fs/coredump.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/slab.h>
   3 #include <linux/file.h>
   4 #include <linux/fdtable.h>
   5 #include <linux/freezer.h>
   6 #include <linux/mm.h>
   7 #include <linux/stat.h>
   8 #include <linux/fcntl.h>
   9 #include <linux/swap.h>
  10 #include <linux/ctype.h>
  11 #include <linux/string.h>
  12 #include <linux/init.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/perf_event.h>
  15 #include <linux/highmem.h>
  16 #include <linux/spinlock.h>
  17 #include <linux/key.h>
  18 #include <linux/personality.h>
  19 #include <linux/binfmts.h>
  20 #include <linux/coredump.h>
  21 #include <linux/sched/coredump.h>
  22 #include <linux/sched/signal.h>
  23 #include <linux/sched/task_stack.h>
  24 #include <linux/utsname.h>
  25 #include <linux/pid_namespace.h>
  26 #include <linux/module.h>
  27 #include <linux/namei.h>
  28 #include <linux/mount.h>
  29 #include <linux/security.h>
  30 #include <linux/syscalls.h>
  31 #include <linux/tsacct_kern.h>
  32 #include <linux/cn_proc.h>
  33 #include <linux/audit.h>
  34 #include <linux/kmod.h>
  35 #include <linux/fsnotify.h>
  36 #include <linux/fs_struct.h>
  37 #include <linux/pipe_fs_i.h>
  38 #include <linux/oom.h>
  39 #include <linux/compat.h>
  40 #include <linux/fs.h>
  41 #include <linux/path.h>
  42 #include <linux/timekeeping.h>
  43 #include <linux/sysctl.h>
  44 #include <linux/elf.h>
  45
  46 #include <linux/uaccess.h>
  47 #include <asm/mmu_context.h>
  48 #include <asm/tlb.h>
  49 #include <asm/exec.h>
  50
  51 #include <trace/events/task.h>
  52 #include "internal.h"
  53
  54 #include <trace/events/sched.h>
  55
  56 static bool dump_vma_snapshot(struct coredump_params *cprm);
  57 static void free_vma_snapshot(struct coredump_params *cprm);
  58
  59 static int core_uses_pid;
  60 static unsigned int core_pipe_limit;
  61 static char core_pattern[CORENAME_MAX_SIZE] = "core";
  62 static int core_name_size = CORENAME_MAX_SIZE;
  63
  64 struct core_name {
  65         char *corename;
  66         int used, size;
  67 };
  68
  69 static int expand_corename(struct core_name *cn, int size)
  70 {
  71         char *corename = krealloc(cn->corename, size, GFP_KERNEL);
  72
  73         if (!corename)
  74                 return -ENOMEM;
  75
  76         if (size > core_name_size) /* racy but harmless */
  77                 core_name_size = size;
  78
  79         cn->size = ksize(corename);
  80         cn->corename = corename;
  81         return 0;
  82 }
  83
  84 static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
  85                                      va_list arg)
  86 {
  87         int free, need;
  88         va_list arg_copy;
  89
  90 again:
  91         free = cn->size - cn->used;
  92
  93         va_copy(arg_copy, arg);
  94         need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
  95         va_end(arg_copy);
  96
  97         if (need < free) {
  98                 cn->used += need;
  99                 return 0;
 100         }
 101
 102         if (!expand_corename(cn, cn->size + need - free + 1))
 103                 goto again;
 104
 105         return -ENOMEM;
 106 }
 107
 108 static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
 109 {
 110         va_list arg;
 111         int ret;
 112
 113         va_start(arg, fmt);
 114         ret = cn_vprintf(cn, fmt, arg);
 115         va_end(arg);
 116
 117         return ret;
 118 }
 119
 120 static __printf(2, 3)
 121 int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
 122 {
 123         int cur = cn->used;
 124         va_list arg;
 125         int ret;
 126
 127         va_start(arg, fmt);
 128         ret = cn_vprintf(cn, fmt, arg);
 129         va_end(arg);
 130
 131         if (ret == 0) {
 132                 /*
 133                  * Ensure that this coredump name component can't cause the
 134                  * resulting corefile path to consist of a ".." or ".".
 135                  */
 136                 if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
 137                                 (cn->used - cur == 2 && cn->corename[cur] == '.'
 138                                 && cn->corename[cur+1] == '.'))
 139                         cn->corename[cur] = '!';
 140
 141                 /*
 142                  * Empty names are fishy and could be used to create a "//" in a
 143                  * corefile name, causing the coredump to happen one directory
 144                  * level too high. Enforce that all components of the core
 145                  * pattern are at least one character long.
