xref: /openbmc/linux/fs/coredump.c (revision ee7da21a)
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/tracehook.h>
35  #include <linux/kmod.h>
36  #include <linux/fsnotify.h>
37  #include <linux/fs_struct.h>
38  #include <linux/pipe_fs_i.h>
39  #include <linux/oom.h>
40  #include <linux/compat.h>
41  #include <linux/fs.h>
42  #include <linux/path.h>
43  #include <linux/timekeeping.h>
44  
45  #include <linux/uaccess.h>
46  #include <asm/mmu_context.h>
47  #include <asm/tlb.h>
48  #include <asm/exec.h>
49  
50  #include <trace/events/task.h>
51  #include "internal.h"
52  
53  #include <trace/events/sched.h>
54  
55  int core_uses_pid;
56  unsigned int core_pipe_limit;
57  char core_pattern[CORENAME_MAX_SIZE] = "core";
58  static int core_name_size = CORENAME_MAX_SIZE;
59  
60  struct core_name {
61  	char *corename;
62  	int used, size;
63  };
64  
65  /* The maximal length of core_pattern is also specified in sysctl.c */
66  
67  static int expand_corename(struct core_name *cn, int size)
68  {
69  	char *corename = krealloc(cn->corename, size, GFP_KERNEL);
70  
71  	if (!corename)
72  		return -ENOMEM;
73  
74  	if (size > core_name_size) /* racy but harmless */
75  		core_name_size = size;
76  
77  	cn->size = ksize(corename);
78  	cn->corename = corename;
79  	return 0;
80  }
81  
82  static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
83  				     va_list arg)
84  {
85  	int free, need;
86  	va_list arg_copy;
87  
88  again:
89  	free = cn->size - cn->used;
90  
91  	va_copy(arg_copy, arg);
92  	need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
93  	va_end(arg_copy);
94  
95  	if (need < free) {
96  		cn->used += need;
97  		return 0;
98  	}
99  
100  	if (!expand_corename(cn, cn->size + need - free + 1))
101  		goto again;
102  
103  	return -ENOMEM;
104  }
105  
106  static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
107  {
108  	va_list arg;
109  	int ret;
110  
111  	va_start(arg, fmt);
112  	ret = cn_vprintf(cn, fmt, arg);
113  	va_end(arg);
114  
115  	return ret;
116  }
117  
118  static __printf(2, 3)
119  int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
120  {
121  	int cur = cn->used;
122  	va_list arg;
123  	int ret;
124  
125  	va_start(arg, fmt);
126  	ret = cn_vprintf(cn, fmt, arg);
127  	va_end(arg);
128  
129  	if (ret == 0) {
130  		/*
131  		 * Ensure that this coredump name component can't cause the
132  		 * resulting corefile path to consist of a ".." or ".".
133  		 */
134  		if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
135  				(cn->used - cur == 2 && cn->corename[cur] == '.'
136  				&& cn->corename[cur+1] == '.'))
137  			cn->corename[cur] = '!';
138  
139  		/*
140  		 * Empty names are fishy and could be used to create a "//" in a
141  		 * corefile name, causing the coredump to happen one directory
142  		 * level too high. Enforce that all components of the core
143  		 * pattern are at least one character long.
