comm)];
 960
 961         /*
 962          * Make sure we have a private signal table and that
 963          * we are unassociated from the previous thread group.
 964          */
 965         retval = de_thread(current);
 966         if (retval)
 967                 goto out;
 968
 969         set_mm_exe_file(bprm->mm, bprm->file);
 970
 971         /*
 972          * Release all of the old mmap stuff
 973          */
 974         retval = exec_mmap(bprm->mm);
 975         if (retval)
 976                 goto out;
 977
 978         bprm->mm = NULL;                /* We're using it now */
 979
 980         /* This is the point of no return */
 981         current->sas_ss_sp = current->sas_ss_size = 0;
 982
 983         if (current_euid() == current_uid() && current_egid() == current_gid())
 984                 set_dumpable(current->mm, 1);
 985         else
 986                 set_dumpable(current->mm, suid_dumpable);
 987
 988         name = bprm->filename;
 989
 990         /* Copies the binary name from after last slash */
 991         for (i=0; (ch = *(name++)) != '\0';) {
 992                 if (ch == '/')
 993                         i = 0; /* overwrite what we wrote */
 994                 else
 995                         if (i < (sizeof(tcomm) - 1))
 996                                 tcomm[i++] = ch;
 997         }
 998         tcomm[i] = '\0';
 999         set_task_comm(current, tcomm);
1000
1001         current->flags &= ~PF_RANDOMIZE;
1002         flush_thread();
1003
1004         /* Set the new mm task size. We have to do that late because it may
1005          * depend on TIF_32BIT which is only updated in flush_thread() on
1006          * some architectures like powerpc
1007          */
1008         current->mm->task_size = TASK_SIZE;
1009
1010         /* install the new credentials */
1011         if (bprm->cred->uid != current_euid() ||
1012             bprm->cred->gid != current_egid()) {
1013                 current->pdeath_signal = 0;
1014         } else if (file_permission(bprm->file, MAY_READ) ||
1015                    bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) {
1016                 set_dumpable(current->mm, suid_dumpable);
1017         }
1018
1019         current->personality &= ~bprm->per_clear;
1020
1021         /* An exec changes our domain. We are no longer part of the thread
1022            group */
1023
1024         current->self_exec_id++;
1025
1026         flush_signal_handlers(current, 0);
1027         flush_old_files(current->files);
1028
1029         return 0;
1030
1031 out:
1032         return retval;
1033 }
1034
1035 EXPORT_SYMBOL(flush_old_exec);
1036
1037 /*
1038  * install the new credentials for this executable
1039  */
1040 void install_exec_creds(struct linux_binprm *bprm)
1041 {
1042         security_bprm_committing_creds(bprm);
1043
1044         commit_creds(bprm->cred);
1045         bprm->cred = NULL;
1046
1047         /* cred_exec_mutex must be held at least to this point to prevent
1048          * ptrace_attach() from altering our determination of the task's
1049          * credentials; any time after this it may be unlocked */
1050
1051         security_bprm_committed_creds(bprm);
1052 }
1053 EXPORT_SYMBOL(install_exec_creds);
1054
1055 /*
1056  * determine how safe it is to execute the proposed program
1057  * - the caller must hold current->cred_exec_mutex to protect against
1058  *   PTRACE_ATTACH
1059  */
1060 void check_unsafe_exec(struct linux_binprm *bprm)
1061 {
1062         struct task_struct *p = current;
1063
1064         bprm->unsafe = tracehook_unsafe_exec(p);
1065
1066         if (atomic_read(&p->fs->count) > 1 ||
1067             atomic_read(&p->files->count) > 1 ||
1068             atomic_read(&p->sighand->count) > 1)
1069                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1070 }
1071
1072 /*
1073  * Fill the binprm structure from the inode.
1074  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1075  *
1076  * This may be called multiple times for binary chains (scripts for example).