 146                  */
 147                 if (cn->used == cur)
 148                         ret = cn_printf(cn, "!");
 149         }
 150
 151         for (; cur < cn->used; ++cur) {
 152                 if (cn->corename[cur] == '/')
 153                         cn->corename[cur] = '!';
 154         }
 155         return ret;
 156 }
 157
 158 static int cn_print_exe_file(struct core_name *cn, bool name_only)
 159 {
 160         struct file *exe_file;
 161         char *pathbuf, *path, *ptr;
 162         int ret;
 163
 164         exe_file = get_mm_exe_file(current->mm);
 165         if (!exe_file)
 166                 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
 167
 168         pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
 169         if (!pathbuf) {
 170                 ret = -ENOMEM;
 171                 goto put_exe_file;
 172         }
 173
 174         path = file_path(exe_file, pathbuf, PATH_MAX);
 175         if (IS_ERR(path)) {
 176                 ret = PTR_ERR(path);
 177                 goto free_buf;
 178         }
 179
 180         if (name_only) {
 181                 ptr = strrchr(path, '/');
 182                 if (ptr)
 183                         path = ptr + 1;
 184         }
 185         ret = cn_esc_printf(cn, "%s", path);
 186
 187 free_buf:
 188         kfree(pathbuf);
 189 put_exe_file:
 190         fput(exe_file);
 191         return ret;
 192 }
 193
 194 /* format_corename will inspect the pattern parameter, and output a
 195  * name into corename, which must have space for at least
 196  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
 197  */
 198 static int format_corename(struct core_name *cn, struct coredump_params *cprm,
 199                            size_t **argv, int *argc)
 200 {
 201         const struct cred *cred = current_cred();
 202         const char *pat_ptr = core_pattern;
 203         int ispipe = (*pat_ptr == '|');
 204         bool was_space = false;
 205         int pid_in_pattern = 0;
 206         int err = 0;
 207
 208         cn->used = 0;
 209         cn->corename = NULL;
 210         if (expand_corename(cn, core_name_size))
 211                 return -ENOMEM;
 212         cn->corename[0] = '\0';
 213
 214         if (ispipe) {
 215                 int argvs = sizeof(core_pattern) / 2;
 216                 (*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
 217                 if (!(*argv))
 218                         return -ENOMEM;
 219                 (*argv)[(*argc)++] = 0;
 220                 ++pat_ptr;
 221                 if (!(*pat_ptr))
 222                         return -ENOMEM;
 223         }
 224
 225         /* Repeat as long as we have more pattern to process and more output
 226            space */
 227         while (*pat_ptr) {
 228                 /*
 229                  * Split on spaces before doing template expansion so that
 230                  * %e and %E don't get split if they have spaces in them
 231                  */
 232                 if (ispipe) {
 233                         if (isspace(*pat_ptr)) {
 234                                 if (cn->used != 0)
 235                                         was_space = true;
 236                                 pat_ptr++;
 237                                 continue;
 238                         } else if (was_space) {
 239                                 was_space = false;
 240                                 err = cn_printf(cn, "%c", '\0');
 241                                 if (err)
 242                                         return err;
 243                                 (*argv)[(*argc)++] = cn->used;
 244                         }
 245                 }
 246                 if (*pat_ptr != '%') {
 247                         err = cn_printf(cn, "%c", *pat_ptr++);
 248                 } else {
 249                         switch (*++pat_ptr) {
 250                         /* single % at the end, drop that */
 251                         case 0:
 252                                 goto out;
 253                         /* Double percent, output one percent */
 254                         case '%':
 255                                 err = cn_printf(cn, "%c", '%');
 256                                 break;
 257                         /* pid */
 258                         case 'p':
 259                                 pid_in_pattern = 1;
 260                                 err = cn_printf(cn, "%d",
 261                                               task_tgid_vnr(current));
 262                                 break;
 263                         /* global pid */
 264                         case 'P':
 265                                 err = cn_printf(cn, "%d",
 266                                               task_tgid_nr(current));
 267                                 break;
 268                         case 'i':
 269                                 err = cn_printf(cn, "%d",
 270                                               task_pid_vnr(current));
 271                                 break;
 272                         case 'I':
 273                                 err = cn_printf(cn, "%d",
 274                                               task_pid_nr(current));
 275                                 break;
 276                         /* uid */
 277                         case 'u':
 278                                 err = cn_printf(cn, "%u",
 279                                                 from_kuid(&init_user_ns,
 280                                                           cred->uid));
 281                                 break;
 282                         /* gid */
 283                         case 'g':
 284                                 err = cn_printf(cn, "%u",
 285                                                 from_kgid(&init_user_ns,
 286                                                           cred->gid));
 287                                 break;
 288                         case 'd':
 289                                 err = cn_printf(cn, "%d",
 290                                         __get_dumpable(cprm->mm_flags));
 291                                 break;
 292                         /* signal that caused the coredump */
 293                         case 's':
 294                                 err = cn_printf(cn, "%d",
 295                                                 cprm->siginfo->si_signo);
 296                                 break;
