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/syscalls.h>
  50 #include <linux/tsacct_kern.h>
  51 #include <linux/cn_proc.h>
  52 #include <linux/audit.h>
  53 #include <linux/tracehook.h>
  54 #include <linux/kmod.h>
  55 #include <linux/fsnotify.h>
  56 #include <linux/fs_struct.h>
  57 #include <linux/pipe_fs_i.h>
  58 #include <trace/fs.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 /*
  76  * Also used in compat.c.
  77  */
  78 DEFINE_TRACE(fs_exec);
  79
  80 int __register_binfmt(struct linux_binfmt * fmt, int insert)
  81 {
  82         if (!fmt)
  83                 return -EINVAL;
  84         write_lock(&binfmt_lock);
  85         insert ? list_add(&fmt->lh, &formats) :
  86                  list_add_tail(&fmt->lh, &formats);
  87         write_unlock(&binfmt_lock);
  88         return 0;
  89 }
  90
  91 EXPORT_SYMBOL(__register_binfmt);
  92
  93 void unregister_binfmt(struct linux_binfmt * fmt)
  94 {
  95         write_lock(&binfmt_lock);
  96         list_del(&fmt->lh);
  97         write_unlock(&binfmt_lock);
  98 }
  99
 100 EXPORT_SYMBOL(unregister_binfmt);
 101
 102 static inline void put_binfmt(struct linux_binfmt * fmt)
 103 {
 104         module_put(fmt->module);
 105 }
 106
 107 /*
 108  * Note that a shared library must be both readable and executable due to
 109  * security reasons.
 110  *
 111  * Also note that we take the address to load from from the file itself.
 112  */
 113 SYSCALL_DEFINE1(uselib, const char __user *, library)
 114 {
 115         struct file *file;
 116         char *tmp = getname(library);
 117         int error = PTR_ERR(tmp);
 118
 119         if (IS_ERR(tmp))
 120                 goto out;
 121
 122         file = do_filp_open(AT_FDCWD, tmp,
 123                                 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0,
 124                                 MAY_READ | MAY_EXEC | MAY_OPEN);
 125         putname(tmp);
 126         error = PTR_ERR(file);
 127         if (IS_ERR(file))
 128                 goto out;
 129
 130         error = -EINVAL;
 131         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
 132                 goto exit;
 133
 134         error = -EACCES;
 135         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 136                 goto exit;
 137
 138         fsnotify_open(file->f_path.dentry);
 139
 140         error = -ENOEXEC;
 141         if(file->f_op) {
 142                 struct linux_binfmt * fmt;
 143
 144                 read_lock(&binfmt_lock);
 145                 list_for_each_entry(fmt, &formats, lh) {
 146                         if (!fmt->load_shlib)
 147                                 continue;
 148                         if (!try_module_get(fmt->module))
 149                                 continue;
 150                         read_unlock(&binfmt_lock);
 151                         error = fmt->load_shlib(file);
 152                         read_lock(&binfmt_lock);
 153                         put_binfmt(fmt);
 154                         if (error != -ENOEXEC)
 155                                 break;
 156                 }
 157                 read_unlock(&binfmt_lock);
 158         }
 159 exit:
 160         fput(file);
 161 out:
 162         return error;
 163 }
 164
 165 #ifdef CONFIG_MMU
 166
 167 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 168                 int write)
 169 {
 170         struct page *page;
 171         int ret;
 172
 173 #ifdef CONFIG_STACK_GROWSUP
 174         if (write) {
 175                 ret = expand_stack_downwards(bprm->vma, pos);
 176                 if (ret < 0)
 177                         return NULL;
 178         }
 179 #endif
 180         ret = get_user_pages(current, bprm->mm, pos,
 181                         1, write, 1, &page, NULL);
 182         if (ret <= 0)
 183                 return NULL;
 184
 185         if (write) {
 186                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 187                 struct rlimit *rlim;
 188
 189                 /*
 190                  * We've historically supported up to 32 pages (ARG_MAX)
 191                  * of argument strings even with small stacks
 192                  */
 193                 if (size <= ARG_MAX)
 194                         return page;
 195
 196                 /*
 197                  * Limit to 1/4-th the stack size for the argv+env strings.
 198                  * This ensures that:
 199                  *  - the remaining binfmt code will not run out of stack space,
 200                  *  - the program will have a reasonable amount of stack left
 201                  *    to work from.
 202                  */
 203                 rlim = current->signal->rlim;
 204                 if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
 205                         put_page(page);
 206                         return NULL;
 207                 }
 208         }
 209
 210         return page;
 211 }
 212
 213 static void put_arg_page(struct page *page)
 214 {
 215         put_page(page);
 216 }
 217
 218 static void free_arg_page(struct linux_binprm *bprm, int i)
 219 {
 220 }
 221
 222 static void free_arg_pages(struct linux_binprm *bprm)
 223 {
 224 }
 225
 226 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 227                 struct page *page)
 228 {
 229         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 230 }
 231
 232 static int __bprm_mm_init(struct linux_binprm *bprm)
 233 {
 234         int err;
 235         struct vm_area_struct *vma = NULL;
 236         struct mm_struct *mm = bprm->mm;
 237
 238         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 239         if (!vma)
 240                 return -ENOMEM;
 241
 242         down_write(&mm->mmap_sem);
 243         vma->vm_mm = mm;
 244
 245         /*
 246          * Place the stack at the largest stack address the architecture
 247          * supports. Later, we'll move this to an appropriate place. We don't
 248          * use STACK_TOP because that can depend on attributes which aren't
 249          * configured yet.
 250          */
 251         vma->vm_end = STACK_TOP_MAX;
 252         vma->vm_start = vma->vm_end - PAGE_SIZE;
 253         vma->vm_flags = VM_STACK_FLAGS;
 254         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 255         err = insert_vm_struct(mm, vma);
 256         if (err)
 257                 goto err;
 258
 259         mm->stack_vm = mm->total_vm = 1;
 260         up_write(&mm->mmap_sem);
 261         bprm->p = vma->vm_end - sizeof(void *);
 262         return 0;
 263 err:
 264         up_write(&mm->mmap_sem);
 265         bprm->vma = NULL;
 266         kmem_cache_free(vm_area_cachep, vma);
 267         return err;
 268 }
 269
 270 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 271 {
 272         return len <= MAX_ARG_STRLEN;
 273 }
 274
 275 #else
 276
 277 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 278                 int write)
 279 {
 280         struct page *page;
 281
 282         page = bprm->page[pos / PAGE_SIZE];
 283         if (!page && write) {
 284                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 285                 if (!page)
 286                         return NULL;
 287                 bprm->page[pos / PAGE_SIZE] = page;
 288         }
 289
 290         return page;
 291 }
 292
 293 static void put_arg_page(struct page *page)
 294 {
 295 }
 296
 297 static void free_arg_page(struct linux_binprm *bprm, int i)
 298 {
 299         if (bprm->page[i]) {
 300                 __free_page(bprm->page[i]);
 301                 bprm->page[i] = NULL;
 302         }
 303 }
 304
 305 static void free_arg_pages(struct linux_binprm *bprm)
 306 {
 307         int i;
 308
 309         for (i = 0; i < MAX_ARG_PAGES; i++)
 310                 free_arg_page(bprm, i);
 311 }
 312
 313 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 314                 struct page *page)
 315 {
 316 }
 317
 318 static int __bprm_mm_init(struct linux_binprm *bprm)
 319 {
 320         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 321         return 0;
 322 }
 323
 324 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 325 {
 326         return len <= bprm->p;
 327 }
 328
 329 #endif /* CONFIG_MMU */
 330
 331 /*
 332  * Create a new mm_struct and populate it with a temporary stack
 333  * vm_area_struct.  We don't have enough context at this point to set the stack
 334  * flags, permissions, and offset, so we use temporary values.  We'll update
 335  * them later in setup_arg_pages().
