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