1077  */
1078 int prepare_binprm(struct linux_binprm *bprm)
1079 {
1080         umode_t mode;
1081         struct inode * inode = bprm->file->f_path.dentry->d_inode;
1082         int retval;
1083
1084         mode = inode->i_mode;
1085         if (bprm->file->f_op == NULL)
1086                 return -EACCES;
1087
1088         /* clear any previous set[ug]id data from a previous binary */
1089         bprm->cred->euid = current_euid();
1090         bprm->cred->egid = current_egid();
1091
1092         if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1093                 /* Set-uid? */
1094                 if (mode & S_ISUID) {
1095                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1096                         bprm->cred->euid = inode->i_uid;
1097                 }
1098
1099                 /* Set-gid? */
1100                 /*
1101                  * If setgid is set but no group execute bit then this
1102                  * is a candidate for mandatory locking, not a setgid
1103                  * executable.
1104                  */
1105                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1106                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1107                         bprm->cred->egid = inode->i_gid;
1108                 }
1109         }
1110
1111         /* fill in binprm security blob */
1112         retval = security_bprm_set_creds(bprm);
1113         if (retval)
1114                 return retval;
1115         bprm->cred_prepared = 1;
1116
1117         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1118         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1119 }
1120
1121 EXPORT_SYMBOL(prepare_binprm);
1122
1123 /*
1124  * Arguments are '\0' separated strings found at the location bprm->p
1125  * points to; chop off the first by relocating brpm->p to right after
1126  * the first '\0' encountered.
1127  */
1128 int remove_arg_zero(struct linux_binprm *bprm)
1129 {
1130         int ret = 0;
1131         unsigned long offset;
1132         char *kaddr;
1133         struct page *page;
1134
1135         if (!bprm->argc)
1136                 return 0;
1137
1138         do {
1139                 offset = bprm->p & ~PAGE_MASK;
1140                 page = get_arg_page(bprm, bprm->p, 0);
1141                 if (!page) {
1142                         ret = -EFAULT;
1143                         goto out;
1144                 }
1145                 kaddr = kmap_atomic(page, KM_USER0);
1146
1147                 for (; offset < PAGE_SIZE && kaddr[offset];
1148                                 offset++, bprm->p++)
1149                         ;
1150
1151                 kunmap_atomic(kaddr, KM_USER0);
1152                 put_arg_page(page);
1153
1154                 if (offset == PAGE_SIZE)
1155                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1156         } while (offset == PAGE_SIZE);
1157
1158         bprm->p++;
1159         bprm->argc--;
1160         ret = 0;
1161
1162 out:
1163         return ret;
1164 }
1165 EXPORT_SYMBOL(remove_arg_zero);
1166
1167 /*
1168  * cycle the list of binary formats handler, until one recognizes the image
1169  */
1170 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1171 {
1172         unsigned int depth = bprm->recursion_depth;
1173         int try,retval;
1174         struct linux_binfmt *fmt;
1175
1176         retval = security_bprm_check(bprm);
1177         if (retval)
1178                 return retval;
1179
1180         /* kernel module loader fixup */
1181         /* so we don't try to load run modprobe in kernel space. */
1182         set_fs(USER_DS);
1183
1184         retval = audit_bprm(bprm);
1185         if (retval)
1186                 return retval;
1187
1188         retval = -ENOENT;
1189         for (try=0; try<2; try++) {
1190                 read_lock(&binfmt_lock);
1191                 list_for_each_entry(fmt, &formats, lh) {
1192                         int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1193                         if (!fn)
1194                                 continue;
1195                         if (!try_module_get(fmt->module))
1196                                 continue;
1197                         read_unlock(&binfmt_lock);
1198                         retval = fn(bprm, regs);
1199                         /*
1200                          * Restore the depth counter to its starting value
1201                          * in this call, so we don't have to rely on every
1202                          * load_binary function to restore it on return.
