GNU Linux-libre 5.19-rc6-gnu
[releases.git] / fs / coredump.c
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(&current->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(&current->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_op->llseek && file->f_op->llseek != no_llseek) {
820                 if (dump_interrupted() ||
821                     file->f_op->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 }