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/sort.h>
  22 #include <linux/sched/coredump.h>
  23 #include <linux/sched/signal.h>
  24 #include <linux/sched/task_stack.h>
  25 #include <linux/utsname.h>
  26 #include <linux/pid_namespace.h>
  27 #include <linux/module.h>
  28 #include <linux/namei.h>
  29 #include <linux/mount.h>
  30 #include <linux/security.h>
  31 #include <linux/syscalls.h>
  32 #include <linux/tsacct_kern.h>
  33 #include <linux/cn_proc.h>
  34 #include <linux/audit.h>
  35 #include <linux/kmod.h>
  36 #include <linux/fsnotify.h>
  37 #include <linux/fs_struct.h>
  38 #include <linux/pipe_fs_i.h>
  39 #include <linux/oom.h>
  40 #include <linux/compat.h>
  41 #include <linux/fs.h>
  42 #include <linux/path.h>
  43 #include <linux/timekeeping.h>
  44 #include <linux/sysctl.h>
  45 #include <linux/elf.h>
  46
  47 #include <linux/uaccess.h>
  48 #include <asm/mmu_context.h>
  49 #include <asm/tlb.h>
  50 #include <asm/exec.h>
  51
  52 #include <trace/events/task.h>
  53 #include "internal.h"
  54
  55 #include <trace/events/sched.h>
  56
  57 static bool dump_vma_snapshot(struct coredump_params *cprm);
  58 static void free_vma_snapshot(struct coredump_params *cprm);
  59
  60 #define CORE_FILE_NOTE_SIZE_DEFAULT (4*1024*1024)
  61 /* Define a reasonable max cap */
  62 #define CORE_FILE_NOTE_SIZE_MAX (16*1024*1024)
  63
  64 static int core_uses_pid;
  65 static unsigned int core_pipe_limit;
  66 static char core_pattern[CORENAME_MAX_SIZE] = "core";
  67 static int core_name_size = CORENAME_MAX_SIZE;
  68 unsigned int core_file_note_size_limit = CORE_FILE_NOTE_SIZE_DEFAULT;
  69
  70 struct core_name {
  71         char *corename;
  72         int used, size;
  73 };
  74
  75 static int expand_corename(struct core_name *cn, int size)
  76 {
  77         char *corename;
  78
  79         size = kmalloc_size_roundup(size);
  80         corename = krealloc(cn->corename, size, GFP_KERNEL);
  81
  82         if (!corename)
  83                 return -ENOMEM;
  84
  85         if (size > core_name_size) /* racy but harmless */
  86                 core_name_size = size;
  87
  88         cn->size = size;
  89         cn->corename = corename;
  90         return 0;
  91 }
  92
  93 static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
  94                                      va_list arg)
  95 {
  96         int free, need;
  97         va_list arg_copy;
  98
  99 again:
 100         free = cn->size - cn->used;
 101
 102         va_copy(arg_copy, arg);
 103         need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
 104         va_end(arg_copy);
 105
 106         if (need < free) {
 107                 cn->used += need;
 108                 return 0;
 109         }
 110
 111         if (!expand_corename(cn, cn->size + need - free + 1))
 112                 goto again;
 113
 114         return -ENOMEM;
 115 }
 116
 117 static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
 118 {
 119         va_list arg;
 120         int ret;
 121
 122         va_start(arg, fmt);
 123         ret = cn_vprintf(cn, fmt, arg);
 124         va_end(arg);
 125
 126         return ret;
 127 }
 128
 129 static __printf(2, 3)
 130 int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
 131 {
 132         int cur = cn->used;
 133         va_list arg;
 134         int ret;
 135
 136         va_start(arg, fmt);
 137         ret = cn_vprintf(cn, fmt, arg);
 138         va_end(arg);
 139
 140         if (ret == 0) {
 141                 /*
 142                  * Ensure that this coredump name component can't cause the
 143                  * resulting corefile path to consist of a ".." or ".".
 144                  */
 145                 if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
 146                                 (cn->used - cur == 2 && cn->corename[cur] == '.'
 147                                 && cn->corename[cur+1] == '.'))
 148                         cn->corename[cur] = '!';
 149
 150                 /*
 151                  * Empty names are fishy and could be used to create a "//" in a
 152                  * corefile name, causing the coredump to happen one directory
 153                  * level too high. Enforce that all components of the core
 154                  * pattern are at least one character long.