 336  */
 337 int bprm_mm_init(struct linux_binprm *bprm)
 338 {
 339         int err;
 340         struct mm_struct *mm = NULL;
 341
 342         bprm->mm = mm = mm_alloc();
 343         err = -ENOMEM;
 344         if (!mm)
 345                 goto err;
 346
 347         err = init_new_context(current, mm);
 348         if (err)
 349                 goto err;
 350
 351         err = __bprm_mm_init(bprm);
 352         if (err)
 353                 goto err;
 354
 355         return 0;
 356
 357 err:
 358         if (mm) {
 359                 bprm->mm = NULL;
 360                 mmdrop(mm);
 361         }
 362
 363         return err;
 364 }
 365
 366 /*
 367  * count() counts the number of strings in array ARGV.
 368  */
 369 static int count(char __user * __user * argv, int max)
 370 {
 371         int i = 0;
 372
 373         if (argv != NULL) {
 374                 for (;;) {
 375                         char __user * p;
 376
 377                         if (get_user(p, argv))
 378                                 return -EFAULT;
 379                         if (!p)
 380                                 break;
 381                         argv++;
 382                         if (i++ >= max)
 383                                 return -E2BIG;
 384                         cond_resched();
 385                 }
 386         }
 387         return i;
 388 }
 389
 390 /*
 391  * 'copy_strings()' copies argument/environment strings from the old
 392  * processes's memory to the new process's stack.  The call to get_user_pages()
 393  * ensures the destination page is created and not swapped out.
 394  */
 395 static int copy_strings(int argc, char __user * __user * argv,
 396                         struct linux_binprm *bprm)
 397 {
 398         struct page *kmapped_page = NULL;
 399         char *kaddr = NULL;
 400         unsigned long kpos = 0;
 401         int ret;
 402
 403         while (argc-- > 0) {
 404                 char __user *str;
 405                 int len;
 406                 unsigned long pos;
 407
 408                 if (get_user(str, argv+argc) ||
 409                                 !(len = strnlen_user(str, MAX_ARG_STRLEN))) {
 410                         ret = -EFAULT;
 411                         goto out;
 412                 }
 413
 414                 if (!valid_arg_len(bprm, len)) {
 415                         ret = -E2BIG;
 416                         goto out;
 417                 }
 418
 419                 /* We're going to work our way backwords. */
 420                 pos = bprm->p;
 421                 str += len;
 422                 bprm->p -= len;
 423
 424                 while (len > 0) {
 425                         int offset, bytes_to_copy;
 426
 427                         offset = pos % PAGE_SIZE;
 428                         if (offset == 0)
 429                                 offset = PAGE_SIZE;
 430
 431                         bytes_to_copy = offset;
 432                         if (bytes_to_copy > len)
 433                                 bytes_to_copy = len;
 434
 435                         offset -= bytes_to_copy;
 436                         pos -= bytes_to_copy;
 437                         str -= bytes_to_copy;
 438                         len -= bytes_to_copy;
 439
 440                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 441                                 struct page *page;
 442
 443                                 page = get_arg_page(bprm, pos, 1);
 444                                 if (!page) {
 445                                         ret = -E2BIG;
 446                                         goto out;
 447                                 }
 448
 449                                 if (kmapped_page) {
 450                                         flush_kernel_dcache_page(kmapped_page);
 451                                         kunmap(kmapped_page);
 452                                         put_arg_page(kmapped_page);
 453                                 }
 454                                 kmapped_page = page;
 455                                 kaddr = kmap(kmapped_page);
 456                                 kpos = pos & PAGE_MASK;
 457                                 flush_arg_page(bprm, kpos, kmapped_page);
 458                         }
 459                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 460                                 ret = -EFAULT;
 461                                 goto out;
 462                         }
 463                 }
 464         }
 465         ret = 0;
 466 out:
 467         if (kmapped_page) {
 468                 flush_kernel_dcache_page(kmapped_page);
 469                 kunmap(kmapped_page);
 470                 put_arg_page(kmapped_page);
 471         }
 472         return ret;
 473 }
 474
 475 /*
 476  * Like copy_strings, but get argv and its values from kernel memory.
 477  */
 478 int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm)
 479 {
 480         int r;
 481         mm_segment_t oldfs = get_fs();
 482         set_fs(KERNEL_DS);
 483         r = copy_strings(argc, (char __user * __user *)argv, bprm);
 484         set_fs(oldfs);
 485         return r;
 486 }
 487 EXPORT_SYMBOL(copy_strings_kernel);
 488
 489 #ifdef CONFIG_MMU
 490
 491 /*
 492  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 493  * the binfmt code determines where the new stack should reside, we shift it to
 494  * its final location.  The process proceeds as follows:
 495  *
 496  * 1) Use shift to calculate the new vma endpoints.
 497  * 2) Extend vma to cover both the old and new ranges.  This ensures the
 498  *    arguments passed to subsequent functions are consistent.
 499  * 3) Move vma's page tables to the new range.
 500  * 4) Free up any cleared pgd range.
 501  * 5) Shrink the vma to cover only the new range.
 502  */
 503 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 504 {
 505         struct mm_struct *mm = vma->vm_mm;
 506         unsigned long old_start = vma->vm_start;
 507         unsigned long old_end = vma->vm_end;
 508         unsigned long length = old_end - old_start;
 509         unsigned long new_start = old_start - shift;
 510         unsigned long new_end = old_end - shift;
 511         struct mmu_gather *tlb;
 512
 513         BUG_ON(new_start > new_end);
 514
 515         /*
 516          * ensure there are no vmas between where we want to go
 517          * and where we are
 518          */
 519         if (vma != find_vma(mm, new_start))
 520                 return -EFAULT;
 521
 522         /*
 523          * cover the whole range: [new_start, old_end)
 524          */
 525         vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);
 526
 527         /*
 528          * move the page tables downwards, on failure we rely on
 529          * process cleanup to remove whatever mess we made.
 530          */
 531         if (length != move_page_tables(vma, old_start,
 532                                        vma, new_start, length))
 533                 return -ENOMEM;
 534
 535         lru_add_drain();
 536         tlb = tlb_gather_mmu(mm, 0);
 537         if (new_end > old_start) {
 538                 /*
 539                  * when the old and new regions overlap clear from new_end.