1203                          */
1204                         bprm->recursion_depth = depth;
1205                         if (retval >= 0) {
1206                                 if (depth == 0)
1207                                         tracehook_report_exec(fmt, bprm, regs);
1208                                 put_binfmt(fmt);
1209                                 allow_write_access(bprm->file);
1210                                 if (bprm->file)
1211                                         fput(bprm->file);
1212                                 bprm->file = NULL;
1213                                 current->did_exec = 1;
1214                                 proc_exec_connector(current);
1215                                 return retval;
1216                         }
1217                         read_lock(&binfmt_lock);
1218                         put_binfmt(fmt);
1219                         if (retval != -ENOEXEC || bprm->mm == NULL)
1220                                 break;
1221                         if (!bprm->file) {
1222                                 read_unlock(&binfmt_lock);
1223                                 return retval;
1224                         }
1225                 }
1226                 read_unlock(&binfmt_lock);
1227                 if (retval != -ENOEXEC || bprm->mm == NULL) {
1228                         break;
1229 #ifdef CONFIG_MODULES
1230                 } else {
1231 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1232                         if (printable(bprm->buf[0]) &&
1233                             printable(bprm->buf[1]) &&
1234                             printable(bprm->buf[2]) &&
1235                             printable(bprm->buf[3]))
1236                                 break; /* -ENOEXEC */
1237                         request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1238 #endif
1239                 }
1240         }
1241         return retval;
1242 }
1243
1244 EXPORT_SYMBOL(search_binary_handler);
1245
1246 void free_bprm(struct linux_binprm *bprm)
1247 {
1248         free_arg_pages(bprm);
1249         if (bprm->cred)
1250                 abort_creds(bprm->cred);
1251         kfree(bprm);
1252 }
1253
1254 /*
1255  * sys_execve() executes a new program.
1256  */
1257 int do_execve(char * filename,
1258         char __user *__user *argv,
1259         char __user *__user *envp,
1260         struct pt_regs * regs)
1261 {
1262         struct linux_binprm *bprm;
1263         struct file *file;
1264         struct files_struct *displaced;
1265         int retval;
1266
1267         retval = unshare_files(&displaced);
1268         if (retval)
1269                 goto out_ret;
1270
1271         retval = -ENOMEM;
1272         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1273         if (!bprm)
1274                 goto out_files;
1275
1276         retval = mutex_lock_interruptible(&current->cred_exec_mutex);
1277         if (retval < 0)
1278                 goto out_free;
1279
1280         retval = -ENOMEM;
1281         bprm->cred = prepare_exec_creds();
1282         if (!bprm->cred)
1283                 goto out_unlock;
1284         check_unsafe_exec(bprm);
1285
1286         file = open_exec(filename);
1287         retval = PTR_ERR(file);
1288         if (IS_ERR(file))
1289                 goto out_unlock;
1290
1291         sched_exec();
1292
1293         bprm->file = file;
1294         bprm->filename = filename;
1295         bprm->interp = filename;
1296
1297         retval = bprm_mm_init(bprm);
1298         if (retval)
1299                 goto out_file;
1300
1301         bprm->argc = count(argv, MAX_ARG_STRINGS);
1302         if ((retval = bprm->argc) < 0)
1303                 goto out;
1304
1305         bprm->envc = count(envp, MAX_ARG_STRINGS);
1306         if ((retval = bprm->envc) < 0)
1307                 goto out;
1308
1309         retval = prepare_binprm(bprm);
1310         if (retval < 0)
1311                 goto out;
1312
1313         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1314         if (retval < 0)
1315                 goto out;
1316
1317         bprm->exec = bprm->p;
1318         retval = copy_strings(bprm->envc, envp, bprm);
1319         if (retval < 0)
1320                 goto out;
1321
1322         retval = copy_strings(bprm->argc, argv, bprm);
1323         if (retval < 0)
1324                 goto out;
1325
1326         current->flags &= ~PF_KTHREAD;
1327         retval = search_binary_handler(bprm,regs);
1328         if (retval < 0)
1329                 goto out;
1330
1331         /* execve succeeded */
1332         mutex_unlock(&current->cred_exec_mutex);
1333         acct_update_integrals(current);
1334         free_bprm(bprm);
1335         if (displaced)
1336                 put_files_struct(displaced);
1337         return retval;
1338
1339 out:
1340         if (bprm->mm)
1341                 mmput (bprm->mm);
1342
1343 out_file:
1344         if (bprm->file) {
1345                 allow_write_access(bprm->file);
