1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/slab.h> 3 #include <linux/file.h> 4 #include <linux/fdtable.h> 5 #include <linux/freezer.h> 6 #include <linux/mm.h> 7 #include <linux/stat.h> 8 #include <linux/fcntl.h> 9 #include <linux/swap.h> 10 #include <linux/ctype.h> 11 #include <linux/string.h> 12 #include <linux/init.h> 13 #include <linux/pagemap.h> 14 #include <linux/perf_event.h> 15 #include <linux/highmem.h> 16 #include <linux/spinlock.h> 17 #include <linux/key.h> 18 #include <linux/personality.h> 19 #include <linux/binfmts.h> 20 #include <linux/coredump.h> 21 #include <linux/sched/coredump.h> 22 #include <linux/sched/signal.h> 23 #include <linux/sched/task_stack.h> 24 #include <linux/utsname.h> 25 #include <linux/pid_namespace.h> 26 #include <linux/module.h> 27 #include <linux/namei.h> 28 #include <linux/mount.h> 29 #include <linux/security.h> 30 #include <linux/syscalls.h> 31 #include <linux/tsacct_kern.h> 32 #include <linux/cn_proc.h> 33 #include <linux/audit.h> 34 #include <linux/kmod.h> 35 #include <linux/fsnotify.h> 36 #include <linux/fs_struct.h> 37 #include <linux/pipe_fs_i.h> 38 #include <linux/oom.h> 39 #include <linux/compat.h> 40 #include <linux/fs.h> 41 #include <linux/path.h> 42 #include <linux/timekeeping.h> 43 #include <linux/sysctl.h> 44 #include <linux/elf.h> 45 46 #include <linux/uaccess.h> 47 #include <asm/mmu_context.h> 48 #include <asm/tlb.h> 49 #include <asm/exec.h> 50 51 #include <trace/events/task.h> 52 #include "internal.h" 53 54 #include <trace/events/sched.h> 55 56 static bool dump_vma_snapshot(struct coredump_params *cprm); 57 static void free_vma_snapshot(struct coredump_params *cprm); 58 59 static int core_uses_pid; 60 static unsigned int core_pipe_limit; 61 static char core_pattern[CORENAME_MAX_SIZE] = "core"; 62 static int core_name_size = CORENAME_MAX_SIZE; 63 64 struct core_name { 65 char *corename; 66 int used, size; 67 }; 68 69 static int expand_corename(struct core_name *cn, int size) 70 { 71 char *corename = krealloc(cn->corename, size, GFP_KERNEL); 72 73 if (!corename) 74 return -ENOMEM; 75 76 if (size > core_name_size) /* racy but harmless */ 77 core_name_size = size; 78 79 cn->size = ksize(corename); 80 cn->corename = corename; 81 return 0; 82 } 83 84 static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt, 85 va_list arg) 86 { 87 int free, need; 88 va_list arg_copy; 89 90 again: 91 free = cn->size - cn->used; 92 93 va_copy(arg_copy, arg); 94 need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy); 95 va_end(arg_copy); 96 97 if (need < free) { 98 cn->used += need; 99 return 0; 100 } 101 102 if (!expand_corename(cn, cn->size + need - free + 1)) 103 goto again; 104 105 return -ENOMEM; 106 } 107 108 static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...) 109 { 110 va_list arg; 111 int ret; 112 113 va_start(arg, fmt); 114 ret = cn_vprintf(cn, fmt, arg); 115 va_end(arg); 116 117 return ret; 118 } 119 120 static __printf(2, 3) 121 int cn_esc_printf(struct core_name *cn, const char *fmt, ...) 122 { 123 int cur = cn->used; 124 va_list arg; 125 int ret; 126 127 va_start(arg, fmt); 128 ret = cn_vprintf(cn, fmt, arg); 129 va_end(arg); 130 131 if (ret == 0) { 132 /* 133 * Ensure that this coredump name component can't cause the 134 * resulting corefile path to consist of a ".." or ".". 135 */ 136 if ((cn->used - cur == 1 && cn->corename[cur] == '.') || 137 (cn->used - cur == 2 && cn->corename[cur] == '.' 138 && cn->corename[cur+1] == '.')) 139 cn->corename[cur] = '!'; 140 141 /* 142 * Empty names are fishy and could be used to create a "//" in a 143 * corefile name, causing the coredump to happen one directory 144 * level too high. Enforce that all components of the core 145 * pattern are at least one character long. 146 */ 147 if (cn->used == cur) 148 ret = cn_printf(cn, "!"); 149 } 150 151 for (; cur < cn->used; ++cur) { 152 if (cn->corename[cur] == '/') 153 cn->corename[cur] = '!'; 154 } 155 return ret; 156 } 157 158 static int cn_print_exe_file(struct core_name *cn, bool name_only) 159 { 160 struct file *exe_file; 161 char *pathbuf, *path, *ptr; 