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