144  		 */
145  		if (cn->used == cur)
146  			ret = cn_printf(cn, "!");
147  	}
148  
149  	for (; cur < cn->used; ++cur) {
150  		if (cn->corename[cur] == '/')
151  			cn->corename[cur] = '!';
152  	}
153  	return ret;
154  }
155  
156  static int cn_print_exe_file(struct core_name *cn, bool name_only)
157  {
158  	struct file *exe_file;
159  	char *pathbuf, *path, *ptr;
160  	int ret;
161  
162  	exe_file = get_mm_exe_file(current->mm);
163  	if (!exe_file)
164  		return cn_esc_printf(cn, "%s (path unknown)", current->comm);
165  
166  	pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
167  	if (!pathbuf) {
168  		ret = -ENOMEM;
169  		goto put_exe_file;
170  	}
171  
172  	path = file_path(exe_file, pathbuf, PATH_MAX);
173  	if (IS_ERR(path)) {
174  		ret = PTR_ERR(path);
175  		goto free_buf;
176  	}
177  
178  	if (name_only) {
179  		ptr = strrchr(path, '/');
180  		if (ptr)
181  			path = ptr + 1;
182  	}
183  	ret = cn_esc_printf(cn, "%s", path);
184  
185  free_buf:
186  	kfree(pathbuf);
187  put_exe_file:
188  	fput(exe_file);
189  	return ret;
190  }
191  
192  /* format_corename will inspect the pattern parameter, and output a
193   * name into corename, which must have space for at least
194   * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
195   */
196  static int format_corename(struct core_name *cn, struct coredump_params *cprm,
197  			   size_t **argv, int *argc)
198  {
199  	const struct cred *cred = current_cred();
200  	const char *pat_ptr = core_pattern;
201  	int ispipe = (*pat_ptr == '|');
202  	bool was_space = false;
203  	int pid_in_pattern = 0;
204  	int err = 0;
205  
206  	cn->used = 0;
207  	cn->corename = NULL;
208  	if (expand_corename(cn, core_name_size))
209  		return -ENOMEM;
210  	cn->corename[0] = '\0';
211  
212  	if (ispipe) {
213  		int argvs = sizeof(core_pattern) / 2;
214  		(*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
215  		if (!(*argv))
216  			return -ENOMEM;
217  		(*argv)[(*argc)++] = 0;
218  		++pat_ptr;
219  		if (!(*pat_ptr))
220  			return -ENOMEM;
221  	}
222  
223  	/* Repeat as long as we have more pattern to process and more output
224  	   space */
225  	while (*pat_ptr) {
226  		/*
227  		 * Split on spaces before doing template expansion so that
228  		 * %e and %E don't get split if they have spaces in them
229  		 */
230  		if (ispipe) {
231  			if (isspace(*pat_ptr)) {
232  				if (cn->used != 0)
233  					was_space = true;
234  				pat_ptr++;
235  				continue;
236  			} else if (was_space) {
237  				was_space = false;
238  				err = cn_printf(cn, "%c", '\0');
239  				if (err)
240  					return err;
241  				(*argv)[(*argc)++] = cn->used;
242  			}
243  		}
244  		if (*pat_ptr != '%') {
245  			err = cn_printf(cn, "%c", *pat_ptr++);
246  		} else {
247  			switch (*++pat_ptr) {
248  			/* single % at the end, drop that */
249  			case 0:
250  				goto out;
251  			/* Double percent, output one percent */
252  			case '%':
253  				err = cn_printf(cn, "%c", '%');
254  				break;
255  			/* pid */
256  			case 'p':
257  				pid_in_pattern = 1;
258  				err = cn_printf(cn, "%d",
259  					      task_tgid_vnr(current));
260  				break;
261  			/* global pid */
262  			case 'P':
263  				err = cn_printf(cn, "%d",
264  					      task_tgid_nr(current));
265  				break;
266  			case 'i':
267  				err = cn_printf(cn, "%d",
268  					      task_pid_vnr(current));
269  				break;
270  			case 'I':
271  				err = cn_printf(cn, "%d",
272  					      task_pid_nr(current));
273  				break;
274  			/* uid */
275  			case 'u':
276  				err = cn_printf(cn, "%u",
277  						from_kuid(&init_user_ns,
278  							  cred->uid));
279  				break;
280  			/* gid */
281  			case 'g':
282  				err = cn_printf(cn, "%u",
283  						from_kgid(&init_user_ns,
284  							  cred->gid));