 297                         /* UNIX time of coredump */
 298                         case 't': {
 299                                 time64_t time;
 300
 301                                 time = ktime_get_real_seconds();
 302                                 err = cn_printf(cn, "%lld", time);
 303                                 break;
 304                         }
 305                         /* hostname */
 306                         case 'h':
 307                                 down_read(&uts_sem);
 308                                 err = cn_esc_printf(cn, "%s",
 309                                               utsname()->nodename);
 310                                 up_read(&uts_sem);
 311                                 break;
 312                         /* executable, could be changed by prctl PR_SET_NAME etc */
 313                         case 'e':
 314                                 err = cn_esc_printf(cn, "%s", current->comm);
 315                                 break;
 316                         /* file name of executable */
 317                         case 'f':
 318                                 err = cn_print_exe_file(cn, true);
 319                                 break;
 320                         case 'E':
 321                                 err = cn_print_exe_file(cn, false);
 322                                 break;
 323                         /* core limit size */
 324                         case 'c':
 325                                 err = cn_printf(cn, "%lu",
 326                                               rlimit(RLIMIT_CORE));
 327                                 break;
 328                         default:
 329                                 break;
 330                         }
 331                         ++pat_ptr;
 332                 }
 333
 334                 if (err)
 335                         return err;
 336         }
 337
 338 out:
 339         /* Backward compatibility with core_uses_pid:
 340          *
 341          * If core_pattern does not include a %p (as is the default)
 342          * and core_uses_pid is set, then .%pid will be appended to
 343          * the filename. Do not do this for piped commands. */
 344         if (!ispipe && !pid_in_pattern && core_uses_pid) {
 345                 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
 346                 if (err)
 347                         return err;
 348         }
 349         return ispipe;
 350 }
 351
 352 static int zap_process(struct task_struct *start, int exit_code)
 353 {
 354         struct task_struct *t;
 355         int nr = 0;
 356
 357         /* ignore all signals except SIGKILL, see prepare_signal() */
 358         start->signal->flags = SIGNAL_GROUP_EXIT;
 359         start->signal->group_exit_code = exit_code;
 360         start->signal->group_stop_count = 0;
 361
 362         for_each_thread(start, t) {
 363                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
 364                 if (t != current && !(t->flags & PF_POSTCOREDUMP)) {
 365                         sigaddset(&t->pending.signal, SIGKILL);
 366                         signal_wake_up(t, 1);
 367                         nr++;
 368                 }
 369         }
 370
 371         return nr;
 372 }
 373
 374 static int zap_threads(struct task_struct *tsk,
 375                         struct core_state *core_state, int exit_code)
 376 {
 377         struct signal_struct *signal = tsk->signal;
 378         int nr = -EAGAIN;
 379
 380         spin_lock_irq(&tsk->sighand->siglock);
 381         if (!(signal->flags & SIGNAL_GROUP_EXIT) && !signal->group_exec_task) {
 382                 signal->core_state = core_state;
 383                 nr = zap_process(tsk, exit_code);
 384                 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
 385                 tsk->flags |= PF_DUMPCORE;
 386                 atomic_set(&core_state->nr_threads, nr);
 387         }
 388         spin_unlock_irq(&tsk->sighand->siglock);
 389         return nr;
 390 }
 391
 392 static int coredump_wait(int exit_code, struct core_state *core_state)
 393 {
 394         struct task_struct *tsk = current;
 395         int core_waiters = -EBUSY;
 396
 397         init_completion(&core_state->startup);
 398         core_state->dumper.task = tsk;
 399         core_state->dumper.next = NULL;
 400
 401         core_waiters = zap_threads(tsk, core_state, exit_code);
 402         if (core_waiters > 0) {
 403                 struct core_thread *ptr;
 404
 405                 freezer_do_not_count();
 406                 wait_for_completion(&core_state->startup);
 407                 freezer_count();
 408                 /*
 409                  * Wait for all the threads to become inactive, so that
 410                  * all the thread context (extended register state, like
 411                  * fpu etc) gets copied to the memory.
 412                  */
 413                 ptr = core_state->dumper.next;
 414                 while (ptr != NULL) {
 415                         wait_task_inactive(ptr->task, 0);
 416                         ptr = ptr->next;
 417                 }
 418         }
 419
 420         return core_waiters;
 421 }
 422
 423 static void coredump_finish(bool core_dumped)
 424 {
 425         struct core_thread *curr, *next;
 426         struct task_struct *task;
 427
 428         spin_lock_irq(&current->sighand->siglock);
 429         if (core_dumped && !__fatal_signal_pending(current))
 430                 current->signal->group_exit_code |= 0x80;
 431         next = current->signal->core_state->dumper.next;
 432         current->signal->core_state = NULL;
 433         spin_unlock_irq(&current->sighand->siglock);
 434
 435         while ((curr = next) != NULL) {
 436                 next = curr->next;
 437                 task = curr->task;
 438                 /*
 439                  * see coredump_task_exit(), curr->task must not see
 440                  * ->task == NULL before we read ->next.
 441                  */
 442                 smp_mb();
 443                 curr->task = NULL;
 444                 wake_up_process(task);
 445         }
 446 }
 447
 448 static bool dump_interrupted(void)
 449 {
 450         /*
 451          * SIGKILL or freezing() interrupt the coredumping. Perhaps we
 452          * can do try_to_freeze() and check __fatal_signal_pending(),
 453          * but then we need to teach dump_write() to restart and clear
 454          * TIF_SIGPENDING.
