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