 540                  */
 541                 free_pgd_range(tlb, new_end, old_end, new_end,
 542                         vma->vm_next ? vma->vm_next->vm_start : 0);
 543         } else {
 544                 /*
 545                  * otherwise, clean from old_start; this is done to not touch
 546                  * the address space in [new_end, old_start) some architectures
 547                  * have constraints on va-space that make this illegal (IA64) -
 548                  * for the others its just a little faster.
 549                  */
 550                 free_pgd_range(tlb, old_start, old_end, new_end,
 551                         vma->vm_next ? vma->vm_next->vm_start : 0);
 552         }
 553         tlb_finish_mmu(tlb, new_end, old_end);
 554
 555         /*
 556          * shrink the vma to just the new range.
 557          */
 558         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 559
 560         return 0;
 561 }
 562
 563 #define EXTRA_STACK_VM_PAGES    20      /* random */
 564
 565 /*
 566  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 567  * the stack is optionally relocated, and some extra space is added.
 568  */
 569 int setup_arg_pages(struct linux_binprm *bprm,
 570                     unsigned long stack_top,
 571                     int executable_stack)
 572 {
 573         unsigned long ret;
 574         unsigned long stack_shift;
 575         struct mm_struct *mm = current->mm;
 576         struct vm_area_struct *vma = bprm->vma;
 577         struct vm_area_struct *prev = NULL;
 578         unsigned long vm_flags;
 579         unsigned long stack_base;
 580         unsigned long stack_size;
 581         unsigned long stack_expand;
 582         unsigned long rlim_stack;
 583
 584 #ifdef CONFIG_STACK_GROWSUP
 585         /* Limit stack size to 1GB */
 586         stack_base = rlimit_max(RLIMIT_STACK);
 587         if (stack_base > (1 << 30))
 588                 stack_base = 1 << 30;
 589
 590         /* Make sure we didn't let the argument array grow too large. */
 591         if (vma->vm_end - vma->vm_start > stack_base)
 592                 return -ENOMEM;
 593
 594         stack_base = PAGE_ALIGN(stack_top - stack_base);
 595
 596         stack_shift = vma->vm_start - stack_base;
 597         mm->arg_start = bprm->p - stack_shift;
 598         bprm->p = vma->vm_end - stack_shift;
 599 #else
 600         stack_top = arch_align_stack(stack_top);
 601         stack_top = PAGE_ALIGN(stack_top);
 602         stack_shift = vma->vm_end - stack_top;
 603
 604         bprm->p -= stack_shift;
 605         mm->arg_start = bprm->p;
 606 #endif
 607
 608         if (bprm->loader)
 609                 bprm->loader -= stack_shift;
 610         bprm->exec -= stack_shift;
 611
 612         down_write(&mm->mmap_sem);
 613         vm_flags = VM_STACK_FLAGS;
 614
 615         /*
 616          * Adjust stack execute permissions; explicitly enable for
 617          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 618          * (arch default) otherwise.
 619          */
 620         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 621                 vm_flags |= VM_EXEC;
 622         else if (executable_stack == EXSTACK_DISABLE_X)
 623                 vm_flags &= ~VM_EXEC;
 624         vm_flags |= mm->def_flags;
 625
 626         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 627                         vm_flags);
 628         if (ret)
 629                 goto out_unlock;
 630         BUG_ON(prev != vma);
 631
 632         /* Move stack pages down in memory. */
 633         if (stack_shift) {
 634                 ret = shift_arg_pages(vma, stack_shift);
 635                 if (ret)
 636                         goto out_unlock;
 637         }
 638
 639         stack_expand = EXTRA_STACK_VM_PAGES * PAGE_SIZE;
 640         stack_size = vma->vm_end - vma->vm_start;
 641         /*
 642          * Align this down to a page boundary as expand_stack
 643          * will align it up.
 644          */
 645         rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 646 #ifdef CONFIG_STACK_GROWSUP
 647         if (stack_size + stack_expand > rlim_stack)
 648                 stack_base = vma->vm_start + rlim_stack;
 649         else
 650                 stack_base = vma->vm_end + stack_expand;
 651 #else
 652         if (stack_size + stack_expand > rlim_stack)
 653                 stack_base = vma->vm_end - rlim_stack;
 654         else
 655                 stack_base = vma->vm_start - stack_expand;
 656 #endif
 657         ret = expand_stack(vma, stack_base);
 658         if (ret)
 659                 ret = -EFAULT;
 660
 661 out_unlock:
 662         up_write(&mm->mmap_sem);
 663         return ret;
 664 }
 665 EXPORT_SYMBOL(setup_arg_pages);
 666
 667 #endif /* CONFIG_MMU */
 668
 669 struct file *open_exec(const char *name)
 670 {
 671         struct file *file;
 672         int err;
 673
 674         file = do_filp_open(AT_FDCWD, name,
 675                                 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0,
 676                                 MAY_EXEC | MAY_OPEN);
 677         if (IS_ERR(file))
 678                 goto out;
 679
 680         err = -EACCES;
 681         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
 682                 goto exit;
 683
 684         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 685                 goto exit;
 686
 687         fsnotify_open(file->f_path.dentry);
 688
 689         if (file->f_op && file->f_op->open_exec) {
 690                 err = file->f_op->open_exec(file->f_path.dentry->d_inode);
 691                 if (err)
 692                         goto exit;
 693         }
 694
 695         err = deny_write_access(file);
 696         if (err)
 697                 goto exit;
 698
 699 out:
 700         return file;
 701
 702 exit:
 703         fput(file);
 704         return ERR_PTR(err);
 705 }
 706 EXPORT_SYMBOL(open_exec);
 707
 708 int kernel_read(struct file *file, loff_t 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
 858                 list_replace_rcu(&leader->tasks, &tsk->tasks);
 859                 list_replace_init(&leader->sibling, &tsk->sibling);
 860
 861                 tsk->group_leader = tsk;
 862                 leader->group_leader = tsk;
 863
 864                 tsk->exit_signal = SIGCHLD;
 865
 866                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 867                 leader->exit_state = EXIT_DEAD;
 868                 write_unlock_irq(&tasklist_lock);
 869
 870                 release_task(leader);
 871         }
 872
 873         sig->group_exit_task = NULL;
 874         sig->notify_count = 0;
 875
 876 no_thread_group:
 877         if (current->mm)
 878                 setmax_mm_hiwater_rss(&sig->maxrss, current->mm);
 879
 880         exit_itimers(sig);
 881         flush_itimer_signals();
 882
 883         if (atomic_read(&oldsighand->count) != 1) {
 884                 struct sighand_struct *newsighand;
 885                 /*
 886                  * This ->sighand is shared with the CLONE_SIGHAND
 887                  * but not CLONE_THREAD task, switch to the new one.
 888                  */
 889                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 890                 if (!newsighand)
 891                         return -ENOMEM;
 892
 893                 atomic_set(&newsighand->count, 1);
 894                 memcpy(newsighand->action, oldsighand->action,
 895                        sizeof(newsighand->action));
 896
 897                 write_lock_irq(&tasklist_lock);
 898                 spin_lock(&oldsighand->siglock);
 899                 rcu_assign_pointer(tsk->sighand, newsighand);
 900                 spin_unlock(&oldsighand->siglock);
 901                 write_unlock_irq(&tasklist_lock);
 902
 903                 __cleanup_sighand(oldsighand);
 904         }
 905
 906         BUG_ON(!thread_group_leader(tsk));
 907         return 0;
 908 }
 909
 910 /*
 911  * These functions flushes out all traces of the currently running executable
 912  * so that a new one can be started
 913  */
 914 static void flush_old_files(struct files_struct * files)
 915 {
 916         long j = -1;
 917         struct fdtable *fdt;
 918
 919         spin_lock(&files->file_lock);
 920         for (;;) {
 921                 unsigned long set, i;
 922
 923                 j++;
 924                 i = j * __NFDBITS;
 925                 fdt = files_fdtable(files);
 926                 if (i >= fdt->max_fds)
 927                         break;
 928                 set = fdt->close_on_exec->fds_bits[j];
 929                 if (!set)
 930                         continue;
 931                 fdt->close_on_exec->fds_bits[j] = 0;
 932                 spin_unlock(&files->file_lock);
 933                 for ( ; set ; i++,set >>= 1) {
 934                         if (set & 1) {
 935                                 sys_close(i);
 936                         }
 937                 }
 938                 spin_lock(&files->file_lock);
 939
 940         }
 941         spin_unlock(&files->file_lock);
 942 }
 943
 944 char *get_task_comm(char *buf, struct task_struct *tsk)
 945 {
 946         /* buf must be at least sizeof(tsk->comm) in size */
 947         task_lock(tsk);
 948         strncpy(buf, tsk->comm, sizeof(tsk->comm));
 949         task_unlock(tsk);
 950         return buf;
 951 }
 952
 953 void set_task_comm(struct task_struct *tsk, char *buf)
 954 {
 955         task_lock(tsk);
 956
 957         /*
 958          * Threads may access current->comm without holding
 959          * the task lock, so write the string carefully.
 960          * Readers without a lock may see incomplete new
 961          * names but are safe from non-terminating string reads.
 962          */
 963         memset(tsk->comm, 0, TASK_COMM_LEN);
 964         wmb();
 965         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
 966         task_unlock(tsk);
 967         perf_event_comm(tsk);
 968 }
 969
 970 int flush_old_exec(struct linux_binprm * bprm)
 971 {
 972         int retval;
 973
 974         /*
 975          * Make sure we have a private signal table and that
 976          * we are unassociated from the previous thread group.
 977          */
 978         retval = de_thread(current);
 979         if (retval)
 980                 goto out;
 981
 982         set_mm_exe_file(bprm->mm, bprm->file);
 983
 984         /*
 985          * Release all of the old mmap stuff
 986          */
 987         retval = exec_mmap(bprm->mm);
 988         if (retval)
 989                 goto out;
 990
 991         bprm->mm = NULL;                /* We're using it now */
 992
 993         current->flags &= ~PF_RANDOMIZE;
 994         flush_thread();
 995         current->personality &= ~bprm->per_clear;
 996
 997         return 0;
 998
 999 out:
1000         return retval;
1001 }
1002 EXPORT_SYMBOL(flush_old_exec);
1003
1004 void setup_new_exec(struct linux_binprm * bprm)
1005 {
1006         int i, ch;
1007         char * name;
1008         char tcomm[sizeof(current->comm)];
1009
1010         arch_pick_mmap_layout(current->mm);
1011
1012         /* This is the point of no return */
1013         current->sas_ss_sp = current->sas_ss_size = 0;
1014
1015         if (current_euid() == current_uid() && current_egid() == current_gid())
1016                 set_dumpable(current->mm, 1);
1017         else
1018                 set_dumpable(current->mm, suid_dumpable);
1019
1020         name = bprm->filename;
1021
1022         /* Copies the binary name from after last slash */
1023         for (i=0; (ch = *(name++)) != '\0';) {
1024                 if (ch == '/')
1025                         i = 0; /* overwrite what we wrote */
1026                 else
1027                         if (i < (sizeof(tcomm) - 1))
1028                                 tcomm[i++] = ch;
1029         }
1030         tcomm[i] = '\0';
1031         set_task_comm(current, tcomm);
1032
1033         /* Set the new mm task size. We have to do that late because it may
1034          * depend on TIF_32BIT which is only updated in flush_thread() on
1035          * some architectures like powerpc
1036          */
1037         current->mm->task_size = TASK_SIZE;
1038
1039         /* install the new credentials */
1040         if (bprm->cred->uid != current_euid() ||
1041             bprm->cred->gid != current_egid()) {
1042                 current->pdeath_signal = 0;
1043         } else if (file_permission(bprm->file, MAY_READ) ||
1044                    bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) {
1045                 set_dumpable(current->mm, suid_dumpable);
1046         }
1047
1048         /*
1049          * Flush performance counters when crossing a
1050          * security domain:
1051          */
1052         if (!get_dumpable(current->mm))
1053                 perf_event_exit_task(current);
1054
1055         /* An exec changes our domain. We are no longer part of the thread
1056            group */
1057
1058         current->self_exec_id++;
1059
1060         flush_signal_handlers(current, 0);
1061         flush_old_files(current->files);
1062 }
1063 EXPORT_SYMBOL(setup_new_exec);
1064
1065 /*
1066  * Prepare credentials and lock ->cred_guard_mutex.
1067  * install_exec_creds() commits the new creds and drops the lock.
1068  * Or, if exec fails before, free_bprm() should release ->cred and
1069  * and unlock.
1070  */
1071 int prepare_bprm_creds(struct linux_binprm *bprm)
1072 {
1073         if (mutex_lock_interruptible(&current->cred_guard_mutex))
1074                 return -ERESTARTNOINTR;
1075
1076         bprm->cred = prepare_exec_creds();
1077         if (likely(bprm->cred))
1078                 return 0;
1079
1080         mutex_unlock(&current->cred_guard_mutex);
1081         return -ENOMEM;
1082 }
1083
1084 void free_bprm(struct linux_binprm *bprm)
1085 {
1086         free_arg_pages(bprm);
1087         if (bprm->cred) {
1088                 mutex_unlock(&current->cred_guard_mutex);
1089                 abort_creds(bprm->cred);
1090         }
1091         kfree(bprm);
1092 }
1093
1094 /*
1095  * install the new credentials for this executable
1096  */
1097 void install_exec_creds(struct linux_binprm *bprm)
1098 {
1099         security_bprm_committing_creds(bprm);
1100
1101         commit_creds(bprm->cred);
1102         bprm->cred = NULL;
1103         /*
1104          * cred_guard_mutex must be held at least to this point to prevent
1105          * ptrace_attach() from altering our determination of the task's
1106          * credentials; any time after this it may be unlocked.
1107          */
1108         security_bprm_committed_creds(bprm);
1109         mutex_unlock(&current->cred_guard_mutex);
1110 }
1111 EXPORT_SYMBOL(install_exec_creds);
1112
1113 /*
1114  * determine how safe it is to execute the proposed program
1115  * - the caller must hold current->cred_guard_mutex to protect against
1116  *   PTRACE_ATTACH
1117  */
1118 int check_unsafe_exec(struct linux_binprm *bprm)
1119 {
1120         struct task_struct *p = current, *t;
1121         unsigned n_fs;
1122         int res = 0;
1123
1124         bprm->unsafe = tracehook_unsafe_exec(p);
1125
1126         n_fs = 1;
1127         write_lock(&p->fs->lock);
1128         rcu_read_lock();
1129         for (t = next_thread(p); t != p; t = next_thread(t)) {
1130                 if (t->fs == p->fs)
1131                         n_fs++;
1132         }
1133         rcu_read_unlock();
1134
1135         if (p->fs->users > n_fs) {
1136                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1137         } else {
1138                 res = -EAGAIN;
1139                 if (!p->fs->in_exec) {
1140                         p->fs->in_exec = 1;
1141                         res = 1;
1142                 }
1143         }
1144         write_unlock(&p->fs->lock);
1145
1146         return res;
1147 }
1148
1149 /*
1150  * Fill the binprm structure from the inode.
1151  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1152  *
1153  * This may be called multiple times for binary chains (scripts for example).
1154  */
1155 int prepare_binprm(struct linux_binprm *bprm)
1156 {
1157         umode_t mode;
1158         struct inode * inode = bprm->file->f_path.dentry->d_inode;
1159         int retval;
1160
1161         mode = inode->i_mode;
1162         if (bprm->file->f_op == NULL)
1163                 return -EACCES;
1164
1165         /* clear any previous set[ug]id data from a previous binary */
1166         bprm->cred->euid = current_euid();
1167         bprm->cred->egid = current_egid();
1168
1169         if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1170                 /* Set-uid? */
1171                 if (mode & S_ISUID) {
1172                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1173                         bprm->cred->euid = inode->i_uid;
1174                 }
1175
1176                 /* Set-gid? */
1177                 /*
1178                  * If setgid is set but no group execute bit then this
1179                  * is a candidate for mandatory locking, not a setgid
1180                  * executable.
1181                  */
1182                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1183                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1184                         bprm->cred->egid = inode->i_gid;
1185                 }
1186         }
1187
1188         /* fill in binprm security blob */
1189         retval = security_bprm_set_creds(bprm);
1190         if (retval)
1191                 return retval;
1192         bprm->cred_prepared = 1;
1193
1194         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1195         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1196 }
1197
1198 EXPORT_SYMBOL(prepare_binprm);
1199
1200 /*
1201  * Arguments are '\0' separated strings found at the location bprm->p
1202  * points to; chop off the first by relocating brpm->p to right after
1203  * the first '\0' encountered.
1204  */
1205 int remove_arg_zero(struct linux_binprm *bprm)
1206 {
1207         int ret = 0;
1208         unsigned long offset;
1209         char *kaddr;
1210         struct page *page;
1211
1212         if (!bprm->argc)
1213                 return 0;
1214
1215         do {
1216                 offset = bprm->p & ~PAGE_MASK;
1217                 page = get_arg_page(bprm, bprm->p, 0);
1218                 if (!page) {
1219                         ret = -EFAULT;
1220                         goto out;
1221                 }
1222                 kaddr = kmap_atomic(page, KM_USER0);
1223
1224                 for (; offset < PAGE_SIZE && kaddr[offset];
1225                                 offset++, bprm->p++)
1226                         ;
1227
1228                 kunmap_atomic(kaddr, KM_USER0);
1229                 put_arg_page(page);
1230
1231                 if (offset == PAGE_SIZE)
1232                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1233         } while (offset == PAGE_SIZE);
1234
1235         bprm->p++;
1236         bprm->argc--;
1237         ret = 0;
1238
1239 out:
1240         return ret;
1241 }
1242 EXPORT_SYMBOL(remove_arg_zero);
1243
1244 /*
1245  * cycle the list of binary formats handler, until one recognizes the image
1246  */
1247 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1248 {
1249         unsigned int depth = bprm->recursion_depth;
1250         int try,retval;
1251         struct linux_binfmt *fmt;
1252
1253         retval = security_bprm_check(bprm);
1254         if (retval)
1255                 return retval;
1256
1257         /* kernel module loader fixup */
1258         /* so we don't try to load run modprobe in kernel space. */
1259         set_fs(USER_DS);
1260
1261         retval = audit_bprm(bprm);
1262         if (retval)
1263                 return retval;
1264
1265         retval = -ENOENT;
1266         for (try=0; try<2; try++) {
1267                 read_lock(&binfmt_lock);
1268                 list_for_each_entry(fmt, &formats, lh) {
1269                         int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1270                         if (!fn)
1271                                 continue;
1272                         if (!try_module_get(fmt->module))
1273                                 continue;
1274                         read_unlock(&binfmt_lock);
1275                         retval = fn(bprm, regs);
1276                         /*
1277                          * Restore the depth counter to its starting value
1278                          * in this call, so we don't have to rely on every
1279                          * load_binary function to restore it on return.
1280                          */
1281                         bprm->recursion_depth = depth;
1282                         if (retval >= 0) {
1283                                 if (depth == 0)
1284                                         tracehook_report_exec(fmt, bprm, regs);
1285                                 put_binfmt(fmt);
1286                                 allow_write_access(bprm->file);
1287                                 if (bprm->file)
1288                                         fput(bprm->file);
1289                                 bprm->file = NULL;
1290                                 current->did_exec = 1;
1291                                 proc_exec_connector(current);
1292                                 return retval;
1293                         }
1294                         read_lock(&binfmt_lock);
1295                         put_binfmt(fmt);
1296                         if (retval != -ENOEXEC || bprm->mm == NULL)
1297                                 break;
1298                         if (!bprm->file) {
1299                                 read_unlock(&binfmt_lock);
1300                                 return retval;
1301                         }
1302                 }
1303                 read_unlock(&binfmt_lock);
1304                 if (retval != -ENOEXEC || bprm->mm == NULL) {
1305                         break;
1306 #ifdef CONFIG_MODULES
1307                 } else {
1308 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1309                         if (printable(bprm->buf[0]) &&
1310                             printable(bprm->buf[1]) &&
1311                             printable(bprm->buf[2]) &&
1312                             printable(bprm->buf[3]))
1313                                 break; /* -ENOEXEC */
1314                         request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1315 #endif
1316                 }
1317         }
1318         return retval;
1319 }
1320
1321 EXPORT_SYMBOL(search_binary_handler);
1322
1323 /*
1324  * sys_execve() executes a new program.