 455          */
 456         return fatal_signal_pending(current) || freezing(current);
 457 }
 458
 459 static void wait_for_dump_helpers(struct file *file)
 460 {
 461         struct pipe_inode_info *pipe = file->private_data;
 462
 463         pipe_lock(pipe);
 464         pipe->readers++;
 465         pipe->writers--;
 466         wake_up_interruptible_sync(&pipe->rd_wait);
 467         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 468         pipe_unlock(pipe);
 469
 470         /*
 471          * We actually want wait_event_freezable() but then we need
 472          * to clear TIF_SIGPENDING and improve dump_interrupted().
 473          */
 474         wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
 475
 476         pipe_lock(pipe);
 477         pipe->readers--;
 478         pipe->writers++;
 479         pipe_unlock(pipe);
 480 }
 481
 482 /*
 483  * umh_pipe_setup
 484  * helper function to customize the process used
 485  * to collect the core in userspace.  Specifically
 486  * it sets up a pipe and installs it as fd 0 (stdin)
 487  * for the process.  Returns 0 on success, or
 488  * PTR_ERR on failure.
 489  * Note that it also sets the core limit to 1.  This
 490  * is a special value that we use to trap recursive
 491  * core dumps
 492  */
 493 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
 494 {
 495         struct file *files[2];
 496         struct coredump_params *cp = (struct coredump_params *)info->data;
 497         int err = create_pipe_files(files, 0);
 498         if (err)
 499                 return err;
 500
 501         cp->file = files[1];
 502
 503         err = replace_fd(0, files[0], 0);
 504         fput(files[0]);
 505         /* and disallow core files too */
 506         current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
 507
 508         return err;
 509 }
 510
 511 void do_coredump(const kernel_siginfo_t *siginfo)
 512 {
 513         struct core_state core_state;
 514         struct core_name cn;
 515         struct mm_struct *mm = current->mm;
 516         struct linux_binfmt * binfmt;
 517         const struct cred *old_cred;
 518         struct cred *cred;
 519         int retval = 0;
 520         int ispipe;
 521         size_t *argv = NULL;
 522         int argc = 0;
 523         /* require nonrelative corefile path and be extra careful */
 524         bool need_suid_safe = false;
 525         bool core_dumped = false;
 526         static atomic_t core_dump_count = ATOMIC_INIT(0);
 527         struct coredump_params cprm = {
 528                 .siginfo = siginfo,
 529                 .regs = signal_pt_regs(),
 530                 .limit = rlimit(RLIMIT_CORE),
 531                 /*
 532                  * We must use the same mm->flags while dumping core to avoid
 533                  * inconsistency of bit flags, since this flag is not protected
 534                  * by any locks.
 535                  */
 536                 .mm_flags = mm->flags,
 537                 .vma_meta = NULL,
 538         };
 539
 540         audit_core_dumps(siginfo->si_signo);
 541
 542         binfmt = mm->binfmt;
 543         if (!binfmt || !binfmt->core_dump)
 544                 goto fail;
 545         if (!__get_dumpable(cprm.mm_flags))
 546                 goto fail;
 547
 548         cred = prepare_creds();
 549         if (!cred)
 550                 goto fail;
 551         /*
 552          * We cannot trust fsuid as being the "true" uid of the process
 553          * nor do we know its entire history. We only know it was tainted
 554          * so we dump it as root in mode 2, and only into a controlled
 555          * environment (pipe handler or fully qualified path).
 556          */
 557         if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
 558                 /* Setuid core dump mode */
 559                 cred->fsuid = GLOBAL_ROOT_UID;  /* Dump root private */
 560                 need_suid_safe = true;
 561         }
 562
 563         retval = coredump_wait(siginfo->si_signo, &core_state);
 564         if (retval < 0)
 565                 goto fail_creds;
 566
 567         old_cred = override_creds(cred);
 568
 569         ispipe = format_corename(&cn, &cprm, &argv, &argc);
 570
 571         if (ispipe) {
 572                 int argi;
 573                 int dump_count;
 574                 char **helper_argv;
 575                 struct subprocess_info *sub_info;
 576
 577                 if (ispipe < 0) {
 578                         printk(KERN_WARNING "format_corename failed\n");
 579                         printk(KERN_WARNING "Aborting core\n");
 580                         goto fail_unlock;
 581                 }
 582
 583                 if (cprm.limit == 1) {
 584                         /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
 585                          *
 586                          * Normally core limits are irrelevant to pipes, since
 587                          * we're not writing to the file system, but we use
 588                          * cprm.limit of 1 here as a special value, this is a
 589                          * consistent way to catch recursive crashes.
 590                          * We can still crash if the core_pattern binary sets
 591                          * RLIM_CORE = !1, but it runs as root, and can do
 592                          * lots of stupid things.
 593                          *
 594                          * Note that we use task_tgid_vnr here to grab the pid
 595                          * of the process group leader.  That way we get the
 596                          * right pid if a thread in a multi-threaded
 597                          * core_pattern process dies.
 598                          */
 599                         printk(KERN_WARNING
 600                                 "Process %d(%s) has RLIMIT_CORE set to 1\n",
 601                                 task_tgid_vnr(current), current->comm);
 602                         printk(KERN_WARNING "Aborting core\n");
 603                         goto fail_unlock;
 604                 }
 605                 cprm.limit = RLIM_INFINITY;
 606
 607                 dump_count = atomic_inc_return(&core_dump_count);
 608                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
 609                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
 610                                task_tgid_vnr(current), current->comm);
 611                         printk(KERN_WARNING "Skipping core dump\n");
 612                         goto fail_dropcount;
 613                 }
 614
 615                 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
 616                                             GFP_KERNEL);
 617                 if (!helper_argv) {
 618                         printk(KERN_WARNING "%s failed to allocate memory\n",
 619                                __func__);
 620                         goto fail_dropcount;
 621                 }
 622                 for (argi = 0; argi < argc; argi++)
 623                         helper_argv[argi] = cn.corename + argv[argi];
 624                 helper_argv[argi] = NULL;
 625
 626                 retval = -ENOMEM;
 627                 sub_info = call_usermodehelper_setup(helper_argv[0],
 628                                                 helper_argv, NULL, GFP_KERNEL,
 629                                                 umh_pipe_setup, NULL, &cprm);
 630                 if (sub_info)
 631                         retval = call_usermodehelper_exec(sub_info,
 632                                                           UMH_WAIT_EXEC);
 633
 634                 kfree(helper_argv);
 635                 if (retval) {
 636                         printk(KERN_INFO "Core dump to |%s pipe failed\n",
 637                                cn.corename);
 638                         goto close_fail;
 639                 }
 640         } else {
 641                 struct user_namespace *mnt_userns;
 642                 struct inode *inode;
 643                 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
 644                                  O_LARGEFILE | O_EXCL;
 645
 646                 if (cprm.limit < binfmt->min_coredump)
 647                         goto fail_unlock;
 648
 649                 if (need_suid_safe && cn.corename[0] != '/') {
 650                         printk(KERN_WARNING "Pid %d(%s) can only dump core "\
 651                                 "to fully qualified path!\n",
 652                                 task_tgid_vnr(current), current->comm);
 653                         printk(KERN_WARNING "Skipping core dump\n");
 654                         goto fail_unlock;
 655                 }
 656
 657                 /*
 658                  * Unlink the file if it exists unless this is a SUID
 659                  * binary - in that case, we're running around with root
 660                  * privs and don't want to unlink another user's coredump.
 661                  */
 662                 if (!need_suid_safe) {
 663                         /*
 664                          * If it doesn't exist, that's fine. If there's some
 665                          * other problem, we'll catch it at the filp_open().
 666                          */
 667                         do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
 668                 }
 669
 670                 /*
 671                  * There is a race between unlinking and creating the
 672                  * file, but if that causes an EEXIST here, that's
 673                  * fine - another process raced with us while creating
 674                  * the corefile, and the other process won. To userspace,
 675                  * what matters is that at least one of the two processes
 676                  * writes its coredump successfully, not which one.
 677                  */
 678                 if (need_suid_safe) {
 679                         /*
 680                          * Using user namespaces, normal user tasks can change
 681                          * their current->fs->root to point to arbitrary
 682                          * directories. Since the intention of the "only dump
 683                          * with a fully qualified path" rule is to control where
 684                          * coredumps may be placed using root privileges,
 685                          * current->fs->root must not be used. Instead, use the
 686                          * root directory of init_task.
 687                          */
 688                         struct path root;
 689
 690                         task_lock(&init_task);
 691                         get_fs_root(init_task.fs, &root);
 692                         task_unlock(&init_task);
 693                         cprm.file = file_open_root(&root, cn.corename,
 694                                                    open_flags, 0600);
 695                         path_put(&root);
 696                 } else {
 697                         cprm.file = filp_open(cn.corename, open_flags, 0600);
 698                 }
 699                 if (IS_ERR(cprm.file))
 700                         goto fail_unlock;
 701
 702                 inode = file_inode(cprm.file);
 703                 if (inode->i_nlink > 1)
 704                         goto close_fail;
 705                 if (d_unhashed(cprm.file->f_path.dentry))
 706                         goto close_fail;
 707                 /*
 708                  * AK: actually i see no reason to not allow this for named
 709                  * pipes etc, but keep the previous behaviour for now.
 710                  */
 711                 if (!S_ISREG(inode->i_mode))
 712                         goto close_fail;
 713                 /*
 714                  * Don't dump core if the filesystem changed owner or mode
 715                  * of the file during file creation. This is an issue when
 716                  * a process dumps core while its cwd is e.g. on a vfat
 717                  * filesystem.