285  				break;
286  			case 'd':
287  				err = cn_printf(cn, "%d",
288  					__get_dumpable(cprm->mm_flags));
289  				break;
290  			/* signal that caused the coredump */
291  			case 's':
292  				err = cn_printf(cn, "%d",
293  						cprm->siginfo->si_signo);
294  				break;
295  			/* UNIX time of coredump */
296  			case 't': {
297  				time64_t time;
298  
299  				time = ktime_get_real_seconds();
300  				err = cn_printf(cn, "%lld", time);
301  				break;
302  			}
303  			/* hostname */
304  			case 'h':
305  				down_read(&uts_sem);
306  				err = cn_esc_printf(cn, "%s",
307  					      utsname()->nodename);
308  				up_read(&uts_sem);
309  				break;
310  			/* executable, could be changed by prctl PR_SET_NAME etc */
311  			case 'e':
312  				err = cn_esc_printf(cn, "%s", current->comm);
313  				break;
314  			/* file name of executable */
315  			case 'f':
316  				err = cn_print_exe_file(cn, true);
317  				break;
318  			case 'E':
319  				err = cn_print_exe_file(cn, false);
320  				break;
321  			/* core limit size */
322  			case 'c':
323  				err = cn_printf(cn, "%lu",
324  					      rlimit(RLIMIT_CORE));
325  				break;
326  			default:
327  				break;
328  			}
329  			++pat_ptr;
330  		}
331  
332  		if (err)
333  			return err;
334  	}
335  
336  out:
337  	/* Backward compatibility with core_uses_pid:
338  	 *
339  	 * If core_pattern does not include a %p (as is the default)
340  	 * and core_uses_pid is set, then .%pid will be appended to
341  	 * the filename. Do not do this for piped commands. */
342  	if (!ispipe && !pid_in_pattern && core_uses_pid) {
343  		err = cn_printf(cn, ".%d", task_tgid_vnr(current));
344  		if (err)
345  			return err;
346  	}
347  	return ispipe;
348  }
349  
350  static int zap_process(struct task_struct *start, int exit_code, int flags)
351  {
352  	struct task_struct *t;
353  	int nr = 0;
354  
355  	/* ignore all signals except SIGKILL, see prepare_signal() */
356  	start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
357  	start->signal->group_exit_code = exit_code;
358  	start->signal->group_stop_count = 0;
359  
360  	for_each_thread(start, t) {
361  		task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
362  		if (t != current && t->mm) {
363  			sigaddset(&t->pending.signal, SIGKILL);
364  			signal_wake_up(t, 1);
365  			nr++;
366  		}
367  	}
368  
369  	return nr;
370  }
371  
372  static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
373  			struct core_state *core_state, int exit_code)
374  {
375  	struct task_struct *g, *p;
376  	unsigned long flags;
377  	int nr = -EAGAIN;
378  
379  	spin_lock_irq(&tsk->sighand->siglock);
380  	if (!signal_group_exit(tsk->signal)) {
381  		mm->core_state = core_state;
382  		tsk->signal->group_exit_task = tsk;
383  		nr = zap_process(tsk, exit_code, 0);
384  		clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
385  	}
386  	spin_unlock_irq(&tsk->sighand->siglock);
387  	if (unlikely(nr < 0))
388  		return nr;
389  
390  	tsk->flags |= PF_DUMPCORE;
391  	if (atomic_read(&mm->mm_users) == nr + 1)
392  		goto done;
393  	/*
394  	 * We should find and kill all tasks which use this mm, and we should
395  	 * count them correctly into ->nr_threads. We don't take tasklist
396  	 * lock, but this is safe wrt:
397  	 *
398  	 * fork:
399  	 *	None of sub-threads can fork after zap_process(leader). All
400  	 *	processes which were created before this point should be
401  	 *	visible to zap_threads() because copy_process() adds the new
402  	 *	process to the tail of init_task.tasks list, and lock/unlock
403  	 *	of ->siglock provides a memory barrier.
404  	 *
405  	 * do_exit:
406  	 *	The caller holds mm->mmap_lock. This means that the task which
407  	 *	uses this mm can't pass exit_mm(), so it can't exit or clear
408  	 *	its ->mm.
