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