 155                  */
 156                 if (cn->used == cur)
 157                         ret = cn_printf(cn, "!");
 158         }
 159
 160         for (; cur < cn->used; ++cur) {
 161                 if (cn->corename[cur] == '/')
 162                         cn->corename[cur] = '!';
 163         }
 164         return ret;
 165 }
 166
 167 static int cn_print_exe_file(struct core_name *cn, bool name_only)
 168 {
 169         struct file *exe_file;
 170         char *pathbuf, *path, *ptr;
 171         int ret;
 172
 173         exe_file = get_mm_exe_file(current->mm);
 174         if (!exe_file)
 175                 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
 176
 177         pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
 178         if (!pathbuf) {
 179                 ret = -ENOMEM;
 180                 goto put_exe_file;
 181         }
 182
 183         path = file_path(exe_file, pathbuf, PATH_MAX);
 184         if (IS_ERR(path)) {
 185                 ret = PTR_ERR(path);
 186                 goto free_buf;
 187         }
 188
 189         if (name_only) {
 190                 ptr = strrchr(path, '/');
 191                 if (ptr)
 192                         path = ptr + 1;
 193         }
 194         ret = cn_esc_printf(cn, "%s", path);
 195
 196 free_buf:
 197         kfree(pathbuf);
 198 put_exe_file:
 199         fput(exe_file);
 200         return ret;
 201 }
 202
 203 /* format_corename will inspect the pattern parameter, and output a
 204  * name into corename, which must have space for at least
 205  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
 206  */
 207 static int format_corename(struct core_name *cn, struct coredump_params *cprm,
 208                            size_t **argv, int *argc)
 209 {
 210         const struct cred *cred = current_cred();
 211         const char *pat_ptr = core_pattern;
 212         int ispipe = (*pat_ptr == '|');
 213         bool was_space = false;
 214         int pid_in_pattern = 0;
 215         int err = 0;
 216
 217         cn->used = 0;
 218         cn->corename = NULL;
 219         if (expand_corename(cn, core_name_size))
 220                 return -ENOMEM;
 221         cn->corename[0] = '\0';
 222
 223         if (ispipe) {
 224                 int argvs = sizeof(core_pattern) / 2;
 225                 (*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
 226                 if (!(*argv))
 227                         return -ENOMEM;
 228                 (*argv)[(*argc)++] = 0;
 229                 ++pat_ptr;
 230                 if (!(*pat_ptr))
 231                         return -ENOMEM;
 232         }
 233
 234         /* Repeat as long as we have more pattern to process and more output
 235            space */
 236         while (*pat_ptr) {
 237                 /*
 238                  * Split on spaces before doing template expansion so that
 239                  * %e and %E don't get split if they have spaces in them
 240                  */
 241                 if (ispipe) {
 242                         if (isspace(*pat_ptr)) {
 243                                 if (cn->used != 0)
 244                                         was_space = true;
 245                                 pat_ptr++;
 246                                 continue;
 247                         } else if (was_space) {
 248                                 was_space = false;
 249                                 err = cn_printf(cn, "%c", '\0');
 250                                 if (err)
 251                                         return err;
 252                                 (*argv)[(*argc)++] = cn->used;
 253                         }
 254                 }
 255                 if (*pat_ptr != '%') {
 256                         err = cn_printf(cn, "%c", *pat_ptr++);
 257                 } else {
 258                         switch (*++pat_ptr) {
 259                         /* single % at the end, drop that */
 260                         case 0:
 261                                 goto out;
 262                         /* Double percent, output one percent */
 263                         case '%':
 264                                 err = cn_printf(cn, "%c", '%');
 265                                 break;
 266                         /* pid */
 267                         case 'p':
 268                                 pid_in_pattern = 1;
 269                                 err = cn_printf(cn, "%d",
 270                                               task_tgid_vnr(current));
 271                                 break;
 272                         /* global pid */
 273                         case 'P':
 274                                 err = cn_printf(cn, "%d",
 275                                               task_tgid_nr(current));
 276                                 break;
 277                         case 'i':
 278                                 err = cn_printf(cn, "%d",
 279                                               task_pid_vnr(current));
 280                                 break;
 281                         case 'I':
 282                                 err = cn_printf(cn, "%d",
 283                                               task_pid_nr(current));
 284                                 break;
 285                         /* uid */
 286                         case 'u':
 287                                 err = cn_printf(cn, "%u",
 288                                                 from_kuid(&init_user_ns,
 289                                                           cred->uid));
 290                                 break;
 291                         /* gid */
 292                         case 'g':
 293                                 err = cn_printf(cn, "%u",
 294                                                 from_kgid(&init_user_ns,
 295                                                           cred->gid));
 296                                 break;
 297                         case 'd':
 298                                 err = cn_printf(cn, "%d",
 299                                         __get_dumpable(cprm->mm_flags));
 300                                 break;
 301                         /* signal that caused the coredump */
 302                         case 's':
 303                                 err = cn_printf(cn, "%d",
 304                                                 cprm->siginfo->si_signo);
 305                                 break;
 306                         /* UNIX time of coredump */
 307                         case 't': {
 308                                 time64_t time;
 309
 310                                 time = ktime_get_real_seconds();
 311                                 err = cn_printf(cn, "%lld", time);
 312                                 break;
 313                         }
 314                         /* hostname */
 315                         case 'h':
 316                                 down_read(&uts_sem);
 317                                 err = cn_esc_printf(cn, "%s",
 318                                               utsname()->nodename);
 319                                 up_read(&uts_sem);