 718                  */
 719                 mnt_userns = file_mnt_user_ns(cprm.file);
 720                 if (!uid_eq(i_uid_into_mnt(mnt_userns, inode),
 721                             current_fsuid())) {
 722                         pr_info_ratelimited("Core dump to %s aborted: cannot preserve file owner\n",
 723                                             cn.corename);
 724                         goto close_fail;
 725                 }
 726                 if ((inode->i_mode & 0677) != 0600) {
 727                         pr_info_ratelimited("Core dump to %s aborted: cannot preserve file permissions\n",
 728                                             cn.corename);
 729                         goto close_fail;
 730                 }
 731                 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
 732                         goto close_fail;
 733                 if (do_truncate(mnt_userns, cprm.file->f_path.dentry,
 734                                 0, 0, cprm.file))
 735                         goto close_fail;
 736         }
 737
 738         /* get us an unshared descriptor table; almost always a no-op */
 739         /* The cell spufs coredump code reads the file descriptor tables */
 740         retval = unshare_files();
 741         if (retval)
 742                 goto close_fail;
 743         if (!dump_interrupted()) {
 744                 /*
 745                  * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
 746                  * have this set to NULL.
 747                  */
 748                 if (!cprm.file) {
 749                         pr_info("Core dump to |%s disabled\n", cn.corename);
 750                         goto close_fail;
 751                 }
 752                 if (!dump_vma_snapshot(&cprm))
 753                         goto close_fail;
 754
 755                 file_start_write(cprm.file);
 756                 core_dumped = binfmt->core_dump(&cprm);
 757                 /*
 758                  * Ensures that file size is big enough to contain the current
 759                  * file postion. This prevents gdb from complaining about
 760                  * a truncated file if the last "write" to the file was
 761                  * dump_skip.
 762                  */
 763                 if (cprm.to_skip) {
 764                         cprm.to_skip--;
 765                         dump_emit(&cprm, "", 1);
 766                 }
 767                 file_end_write(cprm.file);
 768                 free_vma_snapshot(&cprm);
 769         }
 770         if (ispipe && core_pipe_limit)
 771                 wait_for_dump_helpers(cprm.file);
 772 close_fail:
 773         if (cprm.file)
 774                 filp_close(cprm.file, NULL);
 775 fail_dropcount:
 776         if (ispipe)
 777                 atomic_dec(&core_dump_count);
 778 fail_unlock:
 779         kfree(argv);
 780         kfree(cn.corename);
 781         coredump_finish(core_dumped);
 782         revert_creds(old_cred);
 783 fail_creds:
 784         put_cred(cred);
 785 fail:
 786         return;
 787 }
 788
 789 /*
 790  * Core dumping helper functions.  These are the only things you should
 791  * do on a core-file: use only these functions to write out all the
 792  * necessary info.
 793  */
 794 static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr)
 795 {
 796         struct file *file = cprm->file;
 797         loff_t pos = file->f_pos;
 798         ssize_t n;
 799         if (cprm->written + nr > cprm->limit)
 800                 return 0;
 801
 802
 803         if (dump_interrupted())
 804                 return 0;
 805         n = __kernel_write(file, addr, nr, &pos);
 806         if (n != nr)
 807                 return 0;
 808         file->f_pos = pos;
 809         cprm->written += n;
 810         cprm->pos += n;
 811
 812         return 1;
 813 }
 814
 815 static int __dump_skip(struct coredump_params *cprm, size_t nr)
 816 {
 817         static char zeroes[PAGE_SIZE];
 818         struct file *file = cprm->file;
 819         if (file->f_mode & FMODE_LSEEK) {
 820                 if (dump_interrupted() ||
 821                     vfs_llseek(file, nr, SEEK_CUR) < 0)
 822                         return 0;
 823                 cprm->pos += nr;
 824                 return 1;
 825         } else {
 826                 while (nr > PAGE_SIZE) {
 827                         if (!__dump_emit(cprm, zeroes, PAGE_SIZE))
 828                                 return 0;
 829                         nr -= PAGE_SIZE;
 830                 }
 831                 return __dump_emit(cprm, zeroes, nr);
 832         }
 833 }
 834
 835 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
 836 {
 837         if (cprm->to_skip) {
 838                 if (!__dump_skip(cprm, cprm->to_skip))
 839                         return 0;
 840                 cprm->to_skip = 0;
 841         }
 842         return __dump_emit(cprm, addr, nr);
 843 }
 844 EXPORT_SYMBOL(dump_emit);
 845
 846 void dump_skip_to(struct coredump_params *cprm, unsigned long pos)
 847 {
 848         cprm->to_skip = pos - cprm->pos;
 849 }
 850 EXPORT_SYMBOL(dump_skip_to);
 851
 852 void dump_skip(struct coredump_params *cprm, size_t nr)
 853 {
 854         cprm->to_skip += nr;
 855 }
 856 EXPORT_SYMBOL(dump_skip);
 857
 858 #ifdef CONFIG_ELF_CORE
 859 int dump_user_range(struct coredump_params *cprm, unsigned long start,
 860                     unsigned long len)
 861 {
 862         unsigned long addr;
 863
 864         for (addr = start; addr < start + len; addr += PAGE_SIZE) {
 865                 struct page *page;
 866                 int stop;
 867
 868                 /*
 869                  * To avoid having to allocate page tables for virtual address
 870                  * ranges that have never been used yet, and also to make it
 871                  * easy to generate sparse core files, use a helper that returns
 872                  * NULL when encountering an empty page table entry that would
 873                  * otherwise have been filled with the zero page.
 874                  */
 875                 page = get_dump_page(addr);
 876                 if (page) {
 877                         void *kaddr = kmap_local_page(page);
 878
 879                         stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
 880                         kunmap_local(kaddr);
 881                         put_page(page);
 882                         if (stop)
 883                                 return 0;
 884                 } else {
 885                         dump_skip(cprm, PAGE_SIZE);
 886                 }
 887         }
 888         return 1;
 889 }
 890 #endif
 891
 892 int dump_align(struct coredump_params *cprm, int align)
 893 {
 894         unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1);
 895         if (align & (align - 1))
 896                 return 0;
 897         if (mod)
 898                 cprm->to_skip += align - mod;
 899         return 1;
 900 }
 901 EXPORT_SYMBOL(dump_align);
 902
 903 #ifdef CONFIG_SYSCTL
 904
 905 void validate_coredump_safety(void)
 906 {
 907         if (suid_dumpable == SUID_DUMP_ROOT &&
 908             core_pattern[0] != '/' && core_pattern[0] != '|') {
 909                 pr_warn(
 910 "Unsafe core_pattern used with fs.suid_dumpable=2.\n"
 911 "Pipe handler or fully qualified core dump path required.\n"
 912 "Set kernel.core_pattern before fs.suid_dumpable.\n"
 913                 );
 914         }
 915 }
 916
 917 static int proc_dostring_coredump(struct ctl_table *table, int write,
 918                   void *buffer, size_t *lenp, loff_t *ppos)
 919 {
 920         int error = proc_dostring(table, write, buffer, lenp, ppos);
 921
 922         if (!error)
 923                 validate_coredump_safety();
 924         return error;
 925 }
 926
 927 static struct ctl_table coredump_sysctls[] = {
 928         {
 929                 .procname       = "core_uses_pid",
 930                 .data           = &core_uses_pid,
 931                 .maxlen         = sizeof(int),
 932                 .mode           = 0644,
 933                 .proc_handler   = proc_dointvec,
 934         },
 935         {
 936                 .procname       = "core_pattern",
 937                 .data           = core_pattern,
 938                 .maxlen         = CORENAME_MAX_SIZE,
 939                 .mode           = 0644,
 940                 .proc_handler   = proc_dostring_coredump,
 941         },
 942         {
 943                 .procname       = "core_pipe_limit",
 944                 .data           = &core_pipe_limit,
 945                 .maxlen         = sizeof(unsigned int),
 946                 .mode           = 0644,
 947                 .proc_handler   = proc_dointvec,
 948         },
 949         { }
 950 };
 951
 952 static int __init init_fs_coredump_sysctls(void)
 953 {
 954         register_sysctl_init("kernel", coredump_sysctls);
 955         return 0;
 956 }
 957 fs_initcall(init_fs_coredump_sysctls);
 958 #endif /* CONFIG_SYSCTL */
 959
 960 /*
 961  * The purpose of always_dump_vma() is to make sure that special kernel mappings
 962  * that are useful for post-mortem analysis are included in every core dump.
 963  * In that way we ensure that the core dump is fully interpretable later
 964  * without matching up the same kernel and hardware config to see what PC values
 965  * meant. These special mappings include - vDSO, vsyscall, and other
 966  * architecture specific mappings
 967  */
 968 static bool always_dump_vma(struct vm_area_struct *vma)
 969 {
 970         /* Any vsyscall mappings? */
 971         if (vma == get_gate_vma(vma->vm_mm))
 972                 return true;
 973
 974         /*
 975          * Assume that all vmas with a .name op should always be dumped.
 976          * If this changes, a new vm_ops field can easily be added.
 977          */
 978         if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
 979                 return true;
 980
 981         /*
 982          * arch_vma_name() returns non-NULL for special architecture mappings,
 983          * such as vDSO sections.
 984          */
 985         if (arch_vma_name(vma))
 986                 return true;
 987
 988         return false;
 989 }
 990
 991 #define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1
 992
 993 /*
 994  * Decide how much of @vma's contents should be included in a core dump.
 995  */
 996 static unsigned long vma_dump_size(struct vm_area_struct *vma,
 997                                    unsigned long mm_flags)
 998 {
 999 #define FILTER(type)    (mm_flags & (1UL << MMF_DUMP_##type))
1000
1001         /* always dump the vdso and vsyscall sections */
1002         if (always_dump_vma(vma))
1003                 goto whole;
1004
1005         if (vma->vm_flags & VM_DONTDUMP)
1006                 return 0;
1007
1008         /* support for DAX */
1009         if (vma_is_dax(vma)) {
1010                 if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
1011                         goto whole;
1012                 if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
1013                         goto whole;
1014                 return 0;
1015         }
1016
1017         /* Hugetlb memory check */
1018         if (is_vm_hugetlb_page(vma)) {
1019                 if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
1020                         goto whole;
1021                 if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
1022                         goto whole;
1023                 return 0;
1024         }
1025
1026         /* Do not dump I/O mapped devices or special mappings */
1027         if (vma->vm_flags & VM_IO)
1028                 return 0;
1029
1030         /* By default, dump shared memory if mapped from an anonymous file. */
1031         if (vma->vm_flags & VM_SHARED) {
1032                 if (file_inode(vma->vm_file)->i_nlink == 0 ?
1033                     FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
1034                         goto whole;
1035                 return 0;
1036         }
1037
1038         /* Dump segments that have been written to.  */
1039         if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
1040                 goto whole;
1041         if (vma->vm_file == NULL)
1042                 return 0;
1043
1044         if (FILTER(MAPPED_PRIVATE))
1045                 goto whole;
1046
1047         /*
1048          * If this is the beginning of an executable file mapping,
1049          * dump the first page to aid in determining what was mapped here.
1050          */
1051         if (FILTER(ELF_HEADERS) &&
1052             vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
1053                 if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
1054                         return PAGE_SIZE;
1055
1056                 /*
1057                  * ELF libraries aren't always executable.
1058                  * We'll want to check whether the mapping starts with the ELF
1059                  * magic, but not now - we're holding the mmap lock,
1060                  * so copy_from_user() doesn't work here.
1061                  * Use a placeholder instead, and fix it up later in
1062                  * dump_vma_snapshot().
1063                  */
1064                 return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER;
1065         }
1066
1067 #undef  FILTER
1068
1069         return 0;
1070
1071 whole:
1072         return vma->vm_end - vma->vm_start;
1073 }
1074
1075 static struct vm_area_struct *first_vma(struct task_struct *tsk,
1076                                         struct vm_area_struct *gate_vma)
1077 {
1078         struct vm_area_struct *ret = tsk->mm->mmap;
1079
1080         if (ret)
1081                 return ret;
1082         return gate_vma;
1083 }
1084
1085 /*
1086  * Helper function for iterating across a vma list.  It ensures that the caller
1087  * will visit `gate_vma' prior to terminating the search.
1088  */
1089 static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
1090                                        struct vm_area_struct *gate_vma)
1091 {
1092         struct vm_area_struct *ret;
1093
1094         ret = this_vma->vm_next;
1095         if (ret)
1096                 return ret;
1097         if (this_vma == gate_vma)
1098                 return NULL;
1099         return gate_vma;
1100 }
1101
1102 static void free_vma_snapshot(struct coredump_params *cprm)
1103 {
1104         if (cprm->vma_meta) {
1105                 int i;
1106                 for (i = 0; i < cprm->vma_count; i++) {
1107                         struct file *file = cprm->vma_meta[i].file;
1108                         if (file)
1109                                 fput(file);
1110                 }
1111                 kvfree(cprm->vma_meta);
1112                 cprm->vma_meta = NULL;
1113         }
1114 }
1115
1116 /*
1117  * Under the mmap_lock, take a snapshot of relevant information about the task's
1118  * VMAs.
1119  */
1120 static bool dump_vma_snapshot(struct coredump_params *cprm)
1121 {
1122         struct vm_area_struct *vma, *gate_vma;
1123         struct mm_struct *mm = current->mm;
1124         int i;
1125
1126         /*
1127          * Once the stack expansion code is fixed to not change VMA bounds
1128          * under mmap_lock in read mode, this can be changed to take the
1129          * mmap_lock in read mode.
1130          */
1131         if (mmap_write_lock_killable(mm))
1132                 return false;
1133
1134         cprm->vma_data_size = 0;
1135         gate_vma = get_gate_vma(mm);
1136         cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0);
1137
1138         cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL);
1139         if (!cprm->vma_meta) {
1140                 mmap_write_unlock(mm);
1141                 return false;
1142         }
1143
1144         for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
1145                         vma = next_vma(vma, gate_vma), i++) {
1146                 struct core_vma_metadata *m = cprm->vma_meta + i;
1147
1148                 m->start = vma->vm_start;
1149                 m->end = vma->vm_end;
1150                 m->flags = vma->vm_flags;
1151                 m->dump_size = vma_dump_size(vma, cprm->mm_flags);
1152                 m->pgoff = vma->vm_pgoff;
1153
1154                 m->file = vma->vm_file;
1155                 if (m->file)
1156                         get_file(m->file);
1157         }
1158
1159         mmap_write_unlock(mm);
1160
1161         for (i = 0; i < cprm->vma_count; i++) {
1162                 struct core_vma_metadata *m = cprm->vma_meta + i;
1163
1164                 if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) {
1165                         char elfmag[SELFMAG];
1166
1167                         if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) ||
1168                                         memcmp(elfmag, ELFMAG, SELFMAG) != 0) {
1169                                 m->dump_size = 0;
1170                         } else {
1171                                 m->dump_size = PAGE_SIZE;
1172                         }
1173                 }
1174
1175                 cprm->vma_data_size += m->dump_size;
1176         }
1177
1178         return true;
1179 }