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 nr++; 375 } 376 } 377 378 return nr; 379 } 380 381 static int zap_threads(struct task_struct *tsk, 382 struct core_state *core_state, int exit_code) 383 { 384 struct signal_struct *signal = tsk->signal; 385 int nr = -EAGAIN; 386 387 spin_lock_irq(&tsk->sighand->siglock); 388 if (!(signal->flags & SIGNAL_GROUP_EXIT) && !signal->group_exec_task) { 389 signal->core_state = core_state; 390 nr = zap_process(tsk, exit_code); 391 clear_tsk_thread_flag(tsk, TIF_SIGPENDING); 392 tsk->flags |= PF_DUMPCORE; 393 atomic_set(&core_state->nr_threads, nr); 394 } 395 spin_unlock_irq(&tsk->sighand->siglock); 396 return nr; 397 } 398 399 static int coredump_wait(int exit_code, struct core_state *core_state) 400 { 401 struct task_struct *tsk = current; 402 int core_waiters = -EBUSY; 403 404 init_completion(&core_state->startup); 405 core_state->dumper.task = tsk; 406 core_state->dumper.next = NULL; 407 408 core_waiters = zap_threads(tsk, core_state, exit_code); 409 if (core_waiters > 0) { 410 struct core_thread *ptr; 411 412 wait_for_completion_state(&core_state->startup, 413 TASK_UNINTERRUPTIBLE|TASK_FREEZABLE); 414 /* 415 * Wait for all the threads to become inactive, so that 416 * all the thread context (extended register state, like 417 * fpu etc) gets copied to the memory. 418 */ 419 ptr = core_state->dumper.next; 420 while (ptr != NULL) { 421 wait_task_inactive(ptr->task, TASK_ANY); 422 ptr = ptr->next; 423 } 424 } 425 426 return core_waiters; 427 } 428 429 static void coredump_finish(bool core_dumped) 430 { 431 struct core_thread *curr, *next; 432 struct task_struct *task; 433 434 spin_lock_irq(¤t->sighand->siglock); 435 if (core_dumped && !__fatal_signal_pending(current)) 436 current->signal->group_exit_code |= 0x80; 437 next = current->signal->core_state->dumper.next; 438 current->signal->core_state = NULL; 439 spin_unlock_irq(¤t->sighand->siglock); 440 441 while ((curr = next) != NULL) { 442 next = curr->next; 443 task = curr->task; 444 /* 445 * see coredump_task_exit(), curr->task must not see 446 * ->task == NULL before we read ->next. 447 */ 448 smp_mb(); 449 curr->task = NULL; 450 wake_up_process(task); 451 } 452 } 453 454 static bool dump_interrupted(void) 455 { 456 /* 457 * SIGKILL or freezing() interrupt the coredumping. Perhaps we 458 * can do try_to_freeze() and check __fatal_signal_pending(), 459 * but then we need to teach dump_write() to restart and clear 460 * TIF_SIGPENDING. 461 */ 462 return fatal_signal_pending(current) || freezing(current); 463 } 464 465 static void wait_for_dump_helpers(struct file *file) 466 { 467 struct pipe_inode_info *pipe = file->private_data; 468 469 pipe_lock(pipe); 470 pipe->readers++; 471 pipe->writers--; 472 wake_up_interruptible_sync(&pipe->rd_wait); 473 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 474 pipe_unlock(pipe); 475 476 /* 477 * We actually want wait_event_freezable() but then we need 478 * to clear TIF_SIGPENDING and improve dump_interrupted(). 479 */ 480 wait_event_interruptible(pipe->rd_wait, pipe->readers == 1); 481 482 pipe_lock(pipe); 483 pipe->readers--; 484 pipe->writers++; 485 pipe_unlock(pipe); 486 } 487 488 /* 489 * umh_pipe_setup 490 * helper function to customize the process used 491 * to collect the core in userspace. Specifically 492 * it sets up a pipe and installs it as fd 0 (stdin) 493 * for the process. Returns 0 on success, or 494 * PTR_ERR on failure. 495 * Note that it also sets the core limit to 1. This 496 * is a special value that we use to trap recursive 497 * core dumps 498 */ 499 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new) 500 { 501 struct file *files[2]; 502 struct coredump_params *cp = (struct coredump_params *)info->data; 503 int err = create_pipe_files(files, 0); 504 if (err) 505 return err; 506 507 cp->file = files[1]; 508 509 err = replace_fd(0, files[0], 0); 510 fput(files[0]); 511 /* and disallow core files too */ 512 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1}; 513 514 return err; 515 } 516 517 void do_coredump(const kernel_siginfo_t *siginfo) 518 { 519 struct core_state core_state; 520 struct core_name cn; 521 struct mm_struct *mm = current->mm; 522 struct linux_binfmt * binfmt; 523 const struct cred *old_cred; 524 struct cred *cred; 525 int retval = 0; 526 int ispipe; 527 size_t *argv = NULL; 528 int argc = 0; 529 /* require nonrelative corefile path and be extra careful */ 530 bool need_suid_safe = false; 531 bool core_dumped = false; 532 static atomic_t core_dump_count = ATOMIC_INIT(0); 533 struct coredump_params cprm = { 534 .siginfo = siginfo, 535 .limit = rlimit(RLIMIT_CORE), 536 /* 537 * We must use the same mm->flags while dumping core to avoid 538 * inconsistency of bit flags, since this flag is not protected 539 * by any locks. 540 */ 541 .mm_flags = mm->flags, 542 .vma_meta = NULL, 543 .cpu = raw_smp_processor_id(), 544 }; 545 546 audit_core_dumps(siginfo->si_signo); 547 548 binfmt = mm->binfmt; 549 if (!binfmt || !binfmt->core_dump) 550 goto fail; 551 if (!__get_dumpable(cprm.mm_flags)) 552 goto fail; 553 554 cred = prepare_creds(); 555 if (!cred) 556 goto fail; 557 /* 558 * We cannot trust fsuid as being the "true" uid of the process 559 * nor do we know its entire history. We only know it was tainted 560 * so we dump it as root in mode 2, and only into a controlled 561 * environment (pipe handler or fully qualified path). 562 */ 563 if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) { 564 /* Setuid core dump mode */ 565 cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */ 566 need_suid_safe = true; 567 } 568 569 retval = coredump_wait(siginfo->si_signo, &core_state); 570 if (retval < 0) 571 goto fail_creds; 572 573 old_cred = override_creds(cred); 574 575 ispipe = format_corename(&cn, &cprm, &argv, &argc); 576 577 if (ispipe) { 578 int argi; 579 int dump_count; 580 char **helper_argv; 581 struct subprocess_info *sub_info; 582 583 if (ispipe < 0) { 584 printk(KERN_WARNING "format_corename failed\n"); 585 printk(KERN_WARNING "Aborting core\n"); 586 goto fail_unlock; 587 } 588 589 if (cprm.limit == 1) { 590 /* See umh_pipe_setup() which sets RLIMIT_CORE = 1. 591 * 592 * Normally core limits are irrelevant to pipes, since 593 * we're not writing to the file system, but we use 594 * cprm.limit of 1 here as a special value, this is a 595 * consistent way to catch recursive crashes. 596 * We can still crash if the core_pattern binary sets 597 * RLIM_CORE = !1, but it runs as root, and can do 598 * lots of stupid things. 599 * 600 * Note that we use task_tgid_vnr here to grab the pid 601 * of the process group leader. That way we get the 602 * right pid if a thread in a multi-threaded 603 * core_pattern process dies. 604 */ 605 printk(KERN_WARNING 606 "Process %d(%s) has RLIMIT_CORE set to 1\n", 607 task_tgid_vnr(current), current->comm); 608 printk(KERN_WARNING "Aborting core\n"); 609 goto fail_unlock; 610 } 611 cprm.limit = RLIM_INFINITY; 612 613 dump_count = atomic_inc_return(&core_dump_count); 614 if (core_pipe_limit && (core_pipe_limit < dump_count)) { 615 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n", 616 task_tgid_vnr(current), current->comm); 617 printk(KERN_WARNING "Skipping core dump\n"); 618 goto fail_dropcount; 619 } 620 621 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv), 622 GFP_KERNEL); 623 if (!helper_argv) { 624 printk(KERN_WARNING "%s failed to allocate memory\n", 625 __func__); 626 goto fail_dropcount; 627 } 628 for (argi = 0; argi < argc; argi++) 629 helper_argv[argi] = cn.corename + argv[argi]; 630 helper_argv[argi] = NULL; 631 632 retval = -ENOMEM; 633 sub_info = call_usermodehelper_setup(helper_argv[0], 634 helper_argv, NULL, GFP_KERNEL, 635 umh_pipe_setup, NULL, &cprm); 636 if (sub_info) 637 retval = call_usermodehelper_exec(sub_info, 638 UMH_WAIT_EXEC); 639 640 kfree(helper_argv); 641 if (retval) { 642 printk(KERN_INFO "Core dump to |%s pipe failed\n", 643 cn.corename); 644 goto close_fail; 645 } 646 } else { 647 struct mnt_idmap *idmap; 648 struct inode *inode; 649 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW | 650 O_LARGEFILE | O_EXCL; 651 652 if (cprm.limit < binfmt->min_coredump) 653 goto fail_unlock; 654 655 if (need_suid_safe && cn.corename[0] != '/') { 656 printk(KERN_WARNING "Pid %d(%s) can only dump core "\ 657 "to fully qualified path!\n", 658 task_tgid_vnr(current), current->comm); 659 printk(KERN_WARNING "Skipping core dump\n"); 660 goto fail_unlock; 661 } 662 663 /* 664 * Unlink the file if it exists unless this is a SUID 665 * binary - in that case, we're running around with root 666 * privs and don't want to unlink another user's coredump. 667 */ 668 if (!need_suid_safe) { 669 /* 670 * If it doesn't exist, that's fine. If there's some 671 * other problem, we'll catch it at the filp_open(). 672 */ 673 do_unlinkat(AT_FDCWD, getname_kernel(cn.corename)); 674 } 675 676 /* 677 * There is a race between unlinking and creating the 678 * file, but if that causes an EEXIST here, that's 679 * fine - another process raced with us while creating 680 * the corefile, and the other process won. To userspace, 681 * what matters is that at least one of the two processes 682 * writes its coredump successfully, not which one. 683 */ 684 if (need_suid_safe) { 685 /* 686 * Using user namespaces, normal user tasks can change 687 * their current->fs->root to point to arbitrary 688 * directories. Since the intention of the "only dump 689 * with a fully qualified path" rule is to control where 690 * coredumps may be placed using root privileges, 691 * current->fs->root must not be used. Instead, use the 692 * root directory of init_task. 693 */ 694 struct path root; 695 696 task_lock(&init_task); 697 get_fs_root(init_task.fs, &root); 698 task_unlock(&init_task); 699 cprm.file = file_open_root(&root, cn.corename, 700 open_flags, 0600); 701 path_put(&root); 702 } else { 703 cprm.file = filp_open(cn.corename, open_flags, 0600); 704 } 705 if (IS_ERR(cprm.file)) 706 goto fail_unlock; 707 708 inode = file_inode(cprm.file); 709 if (inode->i_nlink > 1) 710 goto close_fail; 711 if (d_unhashed(cprm.file->f_path.dentry)) 712 goto close_fail; 713 /* 714 * AK: actually i see no reason to not allow this for named 715 * pipes etc, but keep the previous behaviour for now. 716 */ 717 if (!S_ISREG(inode->i_mode)) 718 goto close_fail; 719 /* 720 * Don't dump core if the filesystem changed owner or mode 721 * of the file during file creation. This is an issue when 722 * a process dumps core while its cwd is e.g. on a vfat 723 * filesystem. 724 */ 725 idmap = file_mnt_idmap(cprm.file); 726 if (!vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), 727 current_fsuid())) { 728 pr_info_ratelimited("Core dump to %s aborted: cannot preserve file owner\n", 729 cn.corename); 730 goto close_fail; 731 } 732 if ((inode->i_mode & 0677) != 0600) { 733 pr_info_ratelimited("Core dump to %s aborted: cannot preserve file permissions\n", 734 cn.corename); 735 goto close_fail; 736 } 737 if (!(cprm.file->f_mode & FMODE_CAN_WRITE)) 738 goto close_fail; 739 if (do_truncate(idmap, cprm.file->f_path.dentry, 740 0, 0, cprm.file)) 741 goto close_fail; 742 } 743 744 /* get us an unshared descriptor table; almost always a no-op */ 745 /* The cell spufs coredump code reads the file descriptor tables */ 746 retval = unshare_files(); 747 if (retval) 748 goto close_fail; 749 if (!dump_interrupted()) { 750 /* 751 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would 752 * have this set to NULL. 753 */ 754 if (!cprm.file) { 755 pr_info("Core dump to |%s disabled\n", cn.corename); 756 goto close_fail; 757 } 758 if (!dump_vma_snapshot(&cprm)) 759 goto close_fail; 760 761 file_start_write(cprm.file); 762 core_dumped = binfmt->core_dump(&cprm); 763 /* 764 * Ensures that file size is big enough to contain the current 765 * file postion. This prevents gdb from complaining about 766 * a truncated file if the last "write" to the file was 767 * dump_skip. 768 */ 769 if (cprm.to_skip) { 770 cprm.to_skip--; 771 dump_emit(&cprm, "", 1); 772 } 773 file_end_write(cprm.file); 774 free_vma_snapshot(&cprm); 775 } 776 if (ispipe && core_pipe_limit) 777 wait_for_dump_helpers(cprm.file); 778 close_fail: 779 if (cprm.file) 780 filp_close(cprm.file, NULL); 781 fail_dropcount: 782 if (ispipe) 783 atomic_dec(&core_dump_count); 784 fail_unlock: 785 kfree(argv); 786 kfree(cn.corename); 787 coredump_finish(core_dumped); 788 revert_creds(old_cred); 789 fail_creds: 790 put_cred(cred); 791 fail: 792 return; 793 } 794 795 /* 796 * Core dumping helper functions. These are the only things you should 797 * do on a core-file: use only these functions to write out all the 798 * necessary info. 799 */ 800 static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr) 801 { 802 struct file *file = cprm->file; 803 loff_t pos = file->f_pos; 804 ssize_t n; 805 if (cprm->written + nr > cprm->limit) 806 return 0; 807 808 809 if (dump_interrupted()) 810 return 0; 811 n = __kernel_write(file, addr, nr, &pos); 812 if (n != nr) 813 return 0; 814 file->f_pos = pos; 815 cprm->written += n; 816 cprm->pos += n; 817 818 return 1; 819 } 820 821 static int __dump_skip(struct coredump_params *cprm, size_t nr) 822 { 823 static char zeroes[PAGE_SIZE]; 824 struct file *file = cprm->file; 825 if (file->f_mode & FMODE_LSEEK) { 826 if (dump_interrupted() || 827 vfs_llseek(file, nr, SEEK_CUR) < 0) 828 return 0; 829 cprm->pos += nr; 830 return 1; 831 } else { 832 while (nr > PAGE_SIZE) { 833 if (!__dump_emit(cprm, zeroes, PAGE_SIZE)) 834 return 0; 835 nr -= PAGE_SIZE; 836 } 837 return __dump_emit(cprm, zeroes, nr); 838 } 839 } 840 841 int dump_emit(struct coredump_params *cprm, const void *addr, int nr) 842 { 843 if (cprm->to_skip) { 844 if (!__dump_skip(cprm, cprm->to_skip)) 845 return 0; 846 cprm->to_skip = 0; 847 } 848 return __dump_emit(cprm, addr, nr); 849 } 850 EXPORT_SYMBOL(dump_emit); 851 852 void dump_skip_to(struct coredump_params *cprm, unsigned long pos) 853 { 854 cprm->to_skip = pos - cprm->pos; 855 } 856 EXPORT_SYMBOL(dump_skip_to); 857 858 void dump_skip(struct coredump_params *cprm, size_t nr) 859 { 860 cprm->to_skip += nr; 861 } 862 EXPORT_SYMBOL(dump_skip); 863 864 #ifdef CONFIG_ELF_CORE 865 static int dump_emit_page(struct coredump_params *cprm, struct page *page) 866 { 867 struct bio_vec bvec; 868 struct iov_iter iter; 869 struct file *file = cprm->file; 870 loff_t pos; 871 ssize_t n; 872 873 if (cprm->to_skip) { 874 if (!__dump_skip(cprm, cprm->to_skip)) 875 return 0; 876 cprm->to_skip = 0; 877 } 878 if (cprm->written + PAGE_SIZE > cprm->limit) 879 return 0; 880 if (dump_interrupted()) 881 return 0; 882 pos = file->f_pos; 883 bvec_set_page(&bvec, page, PAGE_SIZE, 0); 884 iov_iter_bvec(&iter, ITER_SOURCE, &bvec, 1, PAGE_SIZE); 885 iov_iter_set_copy_mc(&iter); 886 n = __kernel_write_iter(cprm->file, &iter, &pos); 887 if (n != PAGE_SIZE) 888 return 0; 889 file->f_pos = pos; 890 cprm->written += PAGE_SIZE; 891 cprm->pos += PAGE_SIZE; 892 893 return 1; 894 } 895 896 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 vma_iterator *vmi, 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 = vma_next(vmi); 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 VMA_ITERATOR(vmi, mm, 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(&vmi, 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