409  	 *
410  	 * de_thread:
411  	 *	It does list_replace_rcu(&leader->tasks, &current->tasks),
412  	 *	we must see either old or new leader, this does not matter.
413  	 *	However, it can change p->sighand, so lock_task_sighand(p)
414  	 *	must be used. Since p->mm != NULL and we hold ->mmap_lock
415  	 *	it can't fail.
416  	 *
417  	 *	Note also that "g" can be the old leader with ->mm == NULL
418  	 *	and already unhashed and thus removed from ->thread_group.
419  	 *	This is OK, __unhash_process()->list_del_rcu() does not
420  	 *	clear the ->next pointer, we will find the new leader via
421  	 *	next_thread().
422  	 */
423  	rcu_read_lock();
424  	for_each_process(g) {
425  		if (g == tsk->group_leader)
426  			continue;
427  		if (g->flags & PF_KTHREAD)
428  			continue;
429  
430  		for_each_thread(g, p) {
431  			if (unlikely(!p->mm))
432  				continue;
433  			if (unlikely(p->mm == mm)) {
434  				lock_task_sighand(p, &flags);
435  				nr += zap_process(p, exit_code,
436  							SIGNAL_GROUP_EXIT);
437  				unlock_task_sighand(p, &flags);
438  			}
439  			break;
440  		}
441  	}
442  	rcu_read_unlock();
443  done:
444  	atomic_set(&core_state->nr_threads, nr);
445  	return nr;
446  }
447  
448  static int coredump_wait(int exit_code, struct core_state *core_state)
449  {
450  	struct task_struct *tsk = current;
451  	struct mm_struct *mm = tsk->mm;
452  	int core_waiters = -EBUSY;
453  
454  	init_completion(&core_state->startup);
455  	core_state->dumper.task = tsk;
456  	core_state->dumper.next = NULL;
457  
458  	if (mmap_write_lock_killable(mm))
459  		return -EINTR;
460  
461  	if (!mm->core_state)
462  		core_waiters = zap_threads(tsk, mm, core_state, exit_code);
463  	mmap_write_unlock(mm);
464  
465  	if (core_waiters > 0) {
466  		struct core_thread *ptr;
467  
468  		freezer_do_not_count();
469  		wait_for_completion(&core_state->startup);
470  		freezer_count();
471  		/*
472  		 * Wait for all the threads to become inactive, so that
473  		 * all the thread context (extended register state, like
474  		 * fpu etc) gets copied to the memory.
475  		 */
476  		ptr = core_state->dumper.next;
477  		while (ptr != NULL) {
478  			wait_task_inactive(ptr->task, 0);
479  			ptr = ptr->next;
480  		}
481  	}
482  
483  	return core_waiters;
484  }
485  
486  static void coredump_finish(struct mm_struct *mm, bool core_dumped)
487  {
488  	struct core_thread *curr, *next;
489  	struct task_struct *task;
490  
491  	spin_lock_irq(&current->sighand->siglock);
492  	if (core_dumped && !__fatal_signal_pending(current))
493  		current->signal->group_exit_code |= 0x80;
494  	current->signal->group_exit_task = NULL;
495  	current->signal->flags = SIGNAL_GROUP_EXIT;
496  	spin_unlock_irq(&current->sighand->siglock);
497  
498  	next = mm->core_state->dumper.next;
499  	while ((curr = next) != NULL) {
500  		next = curr->next;
501  		task = curr->task;
502  		/*
503  		 * see exit_mm(), curr->task must not see
504  		 * ->task == NULL before we read ->next.
505  		 */
506  		smp_mb();
507  		curr->task = NULL;
508  		wake_up_process(task);
509  	}
510  
511  	mm->core_state = NULL;
512  }
513  
514  static bool dump_interrupted(void)
515  {
516  	/*
517  	 * SIGKILL or freezing() interrupt the coredumping. Perhaps we
518  	 * can do try_to_freeze() and check __fatal_signal_pending(),
519  	 * but then we need to teach dump_write() to restart and clear
520  	 * TIF_SIGPENDING.