162 int ret; 163 164 exe_file = get_mm_exe_file(current->mm); 165 if (!exe_file) 166 return cn_esc_printf(cn, "%s (path unknown)", current->comm); 167 168 pathbuf = kmalloc(PATH_MAX, GFP_KERNEL); 169 if (!pathbuf) { 170 ret = -ENOMEM; 171 goto put_exe_file; 172 } 173 174 path = file_path(exe_file, pathbuf, PATH_MAX); 175 if (IS_ERR(path)) { 176 ret = PTR_ERR(path); 177 goto free_buf; 178 } 179 180 if (name_only) { 181 ptr = strrchr(path, '/'); 182 if (ptr) 183 path = ptr + 1; 184 } 185 ret = cn_esc_printf(cn, "%s", path); 186 187 free_buf: 188 kfree(pathbuf); 189 put_exe_file: 190 fput(exe_file); 191 return ret; 192 } 193 194 /* format_corename will inspect the pattern parameter, and output a 195 * name into corename, which must have space for at least 196 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator. 197 */ 198 static int format_corename(struct core_name *cn, struct coredump_params *cprm, 199 size_t **argv, int *argc) 200 { 201 const struct cred *cred = current_cred(); 202 const char *pat_ptr = core_pattern; 203 int ispipe = (*pat_ptr == '|'); 204 bool was_space = false; 205 int pid_in_pattern = 0; 206 int err = 0; 207 208 cn->used = 0; 209 cn->corename = NULL; 210 if (expand_corename(cn, core_name_size)) 211 return -ENOMEM; 212 cn->corename[0] = '\0'; 213 214 if (ispipe) { 215 int argvs = sizeof(core_pattern) / 2; 216 (*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL); 217 if (!(*argv)) 218 return -ENOMEM; 219 (*argv)[(*argc)++] = 0; 220 ++pat_ptr; 221 if (!(*pat_ptr)) 222 return -ENOMEM; 223 } 224 225 /* Repeat as long as we have more pattern to process and more output 226 space */ 227 while (*pat_ptr) { 228 /* 229 * Split on spaces before doing template expansion so that 230 * %e and %E don't get split if they have spaces in them 231 */ 232 if (ispipe) { 233 if (isspace(*pat_ptr)) { 234 if (cn->used != 0) 235 was_space = true; 236 pat_ptr++; 237 continue; 238 } else if (was_space) { 239 was_space = false; 240 err = cn_printf(cn, "%c", '\0'); 241 if (err) 242 return err; 243 (*argv)[(*argc)++] = cn->used; 244 } 245 } 246 if (*pat_ptr != '%') { 247 err = cn_printf(cn, "%c", *pat_ptr++); 248 } else { 249 switch (*++pat_ptr) { 250 /* single % at the end, drop that */ 251 case 0: 252 goto out; 253 /* Double percent, output one percent */ 254 case '%': 255 err = cn_printf(cn, "%c", '%'); 256 break; 257 /* pid */ 258 case 'p': 259 pid_in_pattern = 1; 260 err = cn_printf(cn, "%d", 261 task_tgid_vnr(current)); 262 break; 263 /* global pid */ 264 case 'P': 265 err = cn_printf(cn, "%d", 266 task_tgid_nr(current)); 267 break; 268 case 'i': 269 err = cn_printf(cn, "%d", 270 task_pid_vnr(current)); 271 break; 272 case 'I': 273 err = cn_printf(cn, "%d", 274 task_pid_nr(current)); 275 break; 276 /* uid */ 277 case 'u': 278 err = cn_printf(cn, "%u", 279 from_kuid(&init_user_ns, 280 cred->uid)); 281 break; 282 /* gid */ 283 case 'g': 284 err = cn_printf(cn, "%u", 285 from_kgid(&init_user_ns, 286 cred->gid)); 287 break; 288 case 'd': 289 err = cn_printf(cn, "%d", 290 __get_dumpable(cprm->mm_flags)); 291 break; 292 /* signal that caused the coredump */ 293 case 's': 294 err = cn_printf(cn, "%d", 295 cprm->siginfo->si_signo); 296 break; 297 /* UNIX time of coredump */ 298 case 't': { 299 time64_t time; 300 301 time = ktime_get_real_seconds(); 302 err = cn_printf(cn, "%lld", time); 303 break; 304 } 305 /* hostname */ 306 case 'h': 307 down_read(&uts_sem); 308 err = cn_esc_printf(cn, "%s", 309 utsname()->nodename); 310 up_read(&uts_sem); 311 break; 312 /* executable, could be changed by prctl PR_SET_NAME etc */ 313 case 'e': 314 err = cn_esc_printf(cn, "%s", current->comm); 315 break; 316 /* file name of executable */ 317 case 'f': 318 err = cn_print_exe_file(cn, true); 319 break; 320 case 'E': 321 err = cn_print_exe_file(cn, false); 322 break; 323 /* core limit size */ 324 case 'c': 325 err = cn_printf(cn, "%lu", 326 rlimit(RLIMIT_CORE)); 327 break; 328 /* CPU the task ran on */ 329 case 'C': 330 err = cn_printf(cn, "%d", cprm->cpu); 331 break; 332 default: 333 break; 334 } 335 ++pat_ptr; 336 } 337 338 if (err) 339 return err; 340 } 341 342 out: 343 /* Backward compatibility with core_uses_pid: 344 * 345 * If core_pattern does not include a %p (as is the default) 346 * and core_uses_pid is set, then .%pid will be appended to 347 * the filename. Do not do this for piped commands. */ 348 if (!ispipe && !pid_in_pattern && core_uses_pid) { 349 err = cn_printf(cn, ".%d", task_tgid_vnr(current)); 350 if (err) 351 return err; 352 } 353 return ispipe; 354 } 355 356 static int zap_process(struct task_struct *start, int exit_code) 357 { 358 struct task_struct *t; 359 int nr = 0; 360 361 /* Allow SIGKILL, see prepare_signal() */ 362 start->signal->flags = SIGNAL_GROUP_EXIT; 363 start->signal->group_exit_code = exit_code; 364 start->signal->group_stop_count = 0; 365 366 for_each_thread(start, t) { 367 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK); 368 if (t != current && !(t->flags & PF_POSTCOREDUMP)) { 369 sigaddset(&t->pending.signal, SIGKILL); 370 signal_wake_up(t, 1); 371 nr++; 372 } 373 } 374 375 return nr; 376 } 377 378 static int zap_threads(struct task_struct *tsk, 379 struct core_state *core_state, int exit_code) 380 { 381 struct signal_struct *signal = tsk->signal; 382 int nr = -EAGAIN; 383 384 spin_lock_irq(&tsk->sighand->siglock); 385 if (!(signal->flags & SIGNAL_GROUP_EXIT) && !signal->group_exec_task) { 386 signal->core_state = core_state; 387 nr = zap_process(tsk, exit_code); 388 clear_tsk_thread_flag(tsk, TIF_SIGPENDING); 389 tsk->flags |= PF_DUMPCORE; 390 atomic_set(&core_state->nr_threads, nr); 391 } 392 spin_unlock_irq(&tsk->sighand->siglock); 393 return nr; 394 } 395 396 static int coredump_wait(int exit_code, struct core_state *core_state) 397 { 398 struct task_struct *tsk = current; 399 int core_waiters = -EBUSY; 400 401 init_completion(&core_state->startup); 402 core_state->dumper.task = tsk; 403 core_state->dumper.next = NULL; 404 405 core_waiters = zap_threads(tsk, core_state, exit_code); 406 if (core_waiters > 0) { 407 struct core_thread *ptr; 408 409 wait_for_completion_state(&core_state->startup, 410 TASK_UNINTERRUPTIBLE|TASK_FREEZABLE); 411 /* 412 * Wait for all the threads to become inactive, so that 413 * all the thread context (extended register state, like 414 * fpu etc) gets copied to the memory. 415 */ 416 ptr = core_state->dumper.next; 417 while (ptr != NULL) { 418 wait_task_inactive(ptr->task, TASK_ANY); 419 ptr = ptr->next; 420 } 421 } 422 423 return core_waiters; 424 } 425 426 static void coredump_finish(bool core_dumped) 427 { 428 struct core_thread *curr, *next; 429 struct task_struct *task; 430 431 spin_lock_irq(¤t->sighand->siglock); 432 if (core_dumped && !__fatal_signal_pending(current)) 433 current->signal->group_exit_code |= 0x80; 434 next = current->signal->core_state->dumper.next; 435 current->signal->core_state = NULL; 436 spin_unlock_irq(¤t->sighand->siglock); 437 438 while ((curr = next) != NULL) { 439 next = curr->next; 440 task = curr->task; 441 /* 442 * see coredump_task_exit(), curr->task must not see 443 * ->task == NULL before we read ->next. 444 */ 445 smp_mb(); 446 curr->task = NULL; 447 wake_up_process(task); 448 } 449 } 450 451 static bool dump_interrupted(void) 452 { 453 /* 454 * SIGKILL or freezing() interrupt the coredumping. Perhaps we 455 * can do try_to_freeze() and check __fatal_signal_pending(), 456 * but then we need to teach dump_write() to restart and clear 457 * TIF_SIGPENDING. 458 */ 459 return fatal_signal_pending(current) || freezing(current); 460 } 461 462 static void wait_for_dump_helpers(struct file *file) 463 { 464 struct pipe_inode_info *pipe = file->private_data; 465 466 pipe_lock(pipe); 467 pipe->readers++; 468 pipe->writers--; 469 wake_up_interruptible_sync(&pipe->rd_wait); 470 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 471 pipe_unlock(pipe); 472 473 /* 474 * We actually want wait_event_freezable() but then we need 475 * to clear TIF_SIGPENDING and improve dump_interrupted(). 476 */ 477 wait_event_interruptible(pipe->rd_wait, pipe->readers == 1); 478 479 pipe_lock(pipe); 480 pipe->readers--; 481 pipe->writers++; 482 pipe_unlock(pipe); 483 } 484 485 /* 486 * umh_pipe_setup 487 * helper function to customize the process used 488 * to collect the core in userspace. Specifically 489 * it sets up a pipe and installs it as fd 0 (stdin) 490 * for the process. Returns 0 on success, or 491 * PTR_ERR on failure. 492 * Note that it also sets the core limit to 1. This 493 * is a special value that we use to trap recursive 494 * core dumps 495 */ 496 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new) 497 { 498 struct file *files[2]; 499 struct coredump_params *cp = (struct coredump_params *)info->data; 500 int err = create_pipe_files(files, 0); 501 if (err) 502 return err; 503 504 cp->file = files[1]; 505 506 err = replace_fd(0, files[0], 0); 507 fput(files[0]); 508 /* and disallow core files too */ 509 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1}; 510 511 return err; 512 } 513 514 void do_coredump(const kernel_siginfo_t *siginfo) 515 { 516 struct core_state core_state; 517 struct core_name cn; 518 struct mm_struct *mm = current->mm; 519 struct linux_binfmt * binfmt; 520 const struct cred *old_cred; 521 struct cred *cred; 522 int retval = 0; 523 int ispipe; 524 size_t *argv = NULL; 525 int argc = 0; 526 /* require nonrelative corefile path and be extra careful */ 527 bool need_suid_safe = false; 528 bool core_dumped = false; 529 static atomic_t core_dump_count = ATOMIC_INIT(0); 530 struct coredump_params cprm = { 531 .siginfo = siginfo, 532 .regs = signal_pt_regs(), 533 .limit = rlimit(RLIMIT_CORE), 534 /* 535 * We must use the same mm->flags while dumping core to avoid 536 * inconsistency of bit flags, since this flag is not protected 537 * by any locks. 538 */ 539 .mm_flags = mm->flags, 540 .vma_meta = NULL, 541 .cpu = raw_smp_processor_id(), 542 }; 543 544 audit_core_dumps(siginfo->si_signo); 545 546 binfmt = mm->binfmt; 547 if (!binfmt || !binfmt->core_dump) 548 goto fail; 549 if (!__get_dumpable(cprm.mm_flags)) 550 goto fail; 551 552 cred = prepare_creds(); 553 if (!cred) 554 goto fail; 555 /* 556 * We cannot trust fsuid as being the "true" uid of the process 557 * nor do we know its entire history. We only know it was tainted 558 * so we dump it as root in mode 2, and only into a controlled 559 * environment (pipe handler or fully qualified path). 560 */ 561 if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) { 562 /* Setuid core dump mode */ 563 cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */ 564 need_suid_safe = true; 565 } 566 567 retval = coredump_wait(siginfo->si_signo, &core_state); 568 if (retval < 0) 569 goto fail_creds; 570 571 old_cred = override_creds(cred); 572 573 ispipe = format_corename(&cn, &cprm, &argv, &argc); 574 575 if (ispipe) { 576 int argi; 577 int dump_count; 578 char **helper_argv; 579 struct subprocess_info *sub_info; 580 581 if (ispipe < 0) { 582 printk(KERN_WARNING "format_corename failed\n"); 583 printk(KERN_WARNING "Aborting core\n"); 584 goto fail_unlock; 585 } 586 587 if (cprm.limit == 1) { 588 /* See umh_pipe_setup() which sets RLIMIT_CORE = 1. 589 * 590 * Normally core limits are irrelevant to pipes, since 591 * we're not writing to the file system, but we use 592 * cprm.limit of 1 here as a special value, this is a 593 * consistent way to catch recursive crashes. 594 * We can still crash if the core_pattern binary sets 595 * RLIM_CORE = !1, but it runs as root, and can do 596 * lots of stupid things. 597 * 598 * Note that we use task_tgid_vnr here to grab the pid 599 * of the process group leader. That way we get the 600 * right pid if a thread in a multi-threaded 601 * core_pattern process dies. 602 */ 603 printk(KERN_WARNING 604 "Process %d(%s) has RLIMIT_CORE set to 1\n", 605 task_tgid_vnr(current), current->comm); 606 printk(KERN_WARNING "Aborting core\n"); 607 goto fail_unlock; 608 } 609 cprm.limit = RLIM_INFINITY; 610 611 dump_count = atomic_inc_return(&core_dump_count); 612 if (core_pipe_limit && (core_pipe_limit < dump_count)) { 613 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n", 614 task_tgid_vnr(current), current->comm); 615 printk(KERN_WARNING "Skipping core dump\n"); 616 goto fail_dropcount; 617 } 618 619 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv), 620 GFP_KERNEL); 621 if (!helper_argv) { 622 printk(KERN_WARNING "%s failed to allocate memory\n", 623 __func__); 624 goto fail_dropcount; 625 } 626 for (argi = 0; argi < argc; argi++) 627 helper_argv[argi] = cn.corename + argv[argi]; 628 helper_argv[argi] = NULL; 629 630 retval = -ENOMEM; 631 sub_info = call_usermodehelper_setup(helper_argv[0], 632 helper_argv, NULL, GFP_KERNEL, 633 umh_pipe_setup, NULL, &cprm); 634 if (sub_info) 635 retval = call_usermodehelper_exec(sub_info, 636 UMH_WAIT_EXEC); 637 638 kfree(helper_argv); 639 if (retval) { 640 printk(KERN_INFO "Core dump to |%s pipe failed\n", 641 cn.corename); 642 goto close_fail; 643 } 644 } else { 645 struct user_namespace *mnt_userns; 646 struct inode *inode; 647 int open_flags = O_CREAT | O_RDWR | 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 printk(KERN_WARNING "Pid %d(%s) can only dump core "\ 655 "to fully qualified path!\n", 656 task_tgid_vnr(current), current->comm); 657 printk(KERN_WARNING "Skipping core dump\n"); 658 goto fail_unlock; 659 } 660 661 /* 662 * Unlink the file if it exists unless this is a SUID 663 * binary - in that case, we're running around with root 664 * privs and don't want to unlink another user's coredump. 665 */ 666 if (!need_suid_safe) { 667 /* 668 * If it doesn't exist, that's fine. If there's some 669 * other problem, we'll catch it at the filp_open(). 670 */ 671 do_unlinkat(AT_FDCWD, getname_kernel(cn.corename)); 672 } 673 674 /* 675 * There is a race between unlinking and creating the 676 * file, but if that causes an EEXIST here, that's 677 * fine - another process raced with us while creating 678 * the corefile, and the other process won. To userspace, 679 * what matters is that at least one of the two processes 680 * writes its coredump successfully, not which one. 681 */ 682 if (need_suid_safe) { 683 /* 684 * Using user namespaces, normal user tasks can change 685 * their current->fs->root to point to arbitrary 686 * directories. Since the intention of the "only dump 687 * with a fully qualified path" rule is to control where 688 * coredumps may be placed using root privileges, 689 * current->fs->root must not be used. Instead, use the 690 * root directory of init_task. 691 */ 692 struct path root; 693 694 task_lock(&init_task); 695 get_fs_root(init_task.fs, &root); 696 task_unlock(&init_task); 697 cprm.file = file_open_root(&root, cn.corename, 698 open_flags, 0600); 699 path_put(&root); 700 } else { 701 cprm.file = filp_open(cn.corename, open_flags, 0600); 702 } 703 if (IS_ERR(cprm.file)) 704 goto fail_unlock; 705 706 inode = file_inode(cprm.file); 707 if (inode->i_nlink > 1) 708 goto close_fail; 709 if (d_unhashed(cprm.file->f_path.dentry)) 710 goto close_fail; 711 /* 712 * AK: actually i see no reason to not allow this for named 713 * pipes etc, but keep the previous behaviour for now. 714 */ 715 if (!S_ISREG(inode->i_mode)) 716 goto close_fail; 717 /* 718 * Don't dump core if the filesystem changed owner or mode 719 * of the file during file creation. This is an issue when 720 * a process dumps core while its cwd is e.g. on a vfat 721 * filesystem. 722 */ 723 mnt_userns = file_mnt_user_ns(cprm.file); 724 if (!uid_eq(i_uid_into_mnt(mnt_userns, inode), 725 current_fsuid())) { 726 pr_info_ratelimited("Core dump to %s aborted: cannot preserve file owner\n", 727 cn.corename); 728 goto close_fail; 729 } 730 if ((inode->i_mode & 0677) != 0600) { 731 pr_info_ratelimited("Core dump to %s aborted: cannot preserve file permissions\n", 732 cn.corename); 733 goto close_fail; 734 } 735 if (!(cprm.file->f_mode & FMODE_CAN_WRITE)) 736 goto close_fail; 737 if (do_truncate(mnt_userns, cprm.file->f_path.dentry, 738 0, 0, cprm.file)) 739 goto close_fail; 740 } 741 742 /* get us an unshared descriptor table; almost always a no-op */ 743 /* The cell spufs coredump code reads the file descriptor tables */ 744 retval = unshare_files(); 745 if (retval) 746 goto close_fail; 747 if (!dump_interrupted()) { 748 /* 749 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would 750 * have this set to NULL. 751 */ 752 if (!cprm.file) { 753 pr_info("Core dump to |%s disabled\n", cn.corename); 754 goto close_fail; 755 } 756 if (!dump_vma_snapshot(&cprm)) 757 goto close_fail; 758 759 file_start_write(cprm.file); 760 core_dumped = binfmt->core_dump(&cprm); 761 /* 762 * Ensures that file size is big enough to contain the current 763 * file postion. This prevents gdb from complaining about 764 * a truncated file if the last "write" to the file was 765 * dump_skip. 766 */ 767 if (cprm.to_skip) { 768 cprm.to_skip--; 769 dump_emit(&cprm, "", 1); 770 } 771 file_end_write(cprm.file); 772 free_vma_snapshot(&cprm); 773 } 774 if (ispipe && core_pipe_limit) 775 wait_for_dump_helpers(cprm.file); 776 close_fail: 777 if (cprm.file) 778 filp_close(cprm.file, NULL); 779 fail_dropcount: 780 if (ispipe) 781 atomic_dec(&core_dump_count); 782 fail_unlock: 783 kfree(argv); 784 kfree(cn.corename); 785 coredump_finish(core_dumped); 786 revert_creds(old_cred); 787 fail_creds: 788 put_cred(cred); 789 fail: 790 return; 791 } 792 793 /* 794 * Core dumping helper functions. These are the only things you should 795 * do on a core-file: use only these functions to write out all the 796 * necessary info. 797 */ 798 static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr) 799 { 800 struct file *file = cprm->file; 801 loff_t pos = file->f_pos; 802 ssize_t n; 803 if (cprm->written + nr > cprm->limit) 804 return 0; 805 806 807 if (dump_interrupted()) 808 return 0; 809 n = __kernel_write(file, addr, nr, &pos); 810 if (n != nr) 811 return 0; 812 file->f_pos = pos; 813 cprm->written += n; 814 cprm->pos += n; 815 816 return 1; 817 } 818 819 static int __dump_skip(struct coredump_params *cprm, size_t nr) 820 { 821 static char zeroes[PAGE_SIZE]; 822 struct file *file = cprm->file; 823 if (file->f_mode & FMODE_LSEEK) { 824 if (dump_interrupted() || 825 vfs_llseek(file, nr, SEEK_CUR) < 0) 826 return 0; 827 cprm->pos += nr; 828 return 1; 829 } else { 830 while (nr > PAGE_SIZE) { 831 if (!__dump_emit(cprm, zeroes, PAGE_SIZE)) 832 return 0; 833 nr -= PAGE_SIZE; 834 } 835 return __dump_emit(cprm, zeroes, nr); 836 } 837 } 838 839 static int dump_emit_page(struct coredump_params *cprm, struct page *page) 840 { 841 struct bio_vec bvec = { 842 .bv_page = page, 843 .bv_offset = 0, 844 .bv_len = PAGE_SIZE, 845 }; 846 struct iov_iter iter; 847 struct file *file = cprm->file; 848 loff_t pos; 849 ssize_t n; 850 851 if (cprm->to_skip) { 852 if (!__dump_skip(cprm, cprm->to_skip)) 853 return 0; 854 cprm->to_skip = 0; 855 } 856 if (cprm->written + PAGE_SIZE > cprm->limit) 857 return 0; 858 if (dump_interrupted()) 859 return 0; 860 pos = file->f_pos; 861 iov_iter_bvec(&iter, WRITE, &bvec, 1, PAGE_SIZE); 862 n = __kernel_write_iter(cprm->file, &iter, &pos); 863 if (n != PAGE_SIZE) 864 return 0; 865 file->f_pos = pos; 866 cprm->written += PAGE_SIZE; 867 cprm->pos += PAGE_SIZE; 868 869 return 1; 870 } 871 872 int dump_emit(struct coredump_params *cprm, const void *addr, int nr) 873 { 874 if (cprm->to_skip) { 875 if (!__dump_skip(cprm, cprm->to_skip)) 876 return 0; 877 cprm->to_skip = 0; 878 } 879 return __dump_emit(cprm, addr, nr); 880 } 881 EXPORT_SYMBOL(dump_emit); 882 883 void dump_skip_to(struct coredump_params *cprm, unsigned long pos) 884 { 885 cprm->to_skip = pos - cprm->pos; 886 } 887 EXPORT_SYMBOL(dump_skip_to); 888 889 void dump_skip(struct coredump_params *cprm, size_t nr) 890 { 891 cprm->to_skip += nr; 892 } 893 EXPORT_SYMBOL(dump_skip); 894 895 #ifdef CONFIG_ELF_CORE 896 int dump_user_range(struct coredump_params *cprm, unsigned long start, 897 unsigned long len) 898 { 899 unsigned long addr; 900 901 for (addr = start; addr < start + len; addr += PAGE_SIZE) { 902 struct page *page; 903 904 /* 905 * To avoid having to allocate page tables for virtual address 906 * ranges that have never been used yet, and also to make it 907 * easy to generate sparse core files, use a helper that returns 908 * NULL when encountering an empty page table entry that would 909 * otherwise have been filled with the zero page. 910 */ 911 page = get_dump_page(addr); 912 if (page) { 913 int stop = !dump_emit_page(cprm, page); 914 put_page(page); 915 if (stop) 916 return 0; 917 } else { 918 dump_skip(cprm, PAGE_SIZE); 919 } 920 } 921 return 1; 922 } 923 #endif 924 925 int dump_align(struct coredump_params *cprm, int align) 926 { 927 unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1); 928 if (align & (align - 1)) 929 return 0; 930 if (mod) 931 cprm->to_skip += align - mod; 932 return 1; 933 } 934 EXPORT_SYMBOL(dump_align); 935 936 #ifdef CONFIG_SYSCTL 937 938 void validate_coredump_safety(void) 939 { 940 if (suid_dumpable == SUID_DUMP_ROOT && 941 core_pattern[0] != '/' && core_pattern[0] != '|') { 942 pr_warn( 943 "Unsafe core_pattern used with fs.suid_dumpable=2.\n" 944 "Pipe handler or fully qualified core dump path required.\n" 945 "Set kernel.core_pattern before fs.suid_dumpable.\n" 946 ); 947 } 948 } 949 950 static int proc_dostring_coredump(struct ctl_table *table, int write, 951 void *buffer, size_t *lenp, loff_t *ppos) 952 { 953 int error = proc_dostring(table, write, buffer, lenp, ppos); 954 955 if (!error) 956 validate_coredump_safety(); 957 return error; 958 } 959 960 static struct ctl_table coredump_sysctls[] = { 961 { 962 .procname = "core_uses_pid", 963 .data = &core_uses_pid, 964 .maxlen = sizeof(int), 965 .mode = 0644, 966 .proc_handler = proc_dointvec, 967 }, 968 { 969 .procname = "core_pattern", 970 .data = core_pattern, 971 .maxlen = CORENAME_MAX_SIZE, 972 .mode = 0644, 973 .proc_handler = proc_dostring_coredump, 974 }, 975 { 976 .procname = "core_pipe_limit", 977 .data = &core_pipe_limit, 978 .maxlen = sizeof(unsigned int), 979 .mode = 0644, 980 .proc_handler = proc_dointvec, 981 }, 982 { } 983 }; 984 985 static int __init init_fs_coredump_sysctls(void) 986 { 987 register_sysctl_init("kernel", coredump_sysctls); 988 return 0; 989 } 990 fs_initcall(init_fs_coredump_sysctls); 991 #endif /* CONFIG_SYSCTL */ 992 993 /* 994 * The purpose of always_dump_vma() is to make sure that special kernel mappings 995 * that are useful for post-mortem analysis are included in every core dump. 996 * In that way we ensure that the core dump is fully interpretable later 997 * without matching up the same kernel and hardware config to see what PC values 998 * meant. These special mappings include - vDSO, vsyscall, and other 999 * architecture specific mappings 1000 */ 1001 static bool always_dump_vma(struct vm_area_struct *vma) 1002 { 1003 /* Any vsyscall mappings? */ 1004 if (vma == get_gate_vma(vma->vm_mm)) 1005 return true; 1006 1007 /* 1008 * Assume that all vmas with a .name op should always be dumped. 1009 * If this changes, a new vm_ops field can easily be added. 1010 */ 1011 if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma)) 1012 return true; 1013 1014 /* 1015 * arch_vma_name() returns non-NULL for special architecture mappings, 1016 * such as vDSO sections. 1017 */ 1018 if (arch_vma_name(vma)) 1019 return true; 1020 1021 return false; 1022 } 1023 1024 #define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1 1025 1026 /* 1027 * Decide how much of @vma's contents should be included in a core dump. 1028 */ 1029 static unsigned long vma_dump_size(struct vm_area_struct *vma, 1030 unsigned long mm_flags) 1031 { 1032 #define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type)) 1033 1034 /* always dump the vdso and vsyscall sections */ 1035 if (always_dump_vma(vma)) 1036 goto whole; 1037 1038 if (vma->vm_flags & VM_DONTDUMP) 1039 return 0; 1040 1041 /* support for DAX */ 1042 if (vma_is_dax(vma)) { 1043 if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED)) 1044 goto whole; 1045 if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE)) 1046 goto whole; 1047 return 0; 1048 } 1049 1050 /* Hugetlb memory check */ 1051 if (is_vm_hugetlb_page(vma)) { 1052 if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED)) 1053 goto whole; 1054 if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE)) 1055 goto whole; 1056 return 0; 1057 } 1058 1059 /* Do not dump I/O mapped devices or special mappings */ 1060 if (vma->vm_flags & VM_IO) 1061 return 0; 1062 1063 /* By default, dump shared memory if mapped from an anonymous file. */ 1064 if (vma->vm_flags & VM_SHARED) { 1065 if (file_inode(vma->vm_file)->i_nlink == 0 ? 1066 FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED)) 1067 goto whole; 1068 return 0; 1069 } 1070 1071 /* Dump segments that have been written to. */ 1072 if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE)) 1073 goto whole; 1074 if (vma->vm_file == NULL) 1075 return 0; 1076 1077 if (FILTER(MAPPED_PRIVATE)) 1078 goto whole; 1079 1080 /* 1081 * If this is the beginning of an executable file mapping, 1082 * dump the first page to aid in determining what was mapped here. 1083 */ 1084 if (FILTER(ELF_HEADERS) && 1085 vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) { 1086 if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0) 1087 return PAGE_SIZE; 1088 1089 /* 1090 * ELF libraries aren't always executable. 1091 * We'll want to check whether the mapping starts with the ELF 1092 * magic, but not now - we're holding the mmap lock, 1093 * so copy_from_user() doesn't work here. 1094 * Use a placeholder instead, and fix it up later in 1095 * dump_vma_snapshot(). 1096 */ 1097 return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER; 1098 } 1099 1100 #undef FILTER 1101 1102 return 0; 1103 1104 whole: 1105 return vma->vm_end - vma->vm_start; 1106 } 1107 1108 /* 1109 * Helper function for iterating across a vma list. It ensures that the caller 1110 * will visit `gate_vma' prior to terminating the search. 1111 */ 1112 static struct vm_area_struct *coredump_next_vma(struct ma_state *mas, 1113 struct vm_area_struct *vma, 1114 struct vm_area_struct *gate_vma) 1115 { 1116 if (gate_vma && (vma == gate_vma)) 1117 return NULL; 1118 1119 vma = mas_next(mas, ULONG_MAX); 1120 if (vma) 1121 return vma; 1122 return gate_vma; 1123 } 1124 1125 static void free_vma_snapshot(struct coredump_params *cprm) 1126 { 1127 if (cprm->vma_meta) { 1128 int i; 1129 for (i = 0; i < cprm->vma_count; i++) { 1130 struct file *file = cprm->vma_meta[i].file; 1131 if (file) 1132 fput(file); 1133 } 1134 kvfree(cprm->vma_meta); 1135 cprm->vma_meta = NULL; 1136 } 1137 } 1138 1139 /* 1140 * Under the mmap_lock, take a snapshot of relevant information about the task's 1141 * VMAs. 1142 */ 1143 static bool dump_vma_snapshot(struct coredump_params *cprm) 1144 { 1145 struct vm_area_struct *gate_vma, *vma = NULL; 1146 struct mm_struct *mm = current->mm; 1147 MA_STATE(mas, &mm->mm_mt, 0, 0); 1148 int i = 0; 1149 1150 /* 1151 * Once the stack expansion code is fixed to not change VMA bounds 1152 * under mmap_lock in read mode, this can be changed to take the 1153 * mmap_lock in read mode. 1154 */ 1155 if (mmap_write_lock_killable(mm)) 1156 return false; 1157 1158 cprm->vma_data_size = 0; 1159 gate_vma = get_gate_vma(mm); 1160 cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0); 1161 1162 cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL); 1163 if (!cprm->vma_meta) { 1164 mmap_write_unlock(mm); 1165 return false; 1166 } 1167 1168 while ((vma = coredump_next_vma(&mas, vma, gate_vma)) != NULL) { 1169 struct core_vma_metadata *m = cprm->vma_meta + i; 1170 1171 m->start = vma->vm_start; 1172 m->end = vma->vm_end; 1173 m->flags = vma->vm_flags; 1174 m->dump_size = vma_dump_size(vma, cprm->mm_flags); 1175 m->pgoff = vma->vm_pgoff; 1176 m->file = vma->vm_file; 1177 if (m->file) 1178 get_file(m->file); 1179 i++; 1180 } 1181 1182 mmap_write_unlock(mm); 1183 1184 for (i = 0; i < cprm->vma_count; i++) { 1185 struct core_vma_metadata *m = cprm->vma_meta + i; 1186 1187 if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) { 1188 char elfmag[SELFMAG]; 1189 1190 if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) || 1191 memcmp(elfmag, ELFMAG, SELFMAG) != 0) { 1192 m->dump_size = 0; 1193 } else { 1194 m->dump_size = PAGE_SIZE; 1195 } 1196 } 1197 1198 cprm->vma_data_size += m->dump_size; 1199 } 1200 1201 return true; 1202 } 1203