 320                                 break;
 321                         /* executable, could be changed by prctl PR_SET_NAME etc */
 322                         case 'e':
 323                                 err = cn_esc_printf(cn, "%s", current->comm);
 324                                 break;
 325                         /* file name of executable */
 326                         case 'f':
 327                                 err = cn_print_exe_file(cn, true);
 328                                 break;
 329                         case 'E':
 330                                 err = cn_print_exe_file(cn, false);
 331                                 break;
 332                         /* core limit size */
 333                         case 'c':
 334                                 err = cn_printf(cn, "%lu",
 335                                               rlimit(RLIMIT_CORE));
 336                                 break;
 337                         /* CPU the task ran on */
 338                         case 'C':
 339                                 err = cn_printf(cn, "%d", cprm->cpu);
 340                                 break;
 341                         default:
 342                                 break;
 343                         }
 344                         ++pat_ptr;
 345                 }
 346
 347                 if (err)
 348                         return err;
 349         }
 350
 351 out:
 352         /* Backward compatibility with core_uses_pid:
 353          *
 354          * If core_pattern does not include a %p (as is the default)
 355          * and core_uses_pid is set, then .%pid will be appended to
 356          * the filename. Do not do this for piped commands. */
 357         if (!ispipe && !pid_in_pattern && core_uses_pid) {
 358                 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
 359                 if (err)
 360                         return err;
 361         }
 362         return ispipe;
 363 }
 364
 365 static int zap_process(struct signal_struct *signal, int exit_code)
 366 {
 367         struct task_struct *t;
 368         int nr = 0;
 369
 370         signal->flags = SIGNAL_GROUP_EXIT;
 371         signal->group_exit_code = exit_code;
 372         signal->group_stop_count = 0;
 373
 374         __for_each_thread(signal, t) {
 375                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
 376                 if (t != current && !(t->flags & PF_POSTCOREDUMP)) {
 377                         sigaddset(&t->pending.signal, SIGKILL);
 378                         signal_wake_up(t, 1);
 379                         nr++;
 380                 }
 381         }
 382
 383         return nr;
 384 }
 385
 386 static int zap_threads(struct task_struct *tsk,
 387                         struct core_state *core_state, int exit_code)
 388 {
 389         struct signal_struct *signal = tsk->signal;
 390         int nr = -EAGAIN;
 391
 392         spin_lock_irq(&tsk->sighand->siglock);
 393         if (!(signal->flags & SIGNAL_GROUP_EXIT) && !signal->group_exec_task) {
 394                 /* Allow SIGKILL, see prepare_signal() */
 395                 signal->core_state = core_state;
 396                 nr = zap_process(signal, exit_code);
 397                 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
 398                 tsk->flags |= PF_DUMPCORE;
 399                 atomic_set(&core_state->nr_threads, nr);
 400         }
 401         spin_unlock_irq(&tsk->sighand->siglock);
 402         return nr;
 403 }
 404
 405 static int coredump_wait(int exit_code, struct core_state *core_state)
 406 {
 407         struct task_struct *tsk = current;
 408         int core_waiters = -EBUSY;
 409
 410         init_completion(&core_state->startup);
 411         core_state->dumper.task = tsk;
 412         core_state->dumper.next = NULL;
 413
 414         core_waiters = zap_threads(tsk, core_state, exit_code);
 415         if (core_waiters > 0) {
 416                 struct core_thread *ptr;
 417
 418                 wait_for_completion_state(&core_state->startup,
 419                                           TASK_UNINTERRUPTIBLE|TASK_FREEZABLE);
 420                 /*
 421                  * Wait for all the threads to become inactive, so that
 422                  * all the thread context (extended register state, like
 423                  * fpu etc) gets copied to the memory.
 424                  */
 425                 ptr = core_state->dumper.next;
 426                 while (ptr != NULL) {
 427                         wait_task_inactive(ptr->task, TASK_ANY);
 428                         ptr = ptr->next;
 429                 }
 430         }
 431
 432         return core_waiters;
 433 }
 434
 435 static void coredump_finish(bool core_dumped)
 436 {
 437         struct core_thread *curr, *next;
 438         struct task_struct *task;
 439
 440         spin_lock_irq(&current->sighand->siglock);
 441         if (core_dumped && !__fatal_signal_pending(current))
 442                 current->signal->group_exit_code |= 0x80;
 443         next = current->signal->core_state->dumper.next;
 444         current->signal->core_state = NULL;
 445         spin_unlock_irq(&current->sighand->siglock);
 446
 447         while ((curr = next) != NULL) {
 448                 next = curr->next;
 449                 task = curr->task;
 450                 /*
 451                  * see coredump_task_exit(), curr->task must not see
 452                  * ->task == NULL before we read ->next.
 453                  */
 454                 smp_mb();
 455                 curr->task = NULL;
 456                 wake_up_process(task);
 457         }
 458 }
 459
 460 static bool dump_interrupted(void)
 461 {
 462         /*
 463          * SIGKILL or freezing() interrupt the coredumping. Perhaps we
 464          * can do try_to_freeze() and check __fatal_signal_pending(),
 465          * but then we need to teach dump_write() to restart and clear
 466          * TIF_SIGPENDING.
 467          */
 468         return fatal_signal_pending(current) || freezing(current);
 469 }
 470
 471 static void wait_for_dump_helpers(struct file *file)
 472 {
 473         struct pipe_inode_info *pipe = file->private_data;
 474
 475         pipe_lock(pipe);
 476         pipe->readers++;
 477         pipe->writers--;
 478         wake_up_interruptible_sync(&pipe->rd_wait);
 479         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 480         pipe_unlock(pipe);
 481
 482         /*
 483          * We actually want wait_event_freezable() but then we need
 484          * to clear TIF_SIGPENDING and improve dump_interrupted().
 485          */
 486         wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
 487
 488         pipe_lock(pipe);
 489         pipe->readers--;
 490         pipe->writers++;
 491         pipe_unlock(pipe);
 492 }
 493
 494 /*
 495  * umh_pipe_setup
 496  * helper function to customize the process used
 497  * to collect the core in userspace.  Specifically
 498  * it sets up a pipe and installs it as fd 0 (stdin)
 499  * for the process.  Returns 0 on success, or
 500  * PTR_ERR on failure.