521  	 */
522  	return fatal_signal_pending(current) || freezing(current);
523  }
524  
525  static void wait_for_dump_helpers(struct file *file)
526  {
527  	struct pipe_inode_info *pipe = file->private_data;
528  
529  	pipe_lock(pipe);
530  	pipe->readers++;
531  	pipe->writers--;
532  	wake_up_interruptible_sync(&pipe->rd_wait);
533  	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
534  	pipe_unlock(pipe);
535  
536  	/*
537  	 * We actually want wait_event_freezable() but then we need
538  	 * to clear TIF_SIGPENDING and improve dump_interrupted().
539  	 */
540  	wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
541  
542  	pipe_lock(pipe);
543  	pipe->readers--;
544  	pipe->writers++;
545  	pipe_unlock(pipe);
546  }
547  
548  /*
549   * umh_pipe_setup
550   * helper function to customize the process used
551   * to collect the core in userspace.  Specifically
552   * it sets up a pipe and installs it as fd 0 (stdin)
553   * for the process.  Returns 0 on success, or
554   * PTR_ERR on failure.
555   * Note that it also sets the core limit to 1.  This
556   * is a special value that we use to trap recursive
557   * core dumps
558   */
559  static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
560  {
561  	struct file *files[2];
562  	struct coredump_params *cp = (struct coredump_params *)info->data;
563  	int err = create_pipe_files(files, 0);
564  	if (err)
565  		return err;
566  
567  	cp->file = files[1];
568  
569  	err = replace_fd(0, files[0], 0);
570  	fput(files[0]);
571  	/* and disallow core files too */
572  	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
573  
574  	return err;
575  }
576  
577  void do_coredump(const kernel_siginfo_t *siginfo)
578  {
579  	struct core_state core_state;
580  	struct core_name cn;
581  	struct mm_struct *mm = current->mm;
582  	struct linux_binfmt * binfmt;
583  	const struct cred *old_cred;
584  	struct cred *cred;
585  	int retval = 0;
586  	int ispipe;
587  	size_t *argv = NULL;
588  	int argc = 0;
589  	/* require nonrelative corefile path and be extra careful */
590  	bool need_suid_safe = false;
591  	bool core_dumped = false;
592  	static atomic_t core_dump_count = ATOMIC_INIT(0);
593  	struct coredump_params cprm = {
594  		.siginfo = siginfo,
595  		.regs = signal_pt_regs(),
596  		.limit = rlimit(RLIMIT_CORE),
597  		/*
598  		 * We must use the same mm->flags while dumping core to avoid
599  		 * inconsistency of bit flags, since this flag is not protected
600  		 * by any locks.
601  		 */
602  		.mm_flags = mm->flags,
603  	};
604  
605  	audit_core_dumps(siginfo->si_signo);
606  
607  	binfmt = mm->binfmt;
608  	if (!binfmt || !binfmt->core_dump)
609  		goto fail;
610  	if (!__get_dumpable(cprm.mm_flags))
611  		goto fail;
612  
613  	cred = prepare_creds();
614  	if (!cred)
615  		goto fail;
616  	/*
617  	 * We cannot trust fsuid as being the "true" uid of the process
618  	 * nor do we know its entire history. We only know it was tainted
619  	 * so we dump it as root in mode 2, and only into a controlled
620  	 * environment (pipe handler or fully qualified path).
