fs/coredump.c

   1 #include <linux/slab.h>
   2 #include <linux/file.h>
   3 #include <linux/fdtable.h>
   4 #include <linux/mm.h>
   5 #include <linux/stat.h>
   6 #include <linux/fcntl.h>
   7 #include <linux/swap.h>
   8 #include <linux/string.h>
   9 #include <linux/init.h>
  10 #include <linux/pagemap.h>
  11 #include <linux/perf_event.h>
  12 #include <linux/highmem.h>
  13 #include <linux/spinlock.h>
  14 #include <linux/key.h>
  15 #include <linux/personality.h>
  16 #include <linux/binfmts.h>
  17 #include <linux/coredump.h>
  18 #include <linux/utsname.h>
  19 #include <linux/pid_namespace.h>
  20 #include <linux/module.h>
  21 #include <linux/namei.h>
  22 #include <linux/mount.h>
  23 #include <linux/security.h>
  24 #include <linux/syscalls.h>
  25 #include <linux/tsacct_kern.h>
  26 #include <linux/cn_proc.h>
  27 #include <linux/audit.h>
  28 #include <linux/tracehook.h>
  29 #include <linux/kmod.h>
  30 #include <linux/fsnotify.h>
  31 #include <linux/fs_struct.h>
  32 #include <linux/pipe_fs_i.h>
  33 #include <linux/oom.h>
  34 #include <linux/compat.h>
  35 #include <linux/timekeeping.h>
  36
  37 #include <asm/uaccess.h>
  38 #include <asm/mmu_context.h>
  39 #include <asm/tlb.h>
  40 #include <asm/exec.h>
  41
  42 #include <trace/events/task.h>
  43 #include "internal.h"
  44
  45 #include <trace/events/sched.h>
  46
  47 int core_uses_pid;
  48 unsigned int core_pipe_limit;
  49 char core_pattern[CORENAME_MAX_SIZE] = "core";
  50 static int core_name_size = CORENAME_MAX_SIZE;
  51
  52 struct core_name {
  53         char *corename;
  54         int used, size;
  55 };
  56
  57 /* The maximal length of core_pattern is also specified in sysctl.c */
  58
  59 static int expand_corename(struct core_name *cn, int size)
  60 {
  61         char *corename = krealloc(cn->corename, size, GFP_KERNEL);
  62
  63         if (!corename)
  64                 return -ENOMEM;
  65
  66         if (size > core_name_size) /* racy but harmless */
  67                 core_name_size = size;
  68
  69         cn->size = ksize(corename);
  70         cn->corename = corename;
  71         return 0;
  72 }
  73
  74 static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
  75                                      va_list arg)
  76 {
  77         int free, need;
  78         va_list arg_copy;
  79
  80 again:
  81         free = cn->size - cn->used;
  82
  83         va_copy(arg_copy, arg);
  84         need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
  85         va_end(arg_copy);
  86
  87         if (need < free) {
  88                 cn->used += need;
  89                 return 0;
  90         }
  91
  92         if (!expand_corename(cn, cn->size + need - free + 1))
  93                 goto again;
  94
  95         return -ENOMEM;
  96 }
  97
  98 static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
  99 {
 100         va_list arg;
 101         int ret;
 102
 103         va_start(arg, fmt);
 104         ret = cn_vprintf(cn, fmt, arg);
 105         va_end(arg);
 106
 107         return ret;
 108 }
 109
 110 static __printf(2, 3)
 111 int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
 112 {
 113         int cur = cn->used;
 114         va_list arg;
 115         int ret;
 116
 117         va_start(arg, fmt);
 118         ret = cn_vprintf(cn, fmt, arg);
 119         va_end(arg);
 120
 121         for (; cur < cn->used; ++cur) {
 122                 if (cn->corename[cur] == '/')
 123                         cn->corename[cur] = '!';
 124         }
 125         return ret;
 126 }
 127
 128 static int cn_print_exe_file(struct core_name *cn)
 129 {
 130         struct file *exe_file;
 131         char *pathbuf, *path;
 132         int ret;
 133
 134         exe_file = get_mm_exe_file(current->mm);
 135         if (!exe_file)
 136                 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
 137
 138         pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY);
 139         if (!pathbuf) {
 140                 ret = -ENOMEM;
 141                 goto put_exe_file;
 142         }
 143
 144         path = file_path(exe_file, pathbuf, PATH_MAX);
 145         if (IS_ERR(path)) {
 146                 ret = PTR_ERR(path);
 147                 goto free_buf;
 148         }
 149
 150         ret = cn_esc_printf(cn, "%s", path);
 151
 152 free_buf:
 153         kfree(pathbuf);
 154 put_exe_file:
 155         fput(exe_file);
 156         return ret;
 157 }
 158
 159 /* format_corename will inspect the pattern parameter, and output a