1346                 fput(bprm->file);
1347         }
1348
1349 out_unlock:
1350         mutex_unlock(&current->cred_exec_mutex);
1351
1352 out_free:
1353         free_bprm(bprm);
1354
1355 out_files:
1356         if (displaced)
1357                 reset_files_struct(displaced);
1358 out_ret:
1359         return retval;
1360 }
1361
1362 int set_binfmt(struct linux_binfmt *new)
1363 {
1364         struct linux_binfmt *old = current->binfmt;
1365
1366         if (new) {
1367                 if (!try_module_get(new->module))
1368                         return -1;
1369         }
1370         current->binfmt = new;
1371         if (old)
1372                 module_put(old->module);
1373         return 0;
1374 }
1375
1376 EXPORT_SYMBOL(set_binfmt);
1377
1378 /* format_corename will inspect the pattern parameter, and output a
1379  * name into corename, which must have space for at least
1380  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1381  */
1382 static int format_corename(char *corename, long signr)
1383 {
1384         const struct cred *cred = current_cred();
1385         const char *pat_ptr = core_pattern;
1386         int ispipe = (*pat_ptr == '|');
1387         char *out_ptr = corename;
1388         char *const out_end = corename + CORENAME_MAX_SIZE;
1389         int rc;
1390         int pid_in_pattern = 0;
1391
1392         /* Repeat as long as we have more pattern to process and more output
1393            space */
1394         while (*pat_ptr) {
1395                 if (*pat_ptr != '%') {
1396                         if (out_ptr == out_end)
1397                                 goto out;
1398                         *out_ptr++ = *pat_ptr++;
1399                 } else {
1400                         switch (*++pat_ptr) {
1401                         case 0:
1402                                 goto out;
1403                         /* Double percent, output one percent */
1404                         case '%':
1405                                 if (out_ptr == out_end)
1406                                         goto out;
1407                                 *out_ptr++ = '%';
1408                                 break;
1409                         /* pid */
1410                         case 'p':
1411                                 pid_in_pattern = 1;
1412                                 rc = snprintf(out_ptr, out_end - out_ptr,
1413                                               "%d", task_tgid_vnr(current));
1414                                 if (rc > out_end - out_ptr)
1415                                         goto out;
1416                                 out_ptr += rc;
1417                                 break;
1418                         /* uid */
1419                         case 'u':
1420                                 rc = snprintf(out_ptr, out_end - out_ptr,
1421                                               "%d", cred->uid);
1422                                 if (rc > out_end - out_ptr)
1423                                         goto out;
1424                                 out_ptr += rc;
1425                                 break;
1426                         /* gid */
1427                         case 'g':
1428                                 rc = snprintf(out_ptr, out_end - out_ptr,
1429                                               "%d", cred->gid);
1430                                 if (rc > out_end - out_ptr)
1431                                         goto out;
1432                                 out_ptr += rc;
1433                                 break;
1434                         /* signal that caused the coredump */
1435                         case 's':
1436                                 rc = snprintf(out_ptr, out_end - out_ptr,
1437                                               "%ld", signr);
1438                                 if (rc > out_end - out_ptr)
1439                                         goto out;
1440                                 out_ptr += rc;
1441                                 break;
1442                         /* UNIX time of coredump */
1443                         case 't': {
1444                                 struct timeval tv;
1445                                 do_gettimeofday(&tv);
1446                                 rc = snprintf(out_ptr, out_end - out_ptr,
1447                                               "%lu", tv.tv_sec);
1448                                 if (rc > out_end - out_ptr)
1449                                         goto out;
1450                                 out_ptr += rc;
1451                                 break;
1452                         }
1453                         /* hostname */
1454                         case 'h':
1455                                 down_read(&uts_sem);
1456                                 rc = snprintf(out_ptr, out_end - out_ptr,
1457                                               "%s", utsname()->nodename);
1458                                 up_read(&uts_sem);
1459                                 if (rc > out_end - out_ptr)
1460                                         goto out;
1461                                 out_ptr += rc;
1462                                 break;
1463                         /* executable */
1464                         case 'e':
1465                                 rc = snprintf(out_ptr, out_end - out_ptr,
1466                                               "%s", current->comm);
1467                                 if (rc > out_end - out_ptr)
1468                                         goto out;
1469                                 out_ptr += rc;
1470                                 break;
1471                         /* core limit size */
1472                         case 'c':
1473                                 rc = snprintf(out_ptr, out_end - out_ptr,
1474                                               "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur);
1475                                 if (rc > out_end - out_ptr)
1476                                         goto out;
1477                                 out_ptr += rc;
1478                                 break;
1479                         default:
1480                                 break;
1481                         }
1482                         ++pat_ptr;
1483                 }
1484         }
1485         /* Backward compatibility with core_uses_pid:
1486          *
1487          * If core_pattern does not include a %p (as is the default)
1488          * and core_uses_pid is set, then .%pid will be appended to
1489          * the filename. Do not do this for piped commands. */
1490         if (!ispipe && !pid_in_pattern && core_uses_pid) {
1491                 rc = snprintf(out_ptr, out_end - out_ptr,
1492                               ".%d", task_tgid_vnr(current));
1493                 if (rc > out_end - out_ptr)
1494                         goto out;
1495                 out_ptr += rc;
1496         }
1497 out:
1498         *out_ptr = 0;
1499         return ispipe;
1500 }
1501
1502 static int zap_process(struct task_struct *start)
1503 {
1504         struct task_struct *t;
1505         int nr = 0;
1506
1507         start->signal->flags = SIGNAL_GROUP_EXIT;
1508         start->signal->group_stop_count = 0;
1509
1510         t = start;
1511         do {
1512                 if (t != current && t->mm) {
1513                         sigaddset(&t->pending.signal, SIGKILL);
1514                         signal_wake_up(t, 1);
1515                         nr++;
1516                 }
1517         } while_each_thread(start, t);
1518
1519         return nr;
1520 }
1521
1522 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1523                                 struct core_state *core_state, int exit_code)
1524 {
1525         struct task_struct *g, *p;
1526         unsigned long flags;
1527         int nr = -EAGAIN;
1528
1529         spin_lock_irq(&tsk->sighand->siglock);
1530         if (!signal_group_exit(tsk->signal)) {
1531                 mm->core_state = core_state;
1532                 tsk->signal->group_exit_code = exit_code;
1533                 nr = zap_process(tsk);
1534         }
1535         spin_unlock_irq(&tsk->sighand->siglock);
1536         if (unlikely(nr < 0))
1537                 return nr;
1538
1539         if (atomic_read(&mm->mm_users) == nr + 1)
1540                 goto done;
1541         /*
1542          * We should find and kill all tasks which use this mm, and we should
1543          * count them correctly into ->nr_threads. We don't take tasklist
1544          * lock, but this is safe wrt:
1545          *
1546          * fork:
1547          *      None of sub-threads can fork after zap_process(leader). All
1548          *      processes which were created before this point should be
1549          *      visible to zap_threads() because copy_process() adds the new
1550          *      process to the tail of init_task.tasks list, and lock/unlock
1551          *      of ->siglock provides a memory barrier.
1552          *
1553          * do_exit:
1554          *      The caller holds mm->mmap_sem. This means that the task which
1555          *      uses this mm can't pass exit_mm(), so it can't exit or clear
1556          *      its ->mm.
1557          *
1558          * de_thread:
1559          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
1560          *      we must see either old or new leader, this does not matter.
1561          *      However, it can change p->sighand, so lock_task_sighand(p)
1562          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
1563          *      it can't fail.
1564          *
1565          *      Note also that "g" can be the old leader with ->mm == NULL
1566          *      and already unhashed and thus removed from ->thread_group.
1567          *      This is OK, __unhash_process()->list_del_rcu() does not
1568          *      clear the ->next pointer, we will find the new leader via
1569          *      next_thread().
1570          */
1571         rcu_read_lock();
1572         for_each_process(g) {
1573                 if (g == tsk->group_leader)
1574                         continue;
1575                 if (g->flags & PF_KTHREAD)
1576                         continue;
1577                 p = g;
1578                 do {
1579                         if (p->mm) {
1580                                 if (unlikely(p->mm == mm)) {
1581                                         lock_task_sighand(p, &flags);
1582                                         nr += zap_process(p);
1583                                         unlock_task_sighand(p, &flags);
1584                                 }
1585                                 break;
1586                         }
1587                 } while_each_thread(g, p);
1588         }
1589         rcu_read_unlock();
1590 done:
1591         atomic_set(&core_state->nr_threads, nr);
1592         return nr;
1593 }
1594
1595 static int coredump_wait(int exit_code, struct core_state *core_state)
1596 {
1597         struct task_struct *tsk = current;
1598         struct mm_struct *mm = tsk->mm;
1599         struct completion *vfork_done;
1600         int core_waiters;
1601
1602         init_completion(&core_state->startup);
1603         core_state->dumper.task = tsk;
1604         core_state->dumper.next = NULL;
1605         core_waiters = zap_threads(tsk, mm, core_state, exit_code);
1606         up_write(&mm->mmap_sem);
1607
1608         if (unlikely(core_waiters < 0))
1609                 goto fail;
1610
1611         /*
1612          * Make sure nobody is waiting for us to release the VM,
1613          * otherwise we can deadlock when we wait on each other
1614          */
1615         vfork_done = tsk->vfork_done;
1616         if (vfork_done) {
1617                 tsk->vfork_done = NULL;
1618                 complete(vfork_done);
1619         }
1620
1621         if (core_waiters)
1622                 wait_for_completion(&core_state->startup);
1623 fail:
1624         return core_waiters;
1625 }
1626
1627 static void coredump_finish(struct mm_struct *mm)
1628 {
1629         struct core_thread *curr, *next;
1630         struct task_struct *task;
1631
1632         next = mm->core_state->dumper.next;
1633         while ((curr = next) != NULL) {
1634                 next = curr->next;
1635                 task = curr->task;
1636                 /*
1637                  * see exit_mm(), curr->task must not see
1638                  * ->task == NULL before we read ->next.
1639                  */
1640                 smp_mb();
1641                 curr->task = NULL;
1642                 wake_up_process(task);
1643         }
1644
1645         mm->core_state = NULL;
1646 }
1647
1648 /*
1649  * set_dumpable converts traditional three-value dumpable to two flags and
1650  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1651  * these bits are not changed atomically.  So get_dumpable can observe the
1652  * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1653  * return either old dumpable or new one by paying attention to the order of
1654  * modifying the bits.
1655  *
1656  * dumpable |   mm->flags (binary)
1657  * old  new | initial interim  final
1658  * ---------+-----------------------
1659  *  0    1  |   00      01      01
1660  *  0    2  |   00      10(*)   11
1661  *  1    0  |   01      00      00
1662  *  1    2  |   01      11      11
1663  *  2    0  |   11      10(*)   00
1664  *  2    1  |   11      11      01
1665  *
1666  * (*) get_dumpable regards interim value of 10 as 11.
1667  */
1668 void set_dumpable(struct mm_struct *mm, int value)
1669 {
1670         switch (value) {
1671         case 0:
1672                 clear_bit(MMF_DUMPABLE, &mm->flags);
1673                 smp_wmb();
1674                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1675                 break;
1676         case 1:
1677                 set_bit(MMF_DUMPABLE, &mm->flags);
1678                 smp_wmb();
1679                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1680                 break;
1681         case 2:
1682                 set_bit(MMF_DUMP_SECURELY, &mm->flags);
1683                 smp_wmb();
1684                 set_bit(MMF_DUMPABLE, &mm->flags);
1685                 break;
1686         }
1687 }
1688
1689 int get_dumpable(struct mm_struct *mm)
1690 {
1691         int ret;
1692
1693         ret = mm->flags & 0x3;
1694         return (ret >= 2) ? 2 : ret;
1695 }
1696
1697 int do_coredump(long signr, int exit_code, struct pt_regs * regs)
1698 {
1699         struct core_state core_state;
1700         char corename[CORENAME_MAX_SIZE + 1];
1701         struct mm_struct *mm = current->mm;
1702         struct linux_binfmt * binfmt;
1703         struct inode * inode;
1704         struct file * file;
1705         const struct cred *old_cred;
1706         struct cred *cred;
1707         int retval = 0;
1708         int flag = 0;
1709         int ispipe = 0;
1710         unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
1711         char **helper_argv = NULL;
1712         int helper_argc = 0;
1713         char *delimit;
1714
1715         audit_core_dumps(signr);
1716
1717         binfmt = current->binfmt;
1718         if (!binfmt || !binfmt->core_dump)
1719                 goto fail;
1720
1721         cred = prepare_creds();
1722         if (!cred) {
1723                 retval = -ENOMEM;
1724                 goto fail;
1725         }
1726
1727         down_write(&mm->mmap_sem);
1728         /*
1729          * If another thread got here first, or we are not dumpable, bail out.
1730          */
1731         if (mm->core_state || !get_dumpable(mm)) {
1732                 up_write(&mm->mmap_sem);
1733                 put_cred(cred);
1734                 goto fail;
1735         }
1736
1737         /*
1738          *      We cannot trust fsuid as being the "true" uid of the
1739          *      process nor do we know its entire history. We only know it
1740          *      was tainted so we dump it as root in mode 2.
1741          */
1742         if (get_dumpable(mm) == 2) {    /* Setuid core dump mode */
1743                 flag = O_EXCL;          /* Stop rewrite attacks */
1744                 cred->fsuid = 0;        /* Dump root private */
1745         }
1746
1747         retval = coredump_wait(exit_code, &core_state);
1748         if (retval < 0) {
1749                 put_cred(cred);
1750                 goto fail;
1751         }
1752
1753         old_cred = override_creds(cred);
1754
1755         /*
1756          * Clear any false indication of pending signals that might
1757          * be seen by the filesystem code called to write the core file.
1758          */
1759         clear_thread_flag(TIF_SIGPENDING);
1760
1761         /*
1762          * lock_kernel() because format_corename() is controlled by sysctl, which
1763          * uses lock_kernel()
1764          */
1765         lock_kernel();
1766         ispipe = format_corename(corename, signr);
1767         unlock_kernel();
1768         /*
1769          * Don't bother to check the RLIMIT_CORE value if core_pattern points
1770          * to a pipe.  Since we're not writing directly to the filesystem
1771          * RLIMIT_CORE doesn't really apply, as no actual core file will be
1772          * created unless the pipe reader choses to write out the core file
1773          * at which point file size limits and permissions will be imposed
1774          * as it does with any other process
1775          */
1776         if ((!ispipe) && (core_limit < binfmt->min_coredump))
1777                 goto fail_unlock;
1778
1779         if (ispipe) {
1780                 helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc);
1781                 /* Terminate the string before the first option */
1782                 delimit = strchr(corename, ' ');
1783                 if (delimit)
1784                         *delimit = '\0';
1785                 delimit = strrchr(helper_argv[0], '/');
1786                 if (delimit)
1787                         delimit++;
1788                 else
1789                         delimit = helper_argv[0];
1790                 if (!strcmp(delimit, current->comm)) {
1791                         printk(KERN_NOTICE "Recursive core dump detected, "
1792                                         "aborting\n");
1793                         goto fail_unlock;
1794                 }
1795
1796                 core_limit = RLIM_INFINITY;
1797
1798                 /* SIGPIPE can happen, but it's just never processed */
1799                 if (call_usermodehelper_pipe(corename+1, helper_argv, NULL,
1800                                 &file)) {
1801                         printk(KERN_INFO "Core dump to %s pipe failed\n",
1802                                corename);
1803                         goto fail_unlock;
1804                 }
1805         } else
1806                 file = filp_open(corename,
1807                                  O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
1808                                  0600);
1809         if (IS_ERR(file))
1810                 goto fail_unlock;
1811         inode = file->f_path.dentry->d_inode;
1812         if (inode->i_nlink > 1)
1813                 goto close_fail;        /* multiple links - don't dump */
1814         if (!ispipe && d_unhashed(file->f_path.dentry))
1815                 goto close_fail;
1816
1817         /* AK: actually i see no reason to not allow this for named pipes etc.,
1818            but keep the previous behaviour for now. */
1819         if (!ispipe && !S_ISREG(inode->i_mode))
1820                 goto close_fail;
1821         /*
1822          * Dont allow local users get cute and trick others to coredump
1823          * into their pre-created files:
1824          */
1825         if (inode->i_uid != current_fsuid())
1826                 goto close_fail;
1827         if (!file->f_op)
1828                 goto close_fail;
1829         if (!file->f_op->write)
1830                 goto close_fail;
1831         if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0)
1832                 goto close_fail;
1833
1834         retval = binfmt->core_dump(signr, regs, file, core_limit);
1835
1836         if (retval)
1837                 current->signal->group_exit_code |= 0x80;
1838 close_fail:
1839         filp_close(file, NULL);
1840 fail_unlock:
1841         if (helper_argv)
1842                 argv_free(helper_argv);
1843
1844         revert_creds(old_cred);
1845         put_cred(cred);
1846         coredump_finish(mm);
1847 fail:
1848         return retval;
1849 }