621  	 */
622  	if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
623  		/* Setuid core dump mode */
624  		cred->fsuid = GLOBAL_ROOT_UID;	/* Dump root private */
625  		need_suid_safe = true;
626  	}
627  
628  	retval = coredump_wait(siginfo->si_signo, &core_state);
629  	if (retval < 0)
630  		goto fail_creds;
631  
632  	old_cred = override_creds(cred);
633  
634  	ispipe = format_corename(&cn, &cprm, &argv, &argc);
635  
636  	if (ispipe) {
637  		int argi;
638  		int dump_count;
639  		char **helper_argv;
640  		struct subprocess_info *sub_info;
641  
642  		if (ispipe < 0) {
643  			printk(KERN_WARNING "format_corename failed\n");
644  			printk(KERN_WARNING "Aborting core\n");
645  			goto fail_unlock;
646  		}
647  
648  		if (cprm.limit == 1) {
649  			/* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
650  			 *
651  			 * Normally core limits are irrelevant to pipes, since
652  			 * we're not writing to the file system, but we use
653  			 * cprm.limit of 1 here as a special value, this is a
654  			 * consistent way to catch recursive crashes.
655  			 * We can still crash if the core_pattern binary sets
656  			 * RLIM_CORE = !1, but it runs as root, and can do
657  			 * lots of stupid things.
658  			 *
659  			 * Note that we use task_tgid_vnr here to grab the pid
660  			 * of the process group leader.  That way we get the
661  			 * right pid if a thread in a multi-threaded
662  			 * core_pattern process dies.
663  			 */
664  			printk(KERN_WARNING
665  				"Process %d(%s) has RLIMIT_CORE set to 1\n",
666  				task_tgid_vnr(current), current->comm);
667  			printk(KERN_WARNING "Aborting core\n");
668  			goto fail_unlock;
669  		}
670  		cprm.limit = RLIM_INFINITY;
671  
672  		dump_count = atomic_inc_return(&core_dump_count);
673  		if (core_pipe_limit && (core_pipe_limit < dump_count)) {
674  			printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
675  			       task_tgid_vnr(current), current->comm);
676  			printk(KERN_WARNING "Skipping core dump\n");
677  			goto fail_dropcount;
678  		}
679  
680  		helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
681  					    GFP_KERNEL);
682  		if (!helper_argv) {
683  			printk(KERN_WARNING "%s failed to allocate memory\n",
684  			       __func__);
685  			goto fail_dropcount;
686  		}
687  		for (argi = 0; argi < argc; argi++)
688  			helper_argv[argi] = cn.corename + argv[argi];
689  		helper_argv[argi] = NULL;
690  
691  		retval = -ENOMEM;
692  		sub_info = call_usermodehelper_setup(helper_argv[0],
693  						helper_argv, NULL, GFP_KERNEL,
694  						umh_pipe_setup, NULL, &cprm);
695  		if (sub_info)
696  			retval = call_usermodehelper_exec(sub_info,
697  							  UMH_WAIT_EXEC);
698  
699  		kfree(helper_argv);
700  		if (retval) {
701  			printk(KERN_INFO "Core dump to |%s pipe failed\n",
702  			       cn.corename);
703  			goto close_fail;
704  		}
705  	} else {
706  		struct user_namespace *mnt_userns;
707  		struct inode *inode;
708  		int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
709  				 O_LARGEFILE | O_EXCL;
710  
711  		if (cprm.limit < binfmt->min_coredump)
712  			goto fail_unlock;
713  
714  		if (need_suid_safe && cn.corename[0] != '/') {
715  			printk(KERN_WARNING "Pid %d(%s) can only dump core "\
716  				"to fully qualified path!\n",
717  				task_tgid_vnr(current), current->comm);
718  			printk(KERN_WARNING "Skipping core dump\n");
719  			goto fail_unlock;
720  		}
721  
722  		/*
723  		 * Unlink the file if it exists unless this is a SUID
724  		 * binary - in that case, we're running around with root
725  		 * privs and don't want to unlink another user's coredump.
726  		 */
727  		if (!need_suid_safe) {
728  			/*
729  			 * If it doesn't exist, that's fine. If there's some
730  			 * other problem, we'll catch it at the filp_open().