 160  * name into corename, which must have space for at least
 161  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
 162  */
 163 static int format_corename(struct core_name *cn, struct coredump_params *cprm)
 164 {
 165         const struct cred *cred = current_cred();
 166         const char *pat_ptr = core_pattern;
 167         int ispipe = (*pat_ptr == '|');
 168         int pid_in_pattern = 0;
 169         int err = 0;
 170
 171         cn->used = 0;
 172         cn->corename = NULL;
 173         if (expand_corename(cn, core_name_size))
 174                 return -ENOMEM;
 175         cn->corename[0] = '\0';
 176
 177         if (ispipe)
 178                 ++pat_ptr;
 179
 180         /* Repeat as long as we have more pattern to process and more output
 181            space */
 182         while (*pat_ptr) {
 183                 if (*pat_ptr != '%') {
 184                         err = cn_printf(cn, "%c", *pat_ptr++);
 185                 } else {
 186                         switch (*++pat_ptr) {
 187                         /* single % at the end, drop that */
 188                         case 0:
 189                                 goto out;
 190                         /* Double percent, output one percent */
 191                         case '%':
 192                                 err = cn_printf(cn, "%c", '%');
 193                                 break;
 194                         /* pid */
 195                         case 'p':
 196                                 pid_in_pattern = 1;
 197                                 err = cn_printf(cn, "%d",
 198                                               task_tgid_vnr(current));
 199                                 break;
 200                         /* global pid */
 201                         case 'P':
 202                                 err = cn_printf(cn, "%d",
 203                                               task_tgid_nr(current));
 204                                 break;
 205                         case 'i':
 206                                 err = cn_printf(cn, "%d",
 207                                               task_pid_vnr(current));
 208                                 break;
 209                         case 'I':
 210                                 err = cn_printf(cn, "%d",
 211                                               task_pid_nr(current));
 212                                 break;
 213                         /* uid */
 214                         case 'u':
 215                                 err = cn_printf(cn, "%u",
 216                                                 from_kuid(&init_user_ns,
 217                                                           cred->uid));
 218                                 break;
 219                         /* gid */
 220                         case 'g':
 221                                 err = cn_printf(cn, "%u",
 222                                                 from_kgid(&init_user_ns,
 223                                                           cred->gid));
 224                                 break;
 225                         case 'd':
 226                                 err = cn_printf(cn, "%d",
 227                                         __get_dumpable(cprm->mm_flags));
 228                                 break;
 229                         /* signal that caused the coredump */
 230                         case 's':
 231                                 err = cn_printf(cn, "%d",
 232                                                 cprm->siginfo->si_signo);
 233                                 break;
 234                         /* UNIX time of coredump */
 235                         case 't': {
 236                                 time64_t time;
 237
 238                                 time = ktime_get_real_seconds();
 239                                 err = cn_printf(cn, "%lld", time);
 240                                 break;
 241                         }
 242                         /* hostname */
 243                         case 'h':
 244                                 down_read(&uts_sem);
 245                                 err = cn_esc_printf(cn, "%s",
 246                                               utsname()->nodename);
 247                                 up_read(&uts_sem);
 248                                 break;
 249                         /* executable */
 250                         case 'e':
 251                                 err = cn_esc_printf(cn, "%s", current->comm);
 252                                 break;