1325  */
1326 int do_execve(char * filename,
1327         char __user *__user *argv,
1328         char __user *__user *envp,
1329         struct pt_regs * regs)
1330 {
1331         struct linux_binprm *bprm;
1332         struct file *file;
1333         struct files_struct *displaced;
1334         bool clear_in_exec;
1335         int retval;
1336
1337         retval = unshare_files(&displaced);
1338         if (retval)
1339                 goto out_ret;
1340
1341         retval = -ENOMEM;
1342         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1343         if (!bprm)
1344                 goto out_files;
1345
1346         retval = prepare_bprm_creds(bprm);
1347         if (retval)
1348                 goto out_free;
1349
1350         retval = check_unsafe_exec(bprm);
1351         if (retval < 0)
1352                 goto out_free;
1353         clear_in_exec = retval;
1354         current->in_execve = 1;
1355
1356         file = open_exec(filename);
1357         retval = PTR_ERR(file);
1358         if (IS_ERR(file))
1359                 goto out_unmark;
1360
1361         sched_exec();
1362
1363         bprm->file = file;
1364         bprm->filename = filename;
1365         bprm->interp = filename;
1366
1367         retval = bprm_mm_init(bprm);
1368         if (retval)
1369                 goto out_file;
1370
1371         bprm->argc = count(argv, MAX_ARG_STRINGS);
1372         if ((retval = bprm->argc) < 0)
1373                 goto out;
1374
1375         bprm->envc = count(envp, MAX_ARG_STRINGS);
1376         if ((retval = bprm->envc) < 0)
1377                 goto out;
1378
1379         retval = prepare_binprm(bprm);
1380         if (retval < 0)
1381                 goto out;
1382
1383         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1384         if (retval < 0)
1385                 goto out;
1386
1387         bprm->exec = bprm->p;
1388         retval = copy_strings(bprm->envc, envp, bprm);
1389         if (retval < 0)
1390                 goto out;
1391
1392         retval = copy_strings(bprm->argc, argv, bprm);
1393         if (retval < 0)
1394                 goto out;
1395
1396         current->flags &= ~PF_KTHREAD;
1397         retval = search_binary_handler(bprm,regs);
1398         if (retval < 0)
1399                 goto out;
1400
1401         current->stack_start = current->mm->start_stack;
1402
1403         trace_fs_exec(filename);
1404         /* execve succeeded */
1405         current->fs->in_exec = 0;
1406         current->in_execve = 0;
1407         acct_update_integrals(current);
1408         free_bprm(bprm);
1409         if (displaced)
1410                 put_files_struct(displaced);
1411         return retval;
1412
1413 out:
1414         if (bprm->mm)
1415                 mmput (bprm->mm);
1416
1417 out_file:
1418         if (bprm->file) {
1419                 allow_write_access(bprm->file);
1420                 fput(bprm->file);
1421         }
1422
1423 out_unmark:
1424         if (clear_in_exec)
1425                 current->fs->in_exec = 0;
1426         current->in_execve = 0;
1427
1428 out_free:
1429         free_bprm(bprm);
1430
1431 out_files:
1432         if (displaced)
1433                 reset_files_struct(displaced);
1434 out_ret:
1435         return retval;
1436 }
1437
1438 void set_binfmt(struct linux_binfmt *new)
1439 {
1440         struct mm_struct *mm = current->mm;
1441
1442         if (mm->binfmt)
1443                 module_put(mm->binfmt->module);
1444
1445         mm->binfmt = new;
1446         if (new)
1447                 __module_get(new->module);
1448 }
1449
1450 EXPORT_SYMBOL(set_binfmt);
1451
1452 /* format_corename will inspect the pattern parameter, and output a
1453  * name into corename, which must have space for at least
1454  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1455  */
1456 static int format_corename(char *corename, long signr)
1457 {
1458         const struct cred *cred = current_cred();
1459         const char *pat_ptr = core_pattern;
1460         int ispipe = (*pat_ptr == '|');
1461         char *out_ptr = corename;
1462         char *const out_end = corename + CORENAME_MAX_SIZE;
1463         int rc;
1464         int pid_in_pattern = 0;
1465
1466         /* Repeat as long as we have more pattern to process and more output
1467            space */
1468         while (*pat_ptr) {
1469                 if (*pat_ptr != '%') {
1470                         if (out_ptr == out_end)
1471                                 goto out;
1472                         *out_ptr++ = *pat_ptr++;
1473                 } else {
1474                         switch (*++pat_ptr) {
1475                         case 0:
1476                                 goto out;
1477                         /* Double percent, output one percent */
1478                         case '%':
1479                                 if (out_ptr == out_end)
1480                                         goto out;
1481                                 *out_ptr++ = '%';
1482                                 break;
1483                         /* pid */
1484                         case 'p':
1485                                 pid_in_pattern = 1;
1486                                 rc = snprintf(out_ptr, out_end - out_ptr,
1487                                               "%d", task_tgid_vnr(current));
1488                                 if (rc > out_end - out_ptr)
1489                                         goto out;
1490                                 out_ptr += rc;
1491                                 break;
1492                         /* uid */
1493                         case 'u':
1494                                 rc = snprintf(out_ptr, out_end - out_ptr,
1495                                               "%d", cred->uid);
1496                                 if (rc > out_end - out_ptr)
1497                                         goto out;
1498                                 out_ptr += rc;
1499                                 break;
1500                         /* gid */
1501                         case 'g':
1502                                 rc = snprintf(out_ptr, out_end - out_ptr,
1503                                               "%d", cred->gid);
1504                                 if (rc > out_end - out_ptr)
1505                                         goto out;
1506                                 out_ptr += rc;
1507                                 break;
1508                         /* signal that caused the coredump */
1509                         case 's':
1510                                 rc = snprintf(out_ptr, out_end - out_ptr,
1511                                               "%ld", signr);
1512                                 if (rc > out_end - out_ptr)
1513                                         goto out;
1514                                 out_ptr += rc;
1515                                 break;
1516                         /* UNIX time of coredump */
1517                         case 't': {
1518                                 struct timeval tv;
1519                                 do_gettimeofday(&tv);
1520                                 rc = snprintf(out_ptr, out_end - out_ptr,
1521                                               "%lu", tv.tv_sec);
1522                                 if (rc > out_end - out_ptr)
1523                                         goto out;
1524                                 out_ptr += rc;
1525                                 break;
1526                         }
1527                         /* hostname */
1528                         case 'h':
1529                                 down_read(&uts_sem);
1530                                 rc = snprintf(out_ptr, out_end - out_ptr,
1531                                               "%s", utsname()->nodename);
1532                                 up_read(&uts_sem);
1533                                 if (rc > out_end - out_ptr)
1534                                         goto out;
1535                                 out_ptr += rc;
1536                                 break;
1537                         /* executable */
1538                         case 'e':
1539                                 rc = snprintf(out_ptr, out_end - out_ptr,
1540                                               "%s", current->comm);
1541                                 if (rc > out_end - out_ptr)
1542                                         goto out;
1543                                 out_ptr += rc;
1544                                 break;
1545                         /* core limit size */
1546                         case 'c':
1547                                 rc = snprintf(out_ptr, out_end - out_ptr,
1548                                         "%lu", rlimit(RLIMIT_CORE));
1549                                 if (rc > out_end - out_ptr)
1550                                         goto out;
1551                                 out_ptr += rc;
1552                                 break;
1553                         default:
1554                                 break;
1555                         }
1556                         ++pat_ptr;
1557                 }
1558         }
1559         /* Backward compatibility with core_uses_pid:
1560          *
1561          * If core_pattern does not include a %p (as is the default)
1562          * and core_uses_pid is set, then .%pid will be appended to
1563          * the filename. Do not do this for piped commands. */
1564         if (!ispipe && !pid_in_pattern && core_uses_pid) {
1565                 rc = snprintf(out_ptr, out_end - out_ptr,
1566                               ".%d", task_tgid_vnr(current));
1567                 if (rc > out_end - out_ptr)
1568                         goto out;
1569                 out_ptr += rc;
1570         }
1571 out:
1572         *out_ptr = 0;
1573         return ispipe;
1574 }
1575
1576 static int zap_process(struct task_struct *start)
1577 {
1578         struct task_struct *t;
1579         int nr = 0;
1580
1581         start->signal->flags = SIGNAL_GROUP_EXIT;
1582         start->signal->group_stop_count = 0;
1583
1584         t = start;
1585         do {
1586                 if (t != current && t->mm) {
1587                         sigaddset(&t->pending.signal, SIGKILL);
1588                         signal_wake_up(t, 1);
1589                         nr++;
1590                 }
1591         } while_each_thread(start, t);
1592
1593         return nr;
1594 }
1595
1596 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1597                                 struct core_state *core_state, int exit_code)
1598 {
1599         struct task_struct *g, *p;
1600         unsigned long flags;
1601         int nr = -EAGAIN;
1602
1603         spin_lock_irq(&tsk->sighand->siglock);
1604         if (!signal_group_exit(tsk->signal)) {
1605                 mm->core_state = core_state;
1606                 tsk->signal->group_exit_code = exit_code;
1607                 nr = zap_process(tsk);
1608         }
1609         spin_unlock_irq(&tsk->sighand->siglock);
1610         if (unlikely(nr < 0))
1611                 return nr;
1612
1613         if (atomic_read(&mm->mm_users) == nr + 1)
1614                 goto done;
1615         /*
1616          * We should find and kill all tasks which use this mm, and we should
1617          * count them correctly into ->nr_threads. We don't take tasklist
1618          * lock, but this is safe wrt:
1619          *
1620          * fork:
1621          *      None of sub-threads can fork after zap_process(leader). All
1622          *      processes which were created before this point should be
1623          *      visible to zap_threads() because copy_process() adds the new
1624          *      process to the tail of init_task.tasks list, and lock/unlock
1625          *      of ->siglock provides a memory barrier.
1626          *
1627          * do_exit:
1628          *      The caller holds mm->mmap_sem. This means that the task which
1629          *      uses this mm can't pass exit_mm(), so it can't exit or clear
1630          *      its ->mm.
1631          *
1632          * de_thread:
1633          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
1634          *      we must see either old or new leader, this does not matter.
1635          *      However, it can change p->sighand, so lock_task_sighand(p)
1636          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
1637          *      it can't fail.
1638          *
1639          *      Note also that "g" can be the old leader with ->mm == NULL
1640          *      and already unhashed and thus removed from ->thread_group.
1641          *      This is OK, __unhash_process()->list_del_rcu() does not
1642          *      clear the ->next pointer, we will find the new leader via
1643          *      next_thread().
1644          */
1645         rcu_read_lock();
1646         for_each_process(g) {
1647                 if (g == tsk->group_leader)
1648                         continue;
1649                 if (g->flags & PF_KTHREAD)
1650                         continue;
1651                 p = g;
1652                 do {
1653                         if (p->mm) {
1654                                 if (unlikely(p->mm == mm)) {
1655                                         lock_task_sighand(p, &flags);
1656                                         nr += zap_process(p);
1657                                         unlock_task_sighand(p, &flags);
1658                                 }
1659                                 break;
1660                         }
1661                 } while_each_thread(g, p);
1662         }
1663         rcu_read_unlock();
1664 done:
1665         atomic_set(&core_state->nr_threads, nr);
1666         return nr;
1667 }
1668
1669 static int coredump_wait(int exit_code, struct core_state *core_state)
1670 {
1671         struct task_struct *tsk = current;
1672         struct mm_struct *mm = tsk->mm;
1673         struct completion *vfork_done;
1674         int core_waiters;
1675
1676         init_completion(&core_state->startup);
1677         core_state->dumper.task = tsk;
1678         core_state->dumper.next = NULL;
1679         core_waiters = zap_threads(tsk, mm, core_state, exit_code);
1680         up_write(&mm->mmap_sem);
1681
1682         if (unlikely(core_waiters < 0))
1683                 goto fail;
1684
1685         /*
1686          * Make sure nobody is waiting for us to release the VM,
1687          * otherwise we can deadlock when we wait on each other
1688          */
1689         vfork_done = tsk->vfork_done;
1690         if (vfork_done) {
1691                 tsk->vfork_done = NULL;
1692                 complete(vfork_done);
1693         }
1694
1695         if (core_waiters)
1696                 wait_for_completion(&core_state->startup);
1697 fail:
1698         return core_waiters;
1699 }
1700
1701 static void coredump_finish(struct mm_struct *mm)
1702 {
1703         struct core_thread *curr, *next;
1704         struct task_struct *task;
1705
1706         next = mm->core_state->dumper.next;
1707         while ((curr = next) != NULL) {
1708                 next = curr->next;
1709                 task = curr->task;
1710                 /*
1711                  * see exit_mm(), curr->task must not see
1712                  * ->task == NULL before we read ->next.
1713                  */
1714                 smp_mb();
1715                 curr->task = NULL;
1716                 wake_up_process(task);
1717         }
1718
1719         mm->core_state = NULL;
1720 }
1721
1722 /*
1723  * set_dumpable converts traditional three-value dumpable to two flags and
1724  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1725  * these bits are not changed atomically.  So get_dumpable can observe the
1726  * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1727  * return either old dumpable or new one by paying attention to the order of
1728  * modifying the bits.
1729  *
1730  * dumpable |   mm->flags (binary)
1731  * old  new | initial interim  final
1732  * ---------+-----------------------
1733  *  0    1  |   00      01      01
1734  *  0    2  |   00      10(*)   11
1735  *  1    0  |   01      00      00
1736  *  1    2  |   01      11      11
1737  *  2    0  |   11      10(*)   00
1738  *  2    1  |   11      11      01
1739  *
1740  * (*) get_dumpable regards interim value of 10 as 11.
