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