 253                         case 'E':
 254                                 err = cn_print_exe_file(cn);
 255                                 break;
 256                         /* core limit size */
 257                         case 'c':
 258                                 err = cn_printf(cn, "%lu",
 259                                               rlimit(RLIMIT_CORE));
 260                                 break;
 261                         default:
 262                                 break;
 263                         }
 264                         ++pat_ptr;
 265                 }
 266
 267                 if (err)
 268                         return err;
 269         }
 270
 271 out:
 272         /* Backward compatibility with core_uses_pid:
 273          *
 274          * If core_pattern does not include a %p (as is the default)
 275          * and core_uses_pid is set, then .%pid will be appended to
 276          * the filename. Do not do this for piped commands. */
 277         if (!ispipe && !pid_in_pattern && core_uses_pid) {
 278                 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
 279                 if (err)
 280                         return err;
 281         }
 282         return ispipe;
 283 }
 284
 285 static int zap_process(struct task_struct *start, int exit_code, int flags)
 286 {
 287         struct task_struct *t;
 288         int nr = 0;
 289
 290         /* ignore all signals except SIGKILL, see prepare_signal() */
 291         start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
 292         start->signal->group_exit_code = exit_code;
 293         start->signal->group_stop_count = 0;
 294
 295         for_each_thread(start, t) {
 296                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
 297                 if (t != current && t->mm) {
 298                         sigaddset(&t->pending.signal, SIGKILL);
 299                         signal_wake_up(t, 1);
 300                         nr++;
 301                 }
 302         }
 303
 304         return nr;
 305 }
 306
 307 static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
 308                         struct core_state *core_state, int exit_code)
 309 {
 310         struct task_struct *g, *p;
 311         unsigned long flags;
 312         int nr = -EAGAIN;
 313
 314         spin_lock_irq(&tsk->sighand->siglock);
 315         if (!signal_group_exit(tsk->signal)) {
 316                 mm->core_state = core_state;
 317                 tsk->signal->group_exit_task = tsk;
 318                 nr = zap_process(tsk, exit_code, 0);
 319                 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
 320         }
 321         spin_unlock_irq(&tsk->sighand->siglock);
 322         if (unlikely(nr < 0))
 323                 return nr;
 324
 325         tsk->flags |= PF_DUMPCORE;
 326         if (atomic_read(&mm->mm_users) == nr + 1)
 327                 goto done;
 328         /*
 329          * We should find and kill all tasks which use this mm, and we should
 330          * count them correctly into ->nr_threads. We don't take tasklist
 331          * lock, but this is safe wrt:
 332          *
 333          * fork:
 334          *      None of sub-threads can fork after zap_process(leader). All
 335          *      processes which were created before this point should be
 336          *      visible to zap_threads() because copy_process() adds the new
 337          *      process to the tail of init_task.tasks list, and lock/unlock
 338          *      of ->siglock provides a memory barrier.
 339          *
 340          * do_exit:
 341          *      The caller holds mm->mmap_sem. This means that the task which
 342          *      uses this mm can't pass exit_mm(), so it can't exit or clear
 343          *      its ->mm.
 344          *
 345          * de_thread:
 346          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
 347          *      we must see either old or new leader, this does not matter.
 348          *      However, it can change p->sighand, so lock_task_sighand(p)
 349          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
 350          *      it can't fail.
 351          *
 352          *      Note also that "g" can be the old leader with ->mm == NULL
 353          *      and already unhashed and thus removed from ->thread_group.
 354          *      This is OK, __unhash_process()->list_del_rcu() does not
 355          *      clear the ->next pointer, we will find the new leader via
 356          *      next_thread().