731  			 */
732  			do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
733  		}
734  
735  		/*
736  		 * There is a race between unlinking and creating the
737  		 * file, but if that causes an EEXIST here, that's
738  		 * fine - another process raced with us while creating
739  		 * the corefile, and the other process won. To userspace,
740  		 * what matters is that at least one of the two processes
741  		 * writes its coredump successfully, not which one.
742  		 */
743  		if (need_suid_safe) {
744  			/*
745  			 * Using user namespaces, normal user tasks can change
746  			 * their current->fs->root to point to arbitrary
747  			 * directories. Since the intention of the "only dump
748  			 * with a fully qualified path" rule is to control where
749  			 * coredumps may be placed using root privileges,
750  			 * current->fs->root must not be used. Instead, use the
751  			 * root directory of init_task.
752  			 */
753  			struct path root;
754  
755  			task_lock(&init_task);
756  			get_fs_root(init_task.fs, &root);
757  			task_unlock(&init_task);
758  			cprm.file = file_open_root(&root, cn.corename,
759  						   open_flags, 0600);
760  			path_put(&root);
761  		} else {
762  			cprm.file = filp_open(cn.corename, open_flags, 0600);
763  		}
764  		if (IS_ERR(cprm.file))
765  			goto fail_unlock;
766  
767  		inode = file_inode(cprm.file);
768  		if (inode->i_nlink > 1)
769  			goto close_fail;
770  		if (d_unhashed(cprm.file->f_path.dentry))
771  			goto close_fail;
772  		/*
773  		 * AK: actually i see no reason to not allow this for named
774  		 * pipes etc, but keep the previous behaviour for now.
775  		 */
776  		if (!S_ISREG(inode->i_mode))
777  			goto close_fail;
778  		/*
779  		 * Don't dump core if the filesystem changed owner or mode
780  		 * of the file during file creation. This is an issue when
781  		 * a process dumps core while its cwd is e.g. on a vfat
782  		 * filesystem.
783  		 */
784  		mnt_userns = file_mnt_user_ns(cprm.file);
785  		if (!uid_eq(i_uid_into_mnt(mnt_userns, inode), current_fsuid()))
786  			goto close_fail;
787  		if ((inode->i_mode & 0677) != 0600)
788  			goto close_fail;
789  		if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
790  			goto close_fail;
791  		if (do_truncate(mnt_userns, cprm.file->f_path.dentry,
792  				0, 0, cprm.file))
793  			goto close_fail;
794  	}
795  
796  	/* get us an unshared descriptor table; almost always a no-op */
797  	/* The cell spufs coredump code reads the file descriptor tables */
798  	retval = unshare_files();
799  	if (retval)
800  		goto close_fail;
801  	if (!dump_interrupted()) {
802  		/*
803  		 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
804  		 * have this set to NULL.
805  		 */
806  		if (!cprm.file) {
807  			pr_info("Core dump to |%s disabled\n", cn.corename);
808  			goto close_fail;
809  		}
810  		file_start_write(cprm.file);
811  		core_dumped = binfmt->core_dump(&cprm);
812  		/*
813  		 * Ensures that file size is big enough to contain the current
814  		 * file postion. This prevents gdb from complaining about
815  		 * a truncated file if the last "write" to the file was
816  		 * dump_skip.
817  		 */
818  		if (cprm.to_skip) {
819  			cprm.to_skip--;
820  			dump_emit(&cprm, "", 1);
821  		}
822  		file_end_write(cprm.file);
823  	}
824  	if (ispipe && core_pipe_limit)
825  		wait_for_dump_helpers(cprm.file);
826  close_fail:
827  	if (cprm.file)
828  		filp_close(cprm.file, NULL);
829  fail_dropcount:
830  	if (ispipe)
831  		atomic_dec(&core_dump_count);
832  fail_unlock:
833  	kfree(argv);
834  	kfree(cn.corename);
835  	coredump_finish(mm, core_dumped);
836  	revert_creds(old_cred);
837  fail_creds:
838  	put_cