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 default: 329 break; 330 } 331 ++pat_ptr; 332 } 333 334 if (err) 335 return err; 336 } 337 338 out: 339 /* Backward compatibility with core_uses_pid: 340 * 341 * If core_pattern does not include a %p (as is the default) 342 * and core_uses_pid is set, then .%pid will be appended to 343 * the filename. Do not do this for piped commands. */ 344 if (!ispipe && !pid_in_pattern && core_uses_pid) { 345 err = cn_printf(cn, ".%d", task_tgid_vnr(current)); 346 if (err) 347 return err; 348 } 349 return ispipe; 350 } 351 352 static int zap_process(struct task_struct *start, int exit_code) 353 { 354 struct task_struct *t; 355 int nr = 0; 356 357 /* ignore all signals except SIGKILL, see prepare_signal() */ 358 start->signal->flags = SIGNAL_GROUP_EXIT; 359 start->signal->group_exit_code = exit_code; 360 start->signal->group_stop_count = 0; 361 362 for_each_thread(start, t) { 363 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK); 364 if (t != current && !(t->flags & PF_POSTCOREDUMP)) { 365 sigaddset(&t->pending.signal, SIGKILL); 366 signal_wake_up(t, 1); 367 nr++; 368 } 369 } 370 371 return nr; 372 } 373 374 static int zap_threads(struct task_struct *tsk, 375 struct core_state *core_state, int exit_code) 376 { 377 struct signal_struct *signal = tsk->signal; 378 int nr = -EAGAIN; 379 380 spin_lock_irq(&tsk->sighand->siglock); 381 if (!(signal->flags & SIGNAL_GROUP_EXIT) && !signal->group_exec_task) { 382 signal->core_state = core_state; 383 nr = zap_process(tsk, exit_code); 384 clear_tsk_thread_flag(tsk, TIF_SIGPENDING); 385 tsk->flags |= PF_DUMPCORE; 386 atomic_set(&core_state->nr_threads, nr); 387 } 388 spin_unlock_irq(&tsk->sighand->siglock); 389 return nr; 390 } 391 392 static int coredump_wait(int exit_code, struct core_state *core_state) 393 { 394 struct task_struct *tsk = current; 395 int core_waiters = -EBUSY; 396 397 init_completion(&core_state->startup); 398 core_state->dumper.task = tsk; 399 core_state->dumper.next = NULL; 400 401 core_waiters = zap_threads(tsk, core_state, exit_code); 402 if (core_waiters > 0) { 403 struct core_thread *ptr; 404 405 freezer_do_not_count(); 406 wait_for_completion(&core_state->startup); 407 freezer_count(); 408 /* 409 * Wait for all the threads to become inactive, so that 410 * all the thread context (extended register state, like 411 * fpu etc) gets copied to the memory. 412 */ 413 ptr = core_state->dumper.next; 414 while (ptr != NULL) { 415 wait_task_inactive(ptr->task, 0); 416 ptr = ptr->next; 417 } 418 } 419 420 return core_waiters; 421 } 422 423 static void coredump_finish(bool core_dumped) 424 { 425 struct core_thread *curr, *next; 426 struct task_struct *task; 427 428 spin_lock_irq(¤t->sighand->siglock); 429 if (core_dumped && !__fatal_signal_pending(current)) 430 current->signal->group_exit_code |= 0x80; 431 next = current->signal->core_state->dumper.next; 432 current->signal->core_state = NULL; 433 spin_unlock_irq(¤t->sighand->siglock); 434 435 while ((curr = next) != NULL) { 436 next = curr->next; 437 task = curr->task; 438 /* 439 * see coredump_task_exit(), curr->task must not see 440 * ->task == NULL before we read ->next. 441 */ 442 smp_mb(); 443 curr->task = NULL; 444 wake_up_process(task); 445 } 446 } 447 448 static bool dump_interrupted(void) 449 { 450 /* 451 * SIGKILL or freezing() interrupt the coredumping. Perhaps we 452 * can do try_to_freeze() and check __fatal_signal_pending(), 453 * but then we need to teach dump_write() to restart and clear 454 * TIF_SIGPENDING. 455 */ 456 return fatal_signal_pending(current) || freezing(current); 457 } 458 459 static void wait_for_dump_helpers(struct file *file) 460 { 461 struct pipe_inode_info *pipe = file->private_data; 462 463 pipe_lock(pipe); 464 pipe->readers++; 465 pipe->writers--; 466 wake_up_interruptible_sync(&pipe->rd_wait); 467 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 468 pipe_unlock(pipe); 469 470 /* 471 * We actually want wait_event_freezable() but then we need 472 * to clear TIF_SIGPENDING and improve dump_interrupted(). 473 */ 474 wait_event_interruptible(pipe->rd_wait, pipe->readers == 1); 475 476 pipe_lock(pipe); 477 pipe->readers--; 478 pipe->writers++; 479 pipe_unlock(pipe); 480 } 481 482 /* 483 * umh_pipe_setup 484 * helper function to customize the process used 485 * to collect the core in userspace. Specifically 486 * it sets up a pipe and installs it as fd 0 (stdin) 487 * for the process. Returns 0 on success, or 488 * PTR_ERR on failure. 489 * Note that it also sets the core limit to 1. This 490 * is a special value that we use to trap recursive 491 * core dumps 492 */ 493 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new) 494 { 495 struct file *files[2]; 496 struct coredump_params *cp = (struct coredump_params *)info->data; 497 int err = create_pipe_files(files, 0); 498 if (err) 499 return err; 500 501 cp->file = files[1]; 502 503 err = replace_fd(0, files[0], 0); 504 fput(files[0]); 505 /* and disallow core files too */ 506 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1}; 507 508 return err; 509 } 510 511 void do_coredump(const kernel_siginfo_t *siginfo) 512 { 513 struct core_state core_state; 514 struct core_name cn; 515 struct mm_struct *mm = current->mm; 516 struct linux_binfmt * binfmt; 517 const struct cred *old_cred; 518 struct cred *cred; 519 int retval = 0; 520 int ispipe; 521 size_t *argv = NULL; 522 int argc = 0; 523 /* require nonrelative corefile path and be extra careful */ 524 bool need_suid_safe = false; 525 bool core_dumped = false; 526 static atomic_t core_dump_count = ATOMIC_INIT(0); 527 struct coredump_params cprm = { 528 .siginfo = siginfo, 529 .regs = signal_pt_regs(), 530 .limit = rlimit(RLIMIT_CORE), 531 /* 532 * We must use the same mm->flags while dumping core to avoid 533 * inconsistency of bit flags, since this flag is not protected 534 * by any locks. 535 */ 536 .mm_flags = mm->flags, 537 .vma_meta = NULL, 538 }; 539 540 audit_core_dumps(siginfo->si_signo); 541 542 binfmt = mm->binfmt; 543 if (!binfmt || !binfmt->core_dump) 544 goto fail; 545 if (!__get_dumpable(cprm.mm_flags)) 546 goto fail; 547 548 cred = prepare_creds(); 549 if (!cred) 550 goto fail; 551 /* 552 * We cannot trust fsuid as being the "true" uid of the process 553 * nor do we know its entire history. We only know it was tainted 554 * so we dump it as root in mode 2, and only into a controlled 555 * environment (pipe handler or fully qualified path). 556 */ 557 if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) { 558 /* Setuid core dump mode */ 559 cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */ 560 need_suid_safe = true; 561 } 562 563 retval = coredump_wait(siginfo->si_signo, &core_state); 564 if (retval < 0) 565 goto fail_creds; 566 567 old_cred = override_creds(cred); 568 569 ispipe = format_corename(&cn, &cprm, &argv, &argc); 570 571 if (ispipe) { 572 int argi; 573 int dump_count; 574 char **helper_argv; 575 struct subprocess_info *sub_info; 576 577 if (ispipe < 0) { 578 printk(KERN_WARNING "format_corename failed\n"); 579 printk(KERN_WARNING "Aborting core\n"); 580 goto fail_unlock; 581 } 582 583 if (cprm.limit == 1) { 584 /* See umh_pipe_setup() which sets RLIMIT_CORE = 1. 585 * 586 * Normally core limits are irrelevant to pipes, since 587 * we're not writing to the file system, but we use 588 * cprm.limit of 1 here as a special value, this is a 589 * consistent way to catch recursive crashes. 590 * We can still crash if the core_pattern binary sets 591 * RLIM_CORE = !1, but it runs as root, and can do 592 * lots of stupid things. 593 * 594 * Note that we use task_tgid_vnr here to grab the pid 595 * of the process group leader. That way we get the 596 * right pid if a thread in a multi-threaded 597 * core_pattern process dies. 598 */ 599 printk(KERN_WARNING 600 "Process %d(%s) has RLIMIT_CORE set to 1\n", 601 task_tgid_vnr(current), current->comm); 602 printk(KERN_WARNING "Aborting core\n"); 603 goto fail_unlock; 604 } 605 cprm.limit = RLIM_INFINITY; 606 607 dump_count = atomic_inc_return(&core_dump_count); 608 if (core_pipe_limit && (core_pipe_limit < dump_count)) { 609 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n", 610 task_tgid_vnr(current), current->comm); 611 printk(KERN_WARNING "Skipping core dump\n"); 612 goto fail_dropcount; 613 } 614 615 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv), 616 GFP_KERNEL); 617 if (!helper_argv) { 618 printk(KERN_WARNING "%s failed to allocate memory\n", 619 __func__); 620 goto fail_dropcount; 621 } 622 for (argi = 0; argi < argc; argi++) 623 helper_argv[argi] = cn.corename + argv[argi]; 624 helper_argv[argi] = NULL; 625 626 retval = -ENOMEM; 627 sub_info = call_usermodehelper_setup(helper_argv[0], 628 helper_argv, NULL, GFP_KERNEL, 629 umh_pipe_setup, NULL, &cprm); 630 if (sub_info) 631 retval = call_usermodehelper_exec(sub_info, 632 UMH_WAIT_EXEC); 633 634 kfree(helper_argv); 635 if (retval) { 636 printk(KERN_INFO "Core dump to |%s pipe failed\n", 637 cn.corename); 638 goto close_fail; 639 } 640 } else { 641 struct user_namespace *mnt_userns; 642 struct inode *inode; 643 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW | 644 O_LARGEFILE | O_EXCL; 645 646 if (cprm.limit < binfmt->min_coredump) 647 goto fail_unlock; 648 649 if (need_suid_safe && cn.corename[0] != '/') { 650 printk(KERN_WARNING "Pid %d(%s) can only dump core "\ 651 "to fully qualified path!\n", 652 task_tgid_vnr(current), current->comm); 653 printk(KERN_WARNING "Skipping core dump\n"); 654 goto fail_unlock; 655 } 656 657 /* 658 * Unlink the file if it exists unless this is a SUID 659 * binary - in that case, we're running around with root 660 * privs and don't want to unlink another user's coredump. 661 */ 662 if (!need_suid_safe) { 663 /* 664 * If it doesn't exist, that's fine. If there's some 665 * other problem, we'll catch it at the filp_open(). 666 */ 667 do_unlinkat(AT_FDCWD, getname_kernel(cn.corename)); 668 } 669 670 /* 671 * There is a race between unlinking and creating the 672 * file, but if that causes an EEXIST here, that's 673 * fine - another process raced with us while creating 674 * the corefile, and the other process won. To userspace, 675 * what matters is that at least one of the two processes 676 * writes its coredump successfully, not which one. 677 */ 678 if (need_suid_safe) { 679 /* 680 * Using user namespaces, normal user tasks can change 681 * their current->fs->root to point to arbitrary 682 * directories. Since the intention of the "only dump 683 * with a fully qualified path" rule is to control where 684 * coredumps may be placed using root privileges, 685 * current->fs->root must not be used. Instead, use the 686 * root directory of init_task. 687 */ 688 struct path root; 689 690 task_lock(&init_task); 691 get_fs_root(init_task.fs, &root); 692 task_unlock(&init_task); 693 cprm.file = file_open_root(&root, cn.corename, 694 open_flags, 0600); 695 path_put(&root); 696 } else { 697 cprm.file = filp_open(cn.corename, open_flags, 0600); 698 } 699 if (IS_ERR(cprm.file)) 700 goto fail_unlock; 701 702 inode = file_inode(cprm.file); 703 if (inode->i_nlink > 1) 704 goto close_fail; 705 if (d_unhashed(cprm.file->f_path.dentry)) 706 goto close_fail; 707 /* 708 * AK: actually i see no reason to not allow this for named 709 * pipes etc, but keep the previous behaviour for now. 710 */ 711 if (!S_ISREG(inode->i_mode)) 712 goto close_fail; 713 /* 714 * Don't dump core if the filesystem changed owner or mode 715 * of the file during file creation. This is an issue when 716 * a process dumps core while its cwd is e.g. on a vfat 717 * filesystem. 718 */ 719 mnt_userns = file_mnt_user_ns(cprm.file); 720 if (!uid_eq(i_uid_into_mnt(mnt_userns, inode), 721 current_fsuid())) { 722 pr_info_ratelimited("Core dump to %s aborted: cannot preserve file owner\n", 723 cn.corename); 724 goto close_fail; 725 } 726 if ((inode->i_mode & 0677) != 0600) { 727 pr_info_ratelimited("Core dump to %s aborted: cannot preserve file permissions\n", 728 cn.corename); 729 goto close_fail; 730 } 731 if (!(cprm.file->f_mode & FMODE_CAN_WRITE)) 732 goto close_fail; 733 if (do_truncate(mnt_userns, cprm.file->f_path.dentry, 734 0, 0, cprm.file)) 735 goto close_fail; 736 } 737 738 /* get us an unshared descriptor table; almost always a no-op */ 739 /* The cell spufs coredump code reads the file descriptor tables */ 740 retval = unshare_files(); 741 if (retval) 742 goto close_fail; 743 if (!dump_interrupted()) { 744 /* 745 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would 746 * have this set to NULL. 747 */ 748 if (!cprm.file) { 749 pr_info("Core dump to |%s disabled\n", cn.corename); 750 goto close_fail; 751 } 752 if (!dump_vma_snapshot(&cprm)) 753 goto close_fail; 754 755 file_start_write(cprm.file); 756 core_dumped = binfmt->core_dump(&cprm); 757 /* 758 * Ensures that file size is big enough to contain the current 759 * file postion. This prevents gdb from complaining about 760 * a truncated file if the last "write" to the file was 761 * dump_skip. 762 */ 763 if (cprm.to_skip) { 764 cprm.to_skip--; 765 dump_emit(&cprm, "", 1); 766 } 767 file_end_write(cprm.file); 768 free_vma_snapshot(&cprm); 769 } 770 if (ispipe && core_pipe_limit) 771 wait_for_dump_helpers(cprm.file); 772 close_fail: 773 if (cprm.file) 774 filp_close(cprm.file, NULL); 775 fail_dropcount: 776 if (ispipe) 777 atomic_dec(&core_dump_count); 778 fail_unlock: 779 kfree(argv); 780 kfree(cn.corename); 781 coredump_finish(core_dumped); 782 revert_creds(old_cred); 783 fail_creds: 784 put_cred(cred); 785 fail: 786 return; 787 } 788 789 /* 790 * Core dumping helper functions. These are the only things you should 791 * do on a core-file: use only these functions to write out all the 792 * necessary info. 793 */ 794 static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr) 795 { 796 struct file *file = cprm->file; 797 loff_t pos = file->f_pos; 798 ssize_t n; 799 if (cprm->written + nr > cprm->limit) 800 return 0; 801 802 803 if (dump_interrupted()) 804 return 0; 805 n = __kernel_write(file, addr, nr, &pos); 806 if (n != nr) 807 return 0; 808 file->f_pos = pos; 809 cprm->written += n; 810 cprm->pos += n; 811 812 return 1; 813 } 814 815 static int __dump_skip(struct coredump_params *cprm, size_t nr) 816 { 817 static char zeroes[PAGE_SIZE]; 818 struct file *file = cprm->file; 819 if (file->f_mode & FMODE_LSEEK) { 820 if (dump_interrupted() || 821 vfs_llseek(file, nr, SEEK_CUR) < 0) 822 return 0; 823 cprm->pos += nr; 824 return 1; 825 } else { 826 while (nr > PAGE_SIZE) { 827 if (!__dump_emit(cprm, zeroes, PAGE_SIZE)) 828 return 0; 829 nr -= PAGE_SIZE; 830 } 831 return __dump_emit(cprm, zeroes, nr); 832 } 833 } 834 835 int dump_emit(struct coredump_params *cprm, const void *addr, int nr) 836 { 837 if (cprm->to_skip) { 838 if (!__dump_skip(cprm, cprm->to_skip)) 839 return 0; 840 cprm->to_skip = 0; 841 } 842 return __dump_emit(cprm, addr, nr); 843 } 844 EXPORT_SYMBOL(dump_emit); 845 846 void dump_skip_to(struct coredump_params *cprm, unsigned long pos) 847 { 848 cprm->to_skip = pos - cprm->pos; 849 } 850 EXPORT_SYMBOL(dump_skip_to); 851 852 void dump_skip(struct coredump_params *cprm, size_t nr) 853 { 854 cprm->to_skip += nr; 855 } 856 EXPORT_SYMBOL(dump_skip); 857 858 #ifdef CONFIG_ELF_CORE 859 int dump_user_range(struct coredump_params *cprm, unsigned long start, 860 unsigned long len) 861 { 862 unsigned long addr; 863 864 for (addr = start; addr < start + len; addr += PAGE_SIZE) { 865 struct page *page; 866 int stop; 867 868 /* 869 * To avoid having to allocate page tables for virtual address 870 * ranges that have never been used yet, and also to make it 871 * easy to generate sparse core files, use a helper that returns 872 * NULL when encountering an empty page table entry that would 873 * otherwise have been filled with the zero page. 874 */ 875 page = get_dump_page(addr); 876 if (page) { 877 void *kaddr = kmap_local_page(page); 878 879 stop = !dump_emit(cprm, kaddr, PAGE_SIZE); 880 kunmap_local(kaddr); 881 put_page(page); 882 if (stop) 883 return 0; 884 } else { 885 dump_skip(cprm, PAGE_SIZE); 886 } 887 } 888 return 1; 889 } 890 #endif 891 892 int dump_align(struct coredump_params *cprm, int align) 893 { 894 unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1); 895 if (align & (align - 1)) 896 return 0; 897 if (mod) 898 cprm->to_skip += align - mod; 899 return 1; 900 } 901 EXPORT_SYMBOL(dump_align); 902 903 #ifdef CONFIG_SYSCTL 904 905 void validate_coredump_safety(void) 906 { 907 if (suid_dumpable == SUID_DUMP_ROOT && 908 core_pattern[0] != '/' && core_pattern[0] != '|') { 909 pr_warn( 910 "Unsafe core_pattern used with fs.suid_dumpable=2.\n" 911 "Pipe handler or fully qualified core dump path required.\n" 912 "Set kernel.core_pattern before fs.suid_dumpable.\n" 913 ); 914 } 915 } 916 917 static int proc_dostring_coredump(struct ctl_table *table, int write, 918 void *buffer, size_t *lenp, loff_t *ppos) 919 { 920 int error = proc_dostring(table, write, buffer, lenp, ppos); 921 922 if (!error) 923 validate_coredump_safety(); 924 return error; 925 } 926 927 static struct ctl_table coredump_sysctls[] = { 928 { 929 .procname = "core_uses_pid", 930 .data = &core_uses_pid, 931 .maxlen = sizeof(int), 932 .mode = 0644, 933 .proc_handler = proc_dointvec, 934 }, 935 { 936 .procname = "core_pattern", 937 .data = core_pattern, 938 .maxlen = CORENAME_MAX_SIZE, 939 .mode = 0644, 940 .proc_handler = proc_dostring_coredump, 941 }, 942 { 943 .procname = "core_pipe_limit", 944 .data = &core_pipe_limit, 945 .maxlen = sizeof(unsigned int), 946 .mode = 0644, 947 .proc_handler = proc_dointvec, 948 }, 949 { } 950 }; 951 952 static int __init init_fs_coredump_sysctls(void) 953 { 954 register_sysctl_init("kernel", coredump_sysctls); 955 return 0; 956 } 957 fs_initcall(init_fs_coredump_sysctls); 958 #endif /* CONFIG_SYSCTL */ 959 960 /* 961 * The purpose of always_dump_vma() is to make sure that special kernel mappings 962 * that are useful for post-mortem analysis are included in every core dump. 963 * In that way we ensure that the core dump is fully interpretable later 964 * without matching up the same kernel and hardware config to see what PC values 965 * meant. These special mappings include - vDSO, vsyscall, and other 966 * architecture specific mappings 967 */ 968 static bool always_dump_vma(struct vm_area_struct *vma) 969 { 970 /* Any vsyscall mappings? */ 971 if (vma == get_gate_vma(vma->vm_mm)) 972 return true; 973 974 /* 975 * Assume that all vmas with a .name op should always be dumped. 976 * If this changes, a new vm_ops field can easily be added. 977 */ 978 if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma)) 979 return true; 980 981 /* 982 * arch_vma_name() returns non-NULL for special architecture mappings, 983 * such as vDSO sections. 984 */ 985 if (arch_vma_name(vma)) 986 return true; 987 988 return false; 989 } 990 991 #define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1 992 993 /* 994 * Decide how much of @vma's contents should be included in a core dump. 995 */ 996 static unsigned long vma_dump_size(struct vm_area_struct *vma, 997 unsigned long mm_flags) 998 { 999 #define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type)) 1000 1001 /* always dump the vdso and vsyscall sections */ 1002 if (always_dump_vma(vma)) 1003 goto whole; 1004 1005 if (vma->vm_flags & VM_DONTDUMP) 1006 return 0; 1007 1008 /* support for DAX */ 1009 if (vma_is_dax(vma)) { 1010 if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED)) 1011 goto whole; 1012 if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE)) 1013 goto whole; 1014 return 0; 1015 } 1016 1017 /* Hugetlb memory check */ 1018 if (is_vm_hugetlb_page(vma)) { 1019 if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED)) 1020 goto whole; 1021 if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE)) 1022 goto whole; 1023 return 0; 1024 } 1025 1026 /* Do not dump I/O mapped devices or special mappings */ 1027 if (vma->vm_flags & VM_IO) 1028 return 0; 1029 1030 /* By default, dump shared memory if mapped from an anonymous file. */ 1031 if (vma->vm_flags & VM_SHARED) { 1032 if (file_inode(vma->vm_file)->i_nlink == 0 ? 1033 FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED)) 1034 goto whole; 1035 return 0; 1036 } 1037 1038 /* Dump segments that have been written to. */ 1039 if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE)) 1040 goto whole; 1041 if (vma->vm_file == NULL) 1042 return 0; 1043 1044 if (FILTER(MAPPED_PRIVATE)) 1045 goto whole; 1046 1047 /* 1048 * If this is the beginning of an executable file mapping, 1049 * dump the first page to aid in determining what was mapped here. 1050 */ 1051 if (FILTER(ELF_HEADERS) && 1052 vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) { 1053 if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0) 1054 return PAGE_SIZE; 1055 1056 /* 1057 * ELF libraries aren't always executable. 1058 * We'll want to check whether the mapping starts with the ELF 1059 * magic, but not now - we're holding the mmap lock, 1060 * so copy_from_user() doesn't work here. 1061 * Use a placeholder instead, and fix it up later in 1062 * dump_vma_snapshot(). 1063 */ 1064 return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER; 1065 } 1066 1067 #undef FILTER 1068 1069 return 0; 1070 1071 whole: 1072 return vma->vm_end - vma->vm_start; 1073 } 1074 1075 static struct vm_area_struct *first_vma(struct task_struct *tsk, 1076 struct vm_area_struct *gate_vma) 1077 { 1078 struct vm_area_struct *ret = tsk->mm->mmap; 1079 1080 if (ret) 1081 return ret; 1082 return gate_vma; 1083 } 1084 1085 /* 1086 * Helper function for iterating across a vma list. It ensures that the caller 1087 * will visit `gate_vma' prior to terminating the search. 1088 */ 1089 static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma, 1090 struct vm_area_struct *gate_vma) 1091 { 1092 struct vm_area_struct *ret; 1093 1094 ret = this_vma->vm_next; 1095 if (ret) 1096 return ret; 1097 if (this_vma == gate_vma) 1098 return NULL; 1099 return gate_vma; 1100 } 1101 1102 static void free_vma_snapshot(struct coredump_params *cprm) 1103 { 1104 if (cprm->vma_meta) { 1105 int i; 1106 for (i = 0; i < cprm->vma_count; i++) { 1107 struct file *file = cprm->vma_meta[i].file; 1108 if (file) 1109 fput(file); 1110 } 1111 kvfree(cprm->vma_meta); 1112 cprm->vma_meta = NULL; 1113 } 1114 } 1115 1116 /* 1117 * Under the mmap_lock, take a snapshot of relevant information about the task's 1118 * VMAs. 1119 */ 1120 static bool dump_vma_snapshot(struct coredump_params *cprm) 1121 { 1122 struct vm_area_struct *vma, *gate_vma; 1123 struct mm_struct *mm = current->mm; 1124 int i; 1125 1126 /* 1127 * Once the stack expansion code is fixed to not change VMA bounds 1128 * under mmap_lock in read mode, this can be changed to take the 1129 * mmap_lock in read mode. 1130 */ 1131 if (mmap_write_lock_killable(mm)) 1132 return false; 1133 1134 cprm->vma_data_size = 0; 1135 gate_vma = get_gate_vma(mm); 1136 cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0); 1137 1138 cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL); 1139 if (!cprm->vma_meta) { 1140 mmap_write_unlock(mm); 1141 return false; 1142 } 1143 1144 for (i = 0, vma = first_vma(current, gate_vma); vma != NULL; 1145 vma = next_vma(vma, gate_vma), i++) { 1146 struct core_vma_metadata *m = cprm->vma_meta + i; 1147 1148 m->start = vma->vm_start; 1149 m->end = vma->vm_end; 1150 m->flags = vma->vm_flags; 1151 m->dump_size = vma_dump_size(vma, cprm->mm_flags); 1152 m->pgoff = vma->vm_pgoff; 1153 1154 m->file = vma->vm_file; 1155 if (m->file) 1156 get_file(m->file); 1157 } 1158 1159 mmap_write_unlock(mm); 1160 1161 for (i = 0; i < cprm->vma_count; i++) { 1162 struct core_vma_metadata *m = cprm->vma_meta + i; 1163 1164 if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) { 1165 char elfmag[SELFMAG]; 1166 1167 if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) || 1168 memcmp(elfmag, ELFMAG, SELFMAG) != 0) { 1169 m->dump_size = 0; 1170 } else { 1171 m->dump_size = PAGE_SIZE; 1172 } 1173 } 1174 1175 cprm->vma_data_size += m->dump_size; 1176 } 1177 1178 return true; 1179 } 1180