 357          */
 358         rcu_read_lock();
 359         for_each_process(g) {
 360                 if (g == tsk->group_leader)
 361                         continue;
 362                 if (g->flags & PF_KTHREAD)
 363                         continue;
 364
 365                 for_each_thread(g, p) {
 366                         if (unlikely(!p->mm))
 367                                 continue;
 368                         if (unlikely(p->mm == mm)) {
 369                                 lock_task_sighand(p, &flags);
 370                                 nr += zap_process(p, exit_code,
 371                                                         SIGNAL_GROUP_EXIT);
 372                                 unlock_task_sighand(p, &flags);
 373                         }
 374                         break;
 375                 }
 376         }
 377         rcu_read_unlock();
 378 done:
 379         atomic_set(&core_state->nr_threads, nr);
 380         return nr;
 381 }
 382
 383 static int coredump_wait(int exit_code, struct core_state *core_state)
 384 {
 385         struct task_struct *tsk = current;
 386         struct mm_struct *mm = tsk->mm;
 387         int core_waiters = -EBUSY;
 388
 389         init_completion(&core_state->startup);
 390         core_state->dumper.task = tsk;
 391         core_state->dumper.next = NULL;
 392
 393         down_write(&mm->mmap_sem);
 394         if (!mm->core_state)
 395                 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
 396         up_write(&mm->mmap_sem);
 397
 398         if (core_waiters > 0) {
 399                 struct core_thread *ptr;
 400
 401                 wait_for_completion(&core_state->startup);
 402                 /*
 403                  * Wait for all the threads to become inactive, so that
 404                  * all the thread context (extended register state, like
 405                  * fpu etc) gets copied to the memory.
 406                  */
 407                 ptr = core_state->dumper.next;
 408                 while (ptr != NULL) {
 409                         wait_task_inactive(ptr->task, 0);
 410                         ptr = ptr->next;
 411                 }
 412         }
 413
 414         return core_waiters;
 415 }
 416
 417 static void coredump_finish(struct mm_struct *mm, bool core_dumped)
 418 {
 419         struct core_thread *curr, *next;
 420         struct task_struct *task;
 421
 422         spin_lock_irq(&current->sighand->siglock);
 423         if (core_dumped && !__fatal_signal_pending(current))
 424                 current->signal->group_exit_code |= 0x80;
 425         current->signal->group_exit_task = NULL;
 426         current->signal->flags = SIGNAL_GROUP_EXIT;
 427         spin_unlock_irq(&current->sighand->siglock);
 428
 429         next = mm->core_state->dumper.next;
 430         while ((curr = next) != NULL) {
 431                 next = curr->next;
 432                 task = curr->task;
 433                 /*
 434                  * see exit_mm(), curr->task must not see
 435                  * ->task == NULL before we read ->next.
 436                  */
 437                 smp_mb();
 438                 curr->task = NULL;
 439                 wake_up_process(task);
 440         }
 441
 442         mm->core_state = NULL;
 443 }
 444
 445 static bool dump_interrupted(void)
 446 {
 447         /*
 448          * SIGKILL or freezing() interrupt the coredumping. Perhaps we
 449          * can do try_to_freeze() and check __fatal_signal_pending(),
 450          * but then we need to teach dump_write() to restart and clear
 451          * TIF_SIGPENDING.
 452          */
 453         return signal_pending(current);
 454 }
 455
 456 static void wait_for_dump_helpers(struct file *file)
 457 {
 458         struct pipe_inode_info *pipe = file->private_data;
 459
 460         pipe_lock(pipe);
 461         pipe->readers++;
 462         pipe->writers--;
 463         wake_up_interruptible_sync(&pipe->wait);
 464         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 465         pipe_unlock(pipe);
 466
 467         /*
 468          * We actually want wait_event_freezable() but then we need
 469          * to clear TIF_SIGPENDING and improve dump_interrupted().
 470          */
 471         wait_event_interruptible(pipe->wait, pipe->readers == 1);
 472
 473         pipe_lock(pipe);
 474         pipe->readers--;
 475         pipe->writers++;
 476         pipe_unlock(pipe);
 477 }
 478
 479 /*
 480  * umh_pipe_setup
 481  * helper function to customize the process used
 482  * to collect the core in userspace.  Specifically
 483  * it sets up a pipe and installs it as fd 0 (stdin)
 484  * for the process.  Returns 0 on success, or
 485  * PTR_ERR on failure.
 486  * Note that it also sets the core limit to 1.  This
 487  * is a special value that we use to trap recursive
 488  * core dumps
 489  */
 490 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
 491 {
 492         struct file *files[2];
 493         struct coredump_params *cp = (struct coredump_params *)info->data;
 494         int err = create_pipe_files(files, 0);
 495         if (err)
 496                 return err;
 497
 498         cp->file = files[1];
 499
 500         err = replace_fd(0, files[0], 0);
 501         fput(files[0]);
 502         /* and disallow core files too */
 503         current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
 504
 505         return err;
 506 }
 507
 508 void do_coredump(const siginfo_t *siginfo)
 509 {
 510         struct core_state core_state;
 511         struct core_name cn;
 512         struct mm_struct *mm = current->mm;
 513         struct linux_binfmt * binfmt;
 514         const struct cred *old_cred;
 515         struct cred *cred;
 516         int retval = 0;
 517         int ispipe;
 518         struct files_struct *displaced;
 519         /* require nonrelative corefile path and be extra careful */
 520         bool need_suid_safe = false;
 521         bool core_dumped = false;
 522         static atomic_t core_dump_count = ATOMIC_INIT(0);
 523         struct coredump_params cprm = {
 524                 .siginfo = siginfo,
 525                 .regs = signal_pt_regs(),
 526                 .limit = rlimit(RLIMIT_CORE),
 527                 /*
 528                  * We must use the same mm->flags while dumping core to avoid
 529                  * inconsistency of bit flags, since this flag is not protected
 530                  * by any locks.
 531                  */
 532                 .mm_flags = mm->flags,
 533         };
 534
 535         audit_core_dumps(siginfo->si_signo);
 536
 537         binfmt = mm->binfmt;
 538         if (!binfmt || !binfmt->core_dump)
 539                 goto fail;
 540         if (!__get_dumpable(cprm.mm_flags))
 541                 goto fail;
 542
 543         cred = prepare_creds();
 544         if (!cred)
 545                 goto fail;
 546         /*
 547          * We cannot trust fsuid as being the "true" uid of the process
 548          * nor do we know its entire history. We only know it was tainted
 549          * so we dump it as root in mode 2, and only into a controlled
 550          * environment (pipe handler or fully qualified path).
 551          */
 552         if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
 553                 /* Setuid core dump mode */
 554                 cred->fsuid = GLOBAL_ROOT_UID;  /* Dump root private */
 555                 need_suid_safe = true;
 556         }
 557
 558         retval = coredump_wait(siginfo->si_signo, &core_state);
 559         if (retval < 0)
 560                 goto fail_creds;
 561
 562         old_cred = override_creds(cred);
 563
 564         ispipe = format_corename(&cn, &cprm);
 565
 566         if (ispipe) {
 567                 int dump_count;
 568                 char **helper_argv;
 569                 struct subprocess_info *sub_info;
 570
 571                 if (ispipe < 0) {
 572                         printk(KERN_WARNING "format_corename failed\n");
 573                         printk(KERN_WARNING "Aborting core\n");
 574                         goto fail_unlock;
 575                 }
 576
 577                 if (cprm.limit == 1) {
 578                         /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
 579                          *
 580                          * Normally core limits are irrelevant to pipes, since
 581                          * we're not writing to the file system, but we use
 582                          * cprm.limit of 1 here as a special value, this is a
 583                          * consistent way to catch recursive crashes.
 584                          * We can still crash if the core_pattern binary sets
 585                          * RLIM_CORE = !1, but it runs as root, and can do
 586                          * lots of stupid things.
 587                          *
 588                          * Note that we use task_tgid_vnr here to grab the pid
 589                          * of the process group leader.  That way we get the
 590                          * right pid if a thread in a multi-threaded
 591                          * core_pattern process dies.
 592                          */
 593                         printk(KERN_WARNING
 594                                 "Process %d(%s) has RLIMIT_CORE set to 1\n",
 595                                 task_tgid_vnr(current), current->comm);
 596                         printk(KERN_WARNING "Aborting core\n");
 597                         goto fail_unlock;
 598                 }
 599                 cprm.limit = RLIM_INFINITY;
 600
 601                 dump_count = atomic_inc_return(&core_dump_count);
 602                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
 603                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
 604                                task_tgid_vnr(current), current->comm);
 605                         printk(KERN_WARNING "Skipping core dump\n");
 606                         goto fail_dropcount;
 607                 }
 608
 609                 helper_argv = argv_split(GFP_KERNEL, cn.corename, NULL);
 610                 if (!helper_argv) {
 611                         printk(KERN_WARNING "%s failed to allocate memory\n",
 612                                __func__);
 613                         goto fail_dropcount;
 614                 }
 615
 616                 retval = -ENOMEM;
 617                 sub_info = call_usermodehelper_setup(helper_argv[0],
 618                                                 helper_argv, NULL, GFP_KERNEL,
 619                                                 umh_pipe_setup, NULL, &cprm);
 620                 if (sub_info)
 621                         retval = call_usermodehelper_exec(sub_info,
 622                                                           UMH_WAIT_EXEC);
 623
 624                 argv_free(helper_argv);
 625                 if (retval) {
 626                         printk(KERN_INFO "Core dump to |%s pipe failed\n",
 627                                cn.corename);
 628                         goto close_fail;
 629                 }
 630         } else {
 631                 struct inode *inode;
 632
 633                 if (cprm.limit < binfmt->min_coredump)
 634                         goto fail_unlock;
 635
 636                 if (need_suid_safe && cn.corename[0] != '/') {
 637                         printk(KERN_WARNING "Pid %d(%s) can only dump core "\
 638                                 "to fully qualified path!\n",
 639                                 task_tgid_vnr(current), current->comm);
 640                         printk(KERN_WARNING "Skipping core dump\n");
 641                         goto fail_unlock;
 642                 }
 643
 644                 /*
 645                  * Unlink the file if it exists unless this is a SUID
 646                  * binary - in that case, we're running around with root
 647                  * privs and don't want to unlink another user's coredump.
 648                  */
 649                 if (!need_suid_safe) {
 650                         mm_segment_t old_fs;
 651
 652                         old_fs = get_fs();
 653                         set_fs(KERNEL_DS);
 654                         /*
 655                          * If it doesn't exist, that's fine. If there's some
 656                          * other problem, we'll catch it at the filp_open().
 657                          */
 658                         (void) sys_unlink((const char __user *)cn.corename);
 659                         set_fs(old_fs);
 660                 }
 661
 662                 /*
 663                  * There is a race between unlinking and creating the
 664                  * file, but if that causes an EEXIST here, that's
 665                  * fine - another process raced with us while creating
 666                  * the corefile, and the other process won. To userspace,
 667                  * what matters is that at least one of the two processes
 668                  * writes its coredump successfully, not which one.
 669                  */
 670                 cprm.file = filp_open(cn.corename,
 671                                  O_CREAT | 2 | O_NOFOLLOW |
 672                                  O_LARGEFILE | O_EXCL,
 673                                  0600);
 674                 if (IS_ERR(cprm.file))
 675                         goto fail_unlock;
 676
 677                 inode = file_inode(cprm.file);
 678                 if (inode->i_nlink > 1)
 679                         goto close_fail;
 680                 if (d_unhashed(cprm.file->f_path.dentry))
 681                         goto close_fail;
 682                 /*
 683                  * AK: actually i see no reason to not allow this for named
 684                  * pipes etc, but keep the previous behaviour for now.
 685                  */
 686                 if (!S_ISREG(inode->i_mode))
 687                         goto close_fail;
 688                 /*
 689                  * Don't dump core if the filesystem changed owner or mode
 690                  * of the file during file creation. This is an issue when
 691                  * a process dumps core while its cwd is e.g. on a vfat
 692                  * filesystem.
 693                  */
 694                 if (!uid_eq(inode->i_uid, current_fsuid()))
 695                         goto close_fail;
 696                 if ((inode->i_mode & 0677) != 0600)
 697                         goto close_fail;
 698                 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
 699                         goto close_fail;
 700                 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
 701                         goto close_fail;
 702         }
 703
 704         /* get us an unshared descriptor table; almost always a no-op */
 705         retval = unshare_files(&displaced);
 706         if (retval)
 707                 goto close_fail;
 708         if (displaced)
 709                 put_files_struct(displaced);
 710         if (!dump_interrupted()) {
 711                 file_start_write(cprm.file);
 712                 core_dumped = binfmt->core_dump(&cprm);
 713                 file_end_write(cprm.file);
 714         }
 715         if (ispipe && core_pipe_limit)
 716                 wait_for_dump_helpers(cprm.file);
 717 close_fail:
 718         if (cprm.file)
 719                 filp_close(cprm.file, NULL);
 720 fail_dropcount:
 721         if (ispipe)
 722                 atomic_dec(&core_dump_count);
 723 fail_unlock:
 724         kfree(cn.corename);
 725         coredump_finish(mm, core_dumped);
 726         revert_creds(old_cred);
 727 fail_creds:
 728         put_cred(cred);
 729 fail:
 730         return;
 731 }
 732
 733 /*
 734  * Core dumping helper functions.  These are the only things you should
 735  * do on a core-file: use only these functions to write out all the
 736  * necessary info.
 737  */
 738 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
 739 {
 740         struct file *file = cprm->file;
 741         loff_t pos = file->f_pos;
 742         ssize_t n;
 743         if (cprm->written + nr > cprm->limit)
 744                 return 0;
 745         while (nr) {
 746                 if (dump_interrupted())
 747                         return 0;
 748                 n = __kernel_write(file, addr, nr, &pos);
 749                 if (n <= 0)
 750                         return 0;
 751                 file->f_pos = pos;
 752                 cprm->written += n;
 753                 nr -= n;
 754         }
 755         return 1;
 756 }
 757 EXPORT_SYMBOL(dump_emit);
 758
 759 int dump_skip(struct coredump_params *cprm, size_t nr)
 760 {
 761         static char zeroes[PAGE_SIZE];
 762         struct file *file = cprm->file;
 763         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
 764                 if (cprm->written + nr > cprm->limit)
 765                         return 0;
 766                 if (dump_interrupted() ||
 767                     file->f_op->llseek(file, nr, SEEK_CUR) < 0)
 768                         return 0;
 769                 cprm->written += nr;
 770                 return 1;
 771         } else {
 772                 while (nr > PAGE_SIZE) {
 773                         if (!dump_emit(cprm, zeroes, PAGE_SIZE))
 774                                 return 0;
 775                         nr -= PAGE_SIZE;
 776                 }
 777                 return dump_emit(cprm, zeroes, nr);
 778         }
 779 }
 780 EXPORT_SYMBOL(dump_skip);
 781
 782 int dump_align(struct coredump_params *cprm, int align)
 783 {
 784         unsigned mod = cprm->written & (align - 1);
 785         if (align & (align - 1))
 786                 return 0;
 787         return mod ? dump_skip(cprm, align - mod) : 1;
 788 }
 789 EXPORT_SYMBOL(dump_align);