 501  * Note that it also sets the core limit to 1.  This
 502  * is a special value that we use to trap recursive
 503  * core dumps
 504  */
 505 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
 506 {
 507         struct file *files[2];
 508         struct coredump_params *cp = (struct coredump_params *)info->data;
 509         int err = create_pipe_files(files, 0);
 510         if (err)
 511                 return err;
 512
 513         cp->file = files[1];
 514
 515         err = replace_fd(0, files[0], 0);
 516         fput(files[0]);
 517         /* and disallow core files too */
 518         current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
 519
 520         return err;
 521 }
 522
 523 void do_coredump(const kernel_siginfo_t *siginfo)
 524 {
 525         struct core_state core_state;
 526         struct core_name cn;
 527         struct mm_struct *mm = current->mm;
 528         struct linux_binfmt * binfmt;
 529         const struct cred *old_cred;
 530         struct cred *cred;
 531         int retval = 0;
 532         int ispipe;
 533         size_t *argv = NULL;
 534         int argc = 0;
 535         /* require nonrelative corefile path and be extra careful */
 536         bool need_suid_safe = false;
 537         bool core_dumped = false;
 538         static atomic_t core_dump_count = ATOMIC_INIT(0);
 539         struct coredump_params cprm = {
 540                 .siginfo = siginfo,
 541                 .limit = rlimit(RLIMIT_CORE),
 542                 /*
 543                  * We must use the same mm->flags while dumping core to avoid
 544                  * inconsistency of bit flags, since this flag is not protected
 545                  * by any locks.
 546                  */
 547                 .mm_flags = mm->flags,
 548                 .vma_meta = NULL,
 549                 .cpu = raw_smp_processor_id(),
 550         };
 551
 552         audit_core_dumps(siginfo->si_signo);
 553
 554         binfmt = mm->binfmt;
 555         if (!binfmt || !binfmt->core_dump)
 556                 goto fail;
 557         if (!__get_dumpable(cprm.mm_flags))
 558                 goto fail;
 559
 560         cred = prepare_creds();
 561         if (!cred)
 562                 goto fail;
 563         /*
 564          * We cannot trust fsuid as being the "true" uid of the process
 565          * nor do we know its entire history. We only know it was tainted
 566          * so we dump it as root in mode 2, and only into a controlled
 567          * environment (pipe handler or fully qualified path).
 568          */
 569         if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
 570                 /* Setuid core dump mode */
 571                 cred->fsuid = GLOBAL_ROOT_UID;  /* Dump root private */
 572                 need_suid_safe = true;
 573         }
 574
 575         retval = coredump_wait(siginfo->si_signo, &core_state);
 576         if (retval < 0)
 577                 goto fail_creds;
 578
 579         old_cred = override_creds(cred);
 580
 581         ispipe = format_corename(&cn, &cprm, &argv, &argc);
 582
 583         if (ispipe) {
 584                 int argi;
 585                 int dump_count;
 586                 char **helper_argv;
 587                 struct subprocess_info *sub_info;
 588
 589                 if (ispipe < 0) {
 590                         coredump_report_failure("format_corename failed, aborting core");
 591                         goto fail_unlock;
 592                 }
 593
 594                 if (cprm.limit == 1) {
 595                         /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
 596                          *
 597                          * Normally core limits are irrelevant to pipes, since
 598                          * we're not writing to the file system, but we use
 599                          * cprm.limit of 1 here as a special value, this is a
 600                          * consistent way to catch recursive crashes.
 601                          * We can still crash if the core_pattern binary sets
 602                          * RLIM_CORE = !1, but it runs as root, and can do
 603                          * lots of stupid things.
 604                          *
 605                          * Note that we use task_tgid_vnr here to grab the pid
 606                          * of the process group leader.  That way we get the
 607                          * right pid if a thread in a multi-threaded
 608                          * core_pattern process dies.
 609                          */
 610                         coredump_report_failure("RLIMIT_CORE is set to 1, aborting core");
 611                         goto fail_unlock;
 612                 }
 613                 cprm.limit = RLIM_INFINITY;
 614
 615                 dump_count = atomic_inc_return(&core_dump_count);
 616                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
 617                         coredump_report_failure("over core_pipe_limit, skipping core dump");
 618                         goto fail_dropcount;
 619                 }
 620
 621                 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
 622                                             GFP_KERNEL);
 623                 if (!helper_argv) {
 624                         coredump_report_failure("%s failed to allocate memory", __func__);
 625                         goto fail_dropcount;
 626                 }
 627                 for (argi = 0; argi < argc; argi++)
 628                         helper_argv[argi] = cn.corename + argv[argi];
 629                 helper_argv[argi] = NULL;
 630
 631                 retval = -ENOMEM;
 632                 sub_info = call_usermodehelper_setup(helper_argv[0],
 633                                                 helper_argv, NULL, GFP_KERNEL,
 634                                                 umh_pipe_setup, NULL, &cprm);
 635                 if (sub_info)
 636                         retval = call_usermodehelper_exec(sub_info,
 637                                                           UMH_WAIT_EXEC);
 638
 639                 kfree(helper_argv);
 640                 if (retval) {
 641                         coredump_report_failure("|%s pipe failed", cn.corename);
 642                         goto close_fail;
 643                 }
 644         } else {
 645                 struct mnt_idmap *idmap;
 646                 struct inode *inode;
 647                 int open_flags = O_CREAT | O_WRONLY | O_NOFOLLOW |
 648                                  O_LARGEFILE | O_EXCL;
 649
 650                 if (cprm.limit < binfmt->min_coredump)
 651                         goto fail_unlock;
 652
 653                 if (need_suid_safe && cn.corename[0] != '/') {
 654                         coredump_report_failure(
 655                                 "this process can only dump core to a fully qualified path, skipping core dump");
 656                         goto fail_unlock;
 657                 }
 658
 659                 /*
 660                  * Unlink the file if it exists unless this is a SUID
 661                  * binary - in that case, we're running around with root
 662                  * privs and don't want to unlink another user's coredump.
