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->flags = SIGNAL_GROUP_EXIT;
 267        start->signal->group_exit_code = exit_code;
 268        start->signal->group_stop_count = 0;
 269
 270        t = start;
 271        do {
 272                task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
 273                if (t != current && t->mm) {
 274                        sigaddset(&t->pending.signal, SIGKILL);
 275                        signal_wake_up(t, 1);
 276                        nr++;
 277                }
 278        } while_each_thread(start, t);
 279
 280        return nr;
 281}
 282
 283static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
 284                                struct core_state *core_state, int exit_code)
 285{
 286        struct task_struct *g, *p;
 287        unsigned long flags;
 288        int nr = -EAGAIN;
 289
 290        spin_lock_irq(&tsk->sighand->siglock);
 291        if (!signal_group_exit(tsk->signal)) {
 292                mm->core_state = core_state;
 293                nr = zap_process(tsk, exit_code);
 294        }
 295        spin_unlock_irq(&tsk->sighand->siglock);
 296        if (unlikely(nr < 0))
 297                return nr;
 298
 299        if (atomic_read(&mm->mm_users) == nr + 1)
 300                goto done;
 301        /*
 302         * We should find and kill all tasks which use this mm, and we should
 303         * count them correctly into ->nr_threads. We don't take tasklist
 304         * lock, but this is safe wrt:
 305         *
 306         * fork:
 307         *      None of sub-threads can fork after zap_process(leader). All
 308         *      processes which were created before this point should be
 309         *      visible to zap_threads() because copy_process() adds the new
 310         *      process to the tail of init_task.tasks list, and lock/unlock
 311         *      of ->siglock provides a memory barrier.
 312         *
 313         * do_exit:
 314         *      The caller holds mm->mmap_sem. This means that the task which
 315         *      uses this mm can't pass exit_mm(), so it can't exit or clear
 316         *      its ->mm.
 317         *
 318         * de_thread:
 319         *      It does list_replace_rcu(&leader->tasks, &current->tasks),
 320         *      we must see either old or new leader, this does not matter.
 321         *      However, it can change p->sighand, so lock_task_sighand(p)
 322         *      must be used. Since p->mm != NULL and we hold ->mmap_sem
 323         *      it can't fail.
 324         *
 325         *      Note also that "g" can be the old leader with ->mm == NULL
 326         *      and already unhashed and thus removed from ->thread_group.
 327         *      This is OK, __unhash_process()->list_del_rcu() does not
 328         *      clear the ->next pointer, we will find the new leader via
 329         *      next_thread().
 330         */
 331        rcu_read_lock();
 332        for_each_process(g) {
 333                if (g == tsk->group_leader)
 334                        continue;
 335                if (g->flags & PF_KTHREAD)
 336                        continue;
 337                p = g;
 338                do {
 339                        if (p->mm) {
 340                                if (unlikely(p->mm == mm)) {
 341                                        lock_task_sighand(p, &flags);
 342                                        nr += zap_process(p, exit_code);
 343                                        unlock_task_sighand(p, &flags);
 344                                }
 345                                break;
 346                        }
 347                } while_each_thread(g, p);
 348        }
 349        rcu_read_unlock();
 350done:
 351        atomic_set(&core_state->nr_threads, nr);
 352        return nr;
 353}
 354
 355static int coredump_wait(int exit_code, struct core_state *core_state)
 356{
 357        struct task_struct *tsk = current;
 358        struct mm_struct *mm = tsk->mm;
 359        int core_waiters = -EBUSY;
 360
 361        init_completion(&core_state->startup);
 362        core_state->dumper.task = tsk;
 363        core_state->dumper.next = NULL;
 364
 365        down_write(&mm->mmap_sem);
 366        if (!mm->core_state)
 367                core_waiters = zap_threads(tsk, mm, core_state, exit_code);
 368        up_write(&mm->mmap_sem);
 369
 370        if (core_waiters > 0) {
 371                struct core_thread *ptr;
 372
 373                wait_for_completion(&core_state->startup);
 374                /*
 375                 * Wait for all the threads to become inactive, so that
 376                 * all the thread context (extended register state, like
 377                 * fpu etc) gets copied to the memory.
 378                 */
 379                ptr = core_state->dumper.next;
 380                while (ptr != NULL) {
 381                        wait_task_inactive(ptr->task, 0);
 382                        ptr = ptr->next;
 383                }
 384        }
 385
 386        return core_waiters;
 387}
 388
 389static void coredump_finish(struct mm_struct *mm)
 390{
 391        struct core_thread *curr, *next;
 392        struct task_struct *task;
 393
 394        next = mm->core_state->dumper.next;
 395        while ((curr = next) != NULL) {
 396                next = curr->next;
 397                task = curr->task;
 398                /*
 399                 * see exit_mm(), curr->task must not see
 400                 * ->task == NULL before we read ->next.