1741  */
1742 void set_dumpable(struct mm_struct *mm, int value)
1743 {
1744         switch (value) {
1745         case 0:
1746                 clear_bit(MMF_DUMPABLE, &mm->flags);
1747                 smp_wmb();
1748                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1749                 break;
1750         case 1:
1751                 set_bit(MMF_DUMPABLE, &mm->flags);
1752                 smp_wmb();
1753                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1754                 break;
1755         case 2:
1756                 set_bit(MMF_DUMP_SECURELY, &mm->flags);
1757                 smp_wmb();
1758                 set_bit(MMF_DUMPABLE, &mm->flags);
1759                 break;
1760         }
1761 }
1762
1763 int get_dumpable(struct mm_struct *mm)
1764 {
1765         int ret;
1766
1767         ret = mm->flags & 0x3;
1768         return (ret >= 2) ? 2 : ret;
1769 }
1770
1771 static void wait_for_dump_helpers(struct file *file)
1772 {
1773         struct pipe_inode_info *pipe;
1774
1775         pipe = file->f_path.dentry->d_inode->i_pipe;
1776
1777         pipe_lock(pipe);
1778         pipe->readers++;
1779         pipe->writers--;
1780
1781         while ((pipe->readers > 1) && (!signal_pending(current))) {
1782                 wake_up_interruptible_sync(&pipe->wait);
1783                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
1784                 pipe_wait(pipe);
1785         }
1786
1787         pipe->readers--;
1788         pipe->writers++;
1789         pipe_unlock(pipe);
1790
1791 }
1792
1793
1794 void do_coredump(long signr, int exit_code, struct pt_regs *regs)
1795 {
1796         struct core_state core_state;
1797         char corename[CORENAME_MAX_SIZE + 1];
1798         struct mm_struct *mm = current->mm;
1799         struct linux_binfmt * binfmt;
1800         struct inode * inode;
1801         const struct cred *old_cred;
1802         struct cred *cred;
1803         int retval = 0;
1804         int flag = 0;
1805         int ispipe = 0;
1806         char **helper_argv = NULL;
1807         int helper_argc = 0;
1808         int dump_count = 0;
1809         static atomic_t core_dump_count = ATOMIC_INIT(0);
1810         struct coredump_params cprm = {
1811                 .signr = signr,
1812                 .regs = regs,
1813                 .limit = rlimit(RLIMIT_CORE),
1814         };
1815
1816         audit_core_dumps(signr);
1817
1818         binfmt = mm->binfmt;
1819         if (!binfmt || !binfmt->core_dump)
1820                 goto fail;
1821
1822         cred = prepare_creds();
1823         if (!cred) {
1824                 retval = -ENOMEM;
1825                 goto fail;
1826         }
1827
1828         down_write(&mm->mmap_sem);
1829         /*
1830          * If another thread got here first, or we are not dumpable, bail out.
1831          */
1832         if (mm->core_state || !get_dumpable(mm)) {
1833                 up_write(&mm->mmap_sem);
1834                 put_cred(cred);
1835                 goto fail;
1836         }
1837
1838         /*
1839          *      We cannot trust fsuid as being the "true" uid of the
1840          *      process nor do we know its entire history. We only know it
1841          *      was tainted so we dump it as root in mode 2.
1842          */
1843         if (get_dumpable(mm) == 2) {    /* Setuid core dump mode */
1844                 flag = O_EXCL;          /* Stop rewrite attacks */
1845                 cred->fsuid = 0;        /* Dump root private */
1846         }
1847
1848         retval = coredump_wait(exit_code, &core_state);
1849         if (retval < 0) {
1850                 put_cred(cred);
1851                 goto fail;
1852         }
1853
1854         old_cred = override_creds(cred);
1855
1856         /*
1857          * Clear any false indication of pending signals that might
1858          * be seen by the filesystem code called to write the core file.
1859          */
1860         clear_thread_flag(TIF_SIGPENDING);
1861
1862         /*
1863          * lock_kernel() because format_corename() is controlled by sysctl, which
1864          * uses lock_kernel()
1865          */
1866         lock_kernel();
1867         ispipe = format_corename(corename, signr);
1868         unlock_kernel();
1869
1870         if ((!ispipe) && (cprm.limit < binfmt->min_coredump))
1871                 goto fail_unlock;
1872
1873         if (ispipe) {
1874                 if (cprm.limit == 0) {
1875                         /*
1876                          * Normally core limits are irrelevant to pipes, since
1877                          * we're not writing to the file system, but we use
1878                          * cprm.limit of 0 here as a speacial value. Any
1879                          * non-zero limit gets set to RLIM_INFINITY below, but
1880                          * a limit of 0 skips the dump.  This is a consistent
1881                          * way to catch recursive crashes.  We can still crash
1882                          * if the core_pattern binary sets RLIM_CORE =  !0
1883                          * but it runs as root, and can do lots of stupid things
1884                          * Note that we use task_tgid_vnr here to grab the pid
1885                          * of the process group leader.  That way we get the
1886                          * right pid if a thread in a multi-threaded
1887                          * core_pattern process dies.
1888                          */
1889                         printk(KERN_WARNING
1890                                 "Process %d(%s) has RLIMIT_CORE set to 0\n",
1891                                 task_tgid_vnr(current), current->comm);
1892                         printk(KERN_WARNING "Aborting core\n");
1893                         goto fail_unlock;
1894                 }
1895
1896                 dump_count = atomic_inc_return(&core_dump_count);
1897                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
1898                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
1899                                task_tgid_vnr(current), current->comm);
1900                         printk(KERN_WARNING "Skipping core dump\n");
1901                         goto fail_dropcount;
1902                 }
1903
1904                 helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc);
1905                 if (!helper_argv) {
1906                         printk(KERN_WARNING "%s failed to allocate memory\n",
1907                                __func__);
1908                         goto fail_dropcount;
1909                 }
1910
1911                 cprm.limit = RLIM_INFINITY;
1912
1913                 /* SIGPIPE can happen, but it's just never processed */
1914                 if (call_usermodehelper_pipe(helper_argv[0], helper_argv, NULL,
1915                                 &cprm.file)) {
1916                         printk(KERN_INFO "Core dump to %s pipe failed\n",
1917                                corename);
1918                         goto fail_dropcount;
1919                 }
1920         } else
1921                 cprm.file = filp_open(corename,
1922                                  O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
1923                                  0600);
1924         if (IS_ERR(cprm.file))
1925                 goto fail_dropcount;
1926         inode = cprm.file->f_path.dentry->d_inode;
1927         if (inode->i_nlink > 1)
1928                 goto close_fail;        /* multiple links - don't dump */
1929         if (!ispipe && d_unhashed(cprm.file->f_path.dentry))
1930                 goto close_fail;
1931
1932         /* AK: actually i see no reason to not allow this for named pipes etc.,
1933            but keep the previous behaviour for now. */
1934         if (!ispipe && !S_ISREG(inode->i_mode))
1935                 goto close_fail;
1936         /*
1937          * Dont allow local users get cute and trick others to coredump
1938          * into their pre-created files:
1939          */
1940         if (inode->i_uid != current_fsuid())
1941                 goto close_fail;
1942         if (!cprm.file->f_op)
1943                 goto close_fail;
1944         if (!cprm.file->f_op->write)
1945                 goto close_fail;
1946         if (!ispipe &&
1947             do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file) != 0)
1948                 goto close_fail;
1949
1950         retval = binfmt->core_dump(&cprm);
1951
1952         if (retval)
1953                 current->signal->group_exit_code |= 0x80;
1954 close_fail:
1955         if (ispipe && core_pipe_limit)
1956                 wait_for_dump_helpers(cprm.file);
1957         filp_close(cprm.file, NULL);
1958 fail_dropcount:
1959         if (dump_count)
1960                 atomic_dec(&core_dump_count);
1961 fail_unlock:
1962         if (helper_argv)
1963                 argv_free(helper_argv);
1964
1965         revert_creds(old_cred);
1966         put_cred(cred);
1967         coredump_finish(mm);
1968 fail:
1969         return;
1970 }