 663                  */
 664                 if (!need_suid_safe) {
 665                         /*
 666                          * If it doesn't exist, that's fine. If there's some
 667                          * other problem, we'll catch it at the filp_open().
 668                          */
 669                         do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
 670                 }
 671
 672                 /*
 673                  * There is a race between unlinking and creating the
 674                  * file, but if that causes an EEXIST here, that's
 675                  * fine - another process raced with us while creating
 676                  * the corefile, and the other process won. To userspace,
 677                  * what matters is that at least one of the two processes
 678                  * writes its coredump successfully, not which one.
 679                  */
 680                 if (need_suid_safe) {
 681                         /*
 682                          * Using user namespaces, normal user tasks can change
 683                          * their current->fs->root to point to arbitrary
 684                          * directories. Since the intention of the "only dump
 685                          * with a fully qualified path" rule is to control where
 686                          * coredumps may be placed using root privileges,
 687                          * current->fs->root must not be used. Instead, use the
 688                          * root directory of init_task.
 689                          */
 690                         struct path root;
 691
 692                         task_lock(&init_task);
 693                         get_fs_root(init_task.fs, &root);
 694                         task_unlock(&init_task);
 695                         cprm.file = file_open_root(&root, cn.corename,
 696                                                    open_flags, 0600);
 697                         path_put(&root);
 698                 } else {
 699                         cprm.file = filp_open(cn.corename, open_flags, 0600);
 700                 }
 701                 if (IS_ERR(cprm.file))
 702                         goto fail_unlock;
 703
 704                 inode = file_inode(cprm.file);
 705                 if (inode->i_nlink > 1)
 706                         goto close_fail;
 707                 if (d_unhashed(cprm.file->f_path.dentry))
 708                         goto close_fail;
 709                 /*
 710                  * AK: actually i see no reason to not allow this for named
 711                  * pipes etc, but keep the previous behaviour for now.
 712                  */
 713                 if (!S_ISREG(inode->i_mode))
 714                         goto close_fail;
 715                 /*
 716                  * Don't dump core if the filesystem changed owner or mode
 717                  * of the file during file creation. This is an issue when
 718                  * a process dumps core while its cwd is e.g. on a vfat
 719                  * filesystem.
 720                  */
 721                 idmap = file_mnt_idmap(cprm.file);
 722                 if (!vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode),
 723                                     current_fsuid())) {
 724                         coredump_report_failure("Core dump to %s aborted: "
 725                                 "cannot preserve file owner", cn.corename);
 726                         goto close_fail;
 727                 }
 728                 if ((inode->i_mode & 0677) != 0600) {
 729                         coredump_report_failure("Core dump to %s aborted: "
 730                                 "cannot preserve file permissions", cn.corename);
 731                         goto close_fail;
 732                 }
 733                 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
 734                         goto close_fail;
 735                 if (do_truncate(idmap, cprm.file->f_path.dentry,
 736                                 0, 0, cprm.file))
 737                         goto close_fail;
 738         }
 739
 740         /* get us an unshared descriptor table; almost always a no-op */
 741         /* The cell spufs coredump code reads the file descriptor tables */
 742         retval = unshare_files();
 743         if (retval)
 744                 goto close_fail;
 745         if (!dump_interrupted()) {
 746                 /*
 747                  * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
 748                  * have this set to NULL.
 749                  */
 750                 if (!cprm.file) {
 751                         coredump_report_failure("Core dump to |%s disabled", cn.corename);
 752                         goto close_fail;
 753                 }
 754                 if (!dump_vma_snapshot(&cprm))
 755                         goto close_fail;
 756
 757                 file_start_write(cprm.file);
 758                 core_dumped = binfmt->core_dump(&cprm);
 759                 /*
 760                  * Ensures that file size is big enough to contain the current
 761                  * file postion. This prevents gdb from complaining about
 762                  * a truncated file if the last "write" to the file was
 763                  * dump_skip.
 764                  */
 765                 if (cprm.to_skip) {
 766                         cprm.to_skip--;
 767                         dump_emit(&cprm, "", 1);
 768                 }
 769                 file_end_write(cprm.file);
 770                 free_vma_snapshot(&cprm);
 771         }
 772         if (ispipe && core_pipe_limit)
 773                 wait_for_dump_helpers(cprm.file);
 774 close_fail:
 775         if (cprm.file)
 776                 filp_close(cprm.file, NULL);
 777 fail_dropcount:
 778         if (ispipe)
 779                 atomic_dec(&core_dump_count);
 780 fail_unlock:
 781         kfree(argv);
 782         kfree(cn.corename);
 783         coredump_finish(core_dumped);
 784         revert_creds(old_cred);
 785 fail_creds:
 786         put_cred(cred);
 787 fail:
 788         return;
 789 }
 790
 791 /*
 792  * Core dumping helper functions.  These are the only things you should
 793  * do on a core-file: use only these functions to write out all the
 794  * necessary info.
 795  */
 796 static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr)
 797 {
 798         struct file *file = cprm->file;
 799         loff_t pos = file->f_pos;
 800         ssize_t n;
 801         if (cprm->written + nr > cprm->limit)
 802                 return 0;
 803
 804
 805         if (dump_interrupted())
 806                 return 0;
 807         n = __kernel_write(file, addr, nr, &pos);
 808         if (n != nr)
 809                 return 0;
 810         file->f_pos = pos;
 811         cprm->written += n;
 812         cprm->pos += n;
 813
 814         return 1;
 815 }
 816
 817 static int __dump_skip(struct coredump_params *cprm, size_t nr)
 818 {
 819         static char zeroes[PAGE_SIZE];
 820         struct file *file = cprm->file;
 821         if (file->f_mode & FMODE_LSEEK) {
 822                 if (dump_interrupted() ||
 823                     vfs_llseek(file, nr, SEEK_CUR) < 0)
 824                         return 0;
 825                 cprm->pos += nr;
 826                 return 1;
 827         } else {
 828                 while (nr > PAGE_SIZE) {
 829                         if (!__dump_emit(cprm, zeroes, PAGE_SIZE))
 830                                 return 0;
 831                         nr -= PAGE_SIZE;
 832                 }
 833                 return __dump_emit(cprm, zeroes, nr);
 834         }
 835 }
 836
 837 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
 838 {
 839         if (cprm->to_skip) {
 840                 if (!__dump_skip(cprm, cprm->to_skip))
 841                         return 0;
 842                 cprm->to_skip = 0;
 843         }
 844         return __dump_emit(cprm, addr, nr);
 845 }
 846 EXPORT_SYMBOL(dump_emit);
 847
 848 void dump_skip_to(struct coredump_params *cprm, unsigned long pos)
 849 {
 850         cprm->to_skip = pos - cprm->pos;
 851 }
 852 EXPORT_SYMBOL(dump_skip_to);
 853
 854 void dump_skip(struct coredump_params *cprm, size_t nr)
 855 {
 856         cprm->to_skip += nr;
 857 }
 858 EXPORT_SYMBOL(dump_skip);
 859
 860 #ifdef CONFIG_ELF_CORE
 861 static int dump_emit_page(struct coredump_params *cprm, struct page *page)
 862 {
 863         struct bio_vec bvec;
 864         struct iov_iter iter;
 865         struct file *file = cprm->file;
 866         loff_t pos;
 867         ssize_t n;
 868
 869         if (!page)
 870                 return 0;
 871
 872         if (cprm->to_skip) {
 873                 if (!__dump_skip(cprm, cprm->to_skip))
 874                         return 0;
 875                 cprm->to_skip = 0;
 876         }
 877         if (cprm->written + PAGE_SIZE > cprm->limit)
 878                 return 0;
 879         if (dump_interrupted())
 880                 return 0;
 881         pos = file->f_pos;
 882         bvec_set_page(&bvec, page, PAGE_SIZE, 0);
 883         iov_iter_bvec(&iter, ITER_SOURCE, &bvec, 1, PAGE_SIZE);
 884         n = __kernel_write_iter(cprm->file, &iter, &pos);
 885         if (n != PAGE_SIZE)
 886                 return 0;
 887         file->f_pos = pos;
 888         cprm->written += PAGE_SIZE;
 889         cprm->pos += PAGE_SIZE;
 890
 891         return 1;
 892 }
 893
 894 /*
 895  * If we might get machine checks from kernel accesses during the
 896  * core dump, let's get those errors early rather than during the
 897  * IO. This is not performance-critical enough to warrant having
 898  * all the machine check logic in the iovec paths.
 899  */
 900 #ifdef copy_mc_to_kernel
 901
 902 #define dump_page_alloc() alloc_page(GFP_KERNEL)
 903 #define dump_page_free(x) __free_page(x)
 904 static struct page *dump_page_copy(struct page *src, struct page *dst)
 905 {
 906         void *buf = kmap_local_page(src);
 907         size_t left = copy_mc_to_kernel(page_address(dst), buf, PAGE_SIZE);
 908         kunmap_local(buf);
 909         return left ? NULL : dst;
 910 }
 911
 912 #else
 913
 914 /* We just want to return non-NULL; it's never used. */
 915 #define dump_page_alloc() ERR_PTR(-EINVAL)
 916 #define dump_page_free(x) ((void)(x))
 917 static inline struct page *dump_page_copy(struct page *src, struct page *dst)
 918 {
 919         return src;
 920 }
 921 #endif
 922
 923 int dump_user_range(struct coredump_params *cprm, unsigned long start,
 924                     unsigned long len)
 925 {
 926         unsigned long addr;
 927         struct page *dump_page;
 928
 929         dump_page = dump_page_alloc();
 930         if (!dump_page)
 931                 return 0;
 932
 933         for (addr = start; addr < start + len; addr += PAGE_SIZE) {
 934                 struct page *page;
 935
 936                 /*
 937                  * To avoid having to allocate page tables for virtual address
 938                  * ranges that have never been used yet, and also to make it
 939                  * easy to generate sparse core files, use a helper that returns
 940                  * NULL when encountering an empty page table entry that would
 941                  * otherwise have been filled with the zero page.
 942                  */
 943                 page = get_dump_page(addr);
 944                 if (page) {
 945                         int stop = !dump_emit_page(cprm, dump_page_copy(page, dump_page));
 946                         put_page(page);
 947                         if (stop) {
 948                                 dump_page_free(dump_page);
 949                                 return 0;
 950                         }
 951                 } else {
 952                         dump_skip(cprm, PAGE_SIZE);
 953                 }
 954                 cond_resched();
 955         }
 956         dump_page_free(dump_page);
 957         return 1;
 958 }
 959 #endif
 960
 961 int dump_align(struct coredump_params *cprm, int align)
 962 {
 963         unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1);
 964         if (align & (align - 1))
 965                 return 0;
 966         if (mod)
 967                 cprm->to_skip += align - mod;
 968         return 1;
 969 }
 970 EXPORT_SYMBOL(dump_align);
 971
 972 #ifdef CONFIG_SYSCTL
 973
 974 void validate_coredump_safety(void)
 975 {
 976         if (suid_dumpable == SUID_DUMP_ROOT &&
 977             core_pattern[0] != '/' && core_pattern[0] != '|') {
 978
 979                 coredump_report_failure("Unsafe core_pattern used with fs.suid_dumpable=2: "
 980                         "pipe handler or fully qualified core dump path required. "
 981                         "Set kernel.core_pattern before fs.suid_dumpable.");
 982         }
 983 }
 984
 985 static int proc_dostring_coredump(const struct ctl_table *table, int write,
 986                   void *buffer, size_t *lenp, loff_t *ppos)
 987 {
 988         int error = proc_dostring(table, write, buffer, lenp, ppos);
 989
 990         if (!error)
 991                 validate_coredump_safety();
 992         return error;
 993 }
 994
 995 static const unsigned int core_file_note_size_min = CORE_FILE_NOTE_SIZE_DEFAULT;
 996 static const unsigned int core_file_note_size_max = CORE_FILE_NOTE_SIZE_MAX;
 997
 998 static struct ctl_table coredump_sysctls[] = {
 999         {
1000                 .procname       = "core_uses_pid",
1001                 .data           = &core_uses_pid,
1002                 .maxlen         = sizeof(int),
1003                 .mode           = 0644,
1004                 .proc_handler   = proc_dointvec,
1005         },
1006         {
1007                 .procname       = "core_pattern",
1008                 .data           = core_pattern,
1009                 .maxlen         = CORENAME_MAX_SIZE,
1010                 .mode           = 0644,
1011                 .proc_handler   = proc_dostring_coredump,
1012         },
1013         {
1014                 .procname       = "core_pipe_limit",
1015                 .data           = &core_pipe_limit,
1016                 .maxlen         = sizeof(unsigned int),
1017                 .mode           = 0644,
1018                 .proc_handler   = proc_dointvec,
1019         },
1020         {
1021                 .procname       = "core_file_note_size_limit",
1022                 .data           = &core_file_note_size_limit,
1023                 .maxlen         = sizeof(unsigned int),
1024                 .mode           = 0644,
1025                 .proc_handler   = proc_douintvec_minmax,
1026                 .extra1         = (unsigned int *)&core_file_note_size_min,
1027                 .extra2         = (unsigned int *)&core_file_note_size_max,
1028         },
1029 };
1030
1031 static int __init init_fs_coredump_sysctls(void)
1032 {
1033         register_sysctl_init("kernel", coredump_sysctls);
1034         return 0;
1035 }
1036 fs_initcall(init_fs_coredump_sysctls);
1037 #endif /* CONFIG_SYSCTL */
1038
1039 /*
1040  * The purpose of always_dump_vma() is to make sure that special kernel mappings
1041  * that are useful for post-mortem analysis are included in every core dump.
1042  * In that way we ensure that the core dump is fully interpretable later
1043  * without matching up the same kernel and hardware config to see what PC values
1044  * meant. These special mappings include - vDSO, vsyscall, and other
1045  * architecture specific mappings
1046  */
1047 static bool always_dump_vma(struct vm_area_struct *vma)
1048 {
1049         /* Any vsyscall mappings? */
1050         if (vma == get_gate_vma(vma->vm_mm))
1051                 return true;
1052
1053         /*
1054          * Assume that all vmas with a .name op should always be dumped.
1055          * If this changes, a new vm_ops field can easily be added.
1056          */
1057         if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
1058                 return true;
1059
1060         /*
1061          * arch_vma_name() returns non-NULL for special architecture mappings,
1062          * such as vDSO sections.
1063          */
1064         if (arch_vma_name(vma))
1065                 return true;
1066
1067         return false;
1068 }
1069
1070 #define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1
1071
1072 /*
1073  * Decide how much of @vma's contents should be included in a core dump.
1074  */
1075 static unsigned long vma_dump_size(struct vm_area_struct *vma,
1076                                    unsigned long mm_flags)
1077 {
1078 #define FILTER(type)    (mm_flags & (1UL << MMF_DUMP_##type))
1079
1080         /* always dump the vdso and vsyscall sections */
1081         if (always_dump_vma(vma))
1082                 goto whole;
1083
1084         if (vma->vm_flags & VM_DONTDUMP)
1085                 return 0;
1086
1087         /* support for DAX */
1088         if (vma_is_dax(vma)) {
1089                 if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
1090                         goto whole;
1091                 if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
1092                         goto whole;
1093                 return 0;
1094         }
1095
1096         /* Hugetlb memory check */
1097         if (is_vm_hugetlb_page(vma)) {
1098                 if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
1099                         goto whole;
1100                 if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
1101                         goto whole;
1102                 return 0;
1103         }
1104
1105         /* Do not dump I/O mapped devices or special mappings */
1106         if (vma->vm_flags & VM_IO)
1107                 return 0;
1108
1109         /* By default, dump shared memory if mapped from an anonymous file. */
1110         if (vma->vm_flags & VM_SHARED) {
1111                 if (file_inode(vma->vm_file)->i_nlink == 0 ?
1112                     FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
1113                         goto whole;
1114                 return 0;
1115         }
1116
1117         /* Dump segments that have been written to.  */
1118         if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
1119                 goto whole;
1120         if (vma->vm_file == NULL)
1121                 return 0;
1122
1123         if (FILTER(MAPPED_PRIVATE))
1124                 goto whole;
1125
1126         /*
1127          * If this is the beginning of an executable file mapping,
1128          * dump the first page to aid in determining what was mapped here.
1129          */
1130         if (FILTER(ELF_HEADERS) &&
1131             vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
1132                 if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
1133                         return PAGE_SIZE;
1134
1135                 /*
1136                  * ELF libraries aren't always executable.
1137                  * We'll want to check whether the mapping starts with the ELF
1138                  * magic, but not now - we're holding the mmap lock,
1139                  * so copy_from_user() doesn't work here.
1140                  * Use a placeholder instead, and fix it up later in
1141                  * dump_vma_snapshot().
1142                  */
1143                 return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER;
1144         }
1145
1146 #undef  FILTER
1147
1148         return 0;
1149
1150 whole:
1151         return vma->vm_end - vma->vm_start;
1152 }
1153
1154 /*
1155  * Helper function for iterating across a vma list.  It ensures that the caller
1156  * will visit `gate_vma' prior to terminating the search.
1157  */
1158 static struct vm_area_struct *coredump_next_vma(struct vma_iterator *vmi,
1159                                        struct vm_area_struct *vma,
1160                                        struct vm_area_struct *gate_vma)
1161 {
1162         if (gate_vma && (vma == gate_vma))
1163                 return NULL;
1164
1165         vma = vma_next(vmi);
1166         if (vma)
1167                 return vma;
1168         return gate_vma;
1169 }
1170
1171 static void free_vma_snapshot(struct coredump_params *cprm)
1172 {
1173         if (cprm->vma_meta) {
1174                 int i;
1175                 for (i = 0; i < cprm->vma_count; i++) {
1176                         struct file *file = cprm->vma_meta[i].file;
1177                         if (file)
1178                                 fput(file);
1179                 }
1180                 kvfree(cprm->vma_meta);
1181                 cprm->vma_meta = NULL;
1182         }
1183 }
1184
1185 static int cmp_vma_size(const void *vma_meta_lhs_ptr, const void *vma_meta_rhs_ptr)
1186 {
1187         const struct core_vma_metadata *vma_meta_lhs = vma_meta_lhs_ptr;
1188         const struct core_vma_metadata *vma_meta_rhs = vma_meta_rhs_ptr;
1189
1190         if (vma_meta_lhs->dump_size < vma_meta_rhs->dump_size)
1191                 return -1;
1192         if (vma_meta_lhs->dump_size > vma_meta_rhs->dump_size)
1193                 return 1;
1194         return 0;
1195 }
1196
1197 /*
1198  * Under the mmap_lock, take a snapshot of relevant information about the task's
1199  * VMAs.
1200  */
1201 static bool dump_vma_snapshot(struct coredump_params *cprm)
1202 {
1203         struct vm_area_struct *gate_vma, *vma = NULL;
1204         struct mm_struct *mm = current->mm;
1205         VMA_ITERATOR(vmi, mm, 0);
1206         int i = 0;
1207
1208         /*
1209          * Once the stack expansion code is fixed to not change VMA bounds
1210          * under mmap_lock in read mode, this can be changed to take the
1211          * mmap_lock in read mode.
1212          */
1213         if (mmap_write_lock_killable(mm))
1214                 return false;
1215
1216         cprm->vma_data_size = 0;
1217         gate_vma = get_gate_vma(mm);
1218         cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0);
1219
1220         cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL);
1221         if (!cprm->vma_meta) {
1222                 mmap_write_unlock(mm);
1223                 return false;
1224         }
1225
1226         while ((vma = coredump_next_vma(&vmi, vma, gate_vma)) != NULL) {
1227                 struct core_vma_metadata *m = cprm->vma_meta + i;
1228
1229                 m->start = vma->vm_start;
1230                 m->end = vma->vm_end;
1231                 m->flags = vma->vm_flags;
1232                 m->dump_size = vma_dump_size(vma, cprm->mm_flags);
1233                 m->pgoff = vma->vm_pgoff;
1234                 m->file = vma->vm_file;
1235                 if (m->file)
1236                         get_file(m->file);
1237                 i++;
1238         }
1239
1240         mmap_write_unlock(mm);
1241
1242         for (i = 0; i < cprm->vma_count; i++) {
1243                 struct core_vma_metadata *m = cprm->vma_meta + i;
1244
1245                 if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) {
1246                         char elfmag[SELFMAG];
1247
1248                         if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) ||
1249                                         memcmp(elfmag, ELFMAG, SELFMAG) != 0) {
1250                                 m->dump_size = 0;
1251                         } else {
1252                                 m->dump_size = PAGE_SIZE;
1253                         }
1254                 }
1255
1256                 cprm->vma_data_size += m->dump_size;
1257         }
1258
1259         sort(cprm->vma_meta, cprm->vma_count, sizeof(*cprm->vma_meta),
1260                 cmp_vma_size, NULL);
1261
1262         return true;
1263 }