 401                 */
 402                smp_mb();
 403                curr->task = NULL;
 404                wake_up_process(task);
 405        }
 406
 407        mm->core_state = NULL;
 408}
 409
 410static void wait_for_dump_helpers(struct file *file)
 411{
 412        struct pipe_inode_info *pipe;
 413
 414        pipe = file_inode(file)->i_pipe;
 415
 416        pipe_lock(pipe);
 417        pipe->readers++;
 418        pipe->writers--;
 419
 420        while ((pipe->readers > 1) && (!signal_pending(current))) {
 421                wake_up_interruptible_sync(&pipe->wait);
 422                kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 423                pipe_wait(pipe);
 424        }
 425
 426        pipe->readers--;
 427        pipe->writers++;
 428        pipe_unlock(pipe);
 429
 430}
 431
 432/*
 433 * umh_pipe_setup
 434 * helper function to customize the process used
 435 * to collect the core in userspace.  Specifically
 436 * it sets up a pipe and installs it as fd 0 (stdin)
 437 * for the process.  Returns 0 on success, or
 438 * PTR_ERR on failure.
 439 * Note that it also sets the core limit to 1.  This
 440 * is a special value that we use to trap recursive
 441 * core dumps
 442 */
 443static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
 444{
 445        struct file *files[2];
 446        struct coredump_params *cp = (struct coredump_params *)info->data;
 447        int err = create_pipe_files(files, 0);
 448        if (err)
 449                return err;
 450
 451        cp->file = files[1];
 452
 453        err = replace_fd(0, files[0], 0);
 454        fput(files[0]);
 455        /* and disallow core files too */
 456        current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
 457
 458        return err;
 459}
 460
 461void do_coredump(siginfo_t *siginfo)
 462{
 463        struct core_state core_state;
 464        struct core_name cn;
 465        struct mm_struct *mm = current->mm;
 466        struct linux_binfmt * binfmt;
 467        const struct cred *old_cred;
 468        struct cred *cred;
 469        int retval = 0;
 470        int flag = 0;
 471        int ispipe;
 472        struct files_struct *displaced;
 473        bool need_nonrelative = false;
 474        static atomic_t core_dump_count = ATOMIC_INIT(0);
 475        struct coredump_params cprm = {
 476                .siginfo = siginfo,
 477                .regs = signal_pt_regs(),
 478                .limit = rlimit(RLIMIT_CORE),
 479                /*
 480                 * We must use the same mm->flags while dumping core to avoid
 481                 * inconsistency of bit flags, since this flag is not protected
 482                 * by any locks.
 483                 */
 484                .mm_flags = mm->flags,
 485        };
 486
 487        audit_core_dumps(siginfo->si_signo);
 488
 489        binfmt = mm->binfmt;
 490        if (!binfmt || !binfmt->core_dump)
 491                goto fail;
 492        if (!__get_dumpable(cprm.mm_flags))
 493                goto fail;
 494
 495        cred = prepare_creds();
 496        if (!cred)
 497                goto fail;
 498        /*
 499         * We cannot trust fsuid as being the "true" uid of the process
 500         * nor do we know its entire history. We only know it was tainted
 501         * so we dump it as root in mode 2, and only into a controlled
 502         * environment (pipe handler or fully qualified path).
 503         */
 504        if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
 505                /* Setuid core dump mode */
 506                flag = O_EXCL;          /* Stop rewrite attacks */
 507                cred->fsuid = GLOBAL_ROOT_UID;  /* Dump root private */
 508                need_nonrelative = true;
 509        }
 510
 511        retval = coredump_wait(siginfo->si_signo, &core_state);
 512        if (retval < 0)
 513                goto fail_creds;
 514
 515        old_cred = override_creds(cred);
 516
 517        /*
 518         * Clear any false indication of pending signals that might
 519         * be seen by the filesystem code called to write the core file.
 520         */
 521        clear_thread_flag(TIF_SIGPENDING);
 522
 523        ispipe = format_corename(&cn, &cprm);
 524
 525        if (ispipe) {
 526                int dump_count;
 527                char **helper_argv;
 528
 529                if (ispipe < 0) {
 530                        printk(KERN_WARNING "format_corename failed\n");
 531                        printk(KERN_WARNING "Aborting core\n");
 532                        goto fail_corename;
 533                }
 534
 535                if (cprm.limit == 1) {
 536                        /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
 537                         *
 538                         * Normally core limits are irrelevant to pipes, since
 539                         * we're not writing to the file system, but we use
 540                         * cprm.limit of 1 here as a speacial value, this is a
 541                         * consistent way to catch recursive crashes.
 542                         * We can still crash if the core_pattern binary sets
 543                         * RLIM_CORE = !1, but it runs as root, and can do
 544                         * lots of stupid things.
 545                         *
 546                         * Note that we use task_tgid_vnr here to grab the pid
 547                         * of the process group leader.  That way we get the
 548                         * right pid if a thread in a multi-threaded
 549                         * core_pattern process dies.
 550                         */
 551                        printk(KERN_WARNING
 552                                "Process %d(%s) has RLIMIT_CORE set to 1\n",
 553                                task_tgid_vnr(current), current->comm);
 554                        printk(KERN_WARNING "Aborting core\n");
 555                        goto fail_unlock;
 556                }
 557                cprm.limit = RLIM_INFINITY;
 558
 559                dump_count = atomic_inc_return(&core_dump_count);
 560                if (core_pipe_limit && (core_pipe_limit < dump_count)) {
 561                        printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
 562                               task_tgid_vnr(current), current->comm);
 563                        printk(KERN_WARNING "Skipping core dump\n");
 564                        goto fail_dropcount;
 565                }
 566
 567                helper_argv = argv_split(GFP_KERNEL, cn.corename+1, NULL);
 568                if (!helper_argv) {
 569                        printk(KERN_WARNING "%s failed to allocate memory\n",
 570                               __func__);
 571                        goto fail_dropcount;
 572                }
 573
 574                retval = call_usermodehelper_fns(helper_argv[0], helper_argv,
 575                                        NULL, UMH_WAIT_EXEC, umh_pipe_setup,
 576                                        NULL, &cprm);
 577                argv_free(helper_argv);
 578                if (retval) {
 579                        printk(KERN_INFO "Core dump to %s pipe failed\n",
 580                               cn.corename);
 581                        goto close_fail;
 582                }
 583        } else {
 584                struct inode *inode;
 585
 586                if (cprm.limit < binfmt->min_coredump)
 587                        goto fail_unlock;
 588
 589                if (need_nonrelative && cn.corename[0] != '/') {
 590                        printk(KERN_WARNING "Pid %d(%s) can only dump core "\
 591                                "to fully qualified path!\n",
 592                                task_tgid_vnr(current), current->comm);
 593                        printk(KERN_WARNING "Skipping core dump\n");
 594                        goto fail_unlock;
 595                }
 596
 597                cprm.file = filp_open(cn.corename,
 598                                 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
 599                                 0600);
 600                if (IS_ERR(cprm.file))
 601                        goto fail_unlock;
 602
 603                inode = file_inode(cprm.file);
 604                if (inode->i_nlink > 1)
 605                        goto close_fail;
 606                if (d_unhashed(cprm.file->f_path.dentry))
 607                        goto close_fail;
 608                /*
 609                 * AK: actually i see no reason to not allow this for named
 610                 * pipes etc, but keep the previous behaviour for now.
 611                 */
 612                if (!S_ISREG(inode->i_mode))
 613                        goto close_fail;
 614                /*
 615                 * Dont allow local users get cute and trick others to coredump
 616                 * into their pre-created files.
 617                 */
 618                if (!uid_eq(inode->i_uid, current_fsuid()))
 619                        goto close_fail;
 620                if (!cprm.file->f_op || !cprm.file->f_op->write)
 621                        goto close_fail;
 622                if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
 623                        goto close_fail;
 624        }
 625
 626        /* get us an unshared descriptor table; almost always a no-op */
 627        retval = unshare_files(&displaced);
 628        if (retval)
 629                goto close_fail;
 630        if (displaced)
 631                put_files_struct(displaced);
 632        retval = binfmt->core_dump(&cprm);
 633        if (retval)
 634                current->signal->group_exit_code |= 0x80;
 635
 636        if (ispipe && core_pipe_limit)
 637                wait_for_dump_helpers(cprm.file);
 638close_fail:
 639        if (cprm.file)
 640                filp_close(cprm.file, NULL);
 641fail_dropcount:
 642        if (ispipe)
 643                atomic_dec(&core_dump_count);
 644fail_unlock:
 645        kfree(cn.corename);
 646fail_corename:
 647        coredump_finish(mm);
 648        revert_creds(old_cred);
 649fail_creds:
 650        put_cred(cred);
 651fail:
 652        return;
 653}
 654
 655/*
 656 * Core dumping helper functions.  These are the only things you should
 657 * do on a core-file: use only these functions to write out all the
 658 * necessary info.
 659 */
 660int dump_write(struct file *file, const void *addr, int nr)
 661{
 662        return access_ok(VERIFY_READ, addr, nr) && file->f_op->write(file, addr, nr, &file->f_pos) == nr;
 663}
 664EXPORT_SYMBOL(dump_write);
 665
 666int dump_seek(struct file *file, loff_t off)
 667{
 668        int ret = 1;
 669
 670        if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
 671                if (file->f_op->llseek(file, off, SEEK_CUR) < 0)
 672                        return 0;
 673        } else {
 674                char *buf = (char *)get_zeroed_page(GFP_KERNEL);
 675
 676                if (!buf)
 677                        return 0;
 678                while (off > 0) {
 679                        unsigned long n = off;
 680
 681                        if (n > PAGE_SIZE)
 682                                n = PAGE_SIZE;
 683                        if (!dump_write(file, buf, n)) {
 684                                ret = 0;
 685                                break;
 686                        }
 687                        off -= n;
 688                }
 689                free_page((unsigned long)buf);
 690        }
 691        return ret;
 692}
 693EXPORT_SYMBOL(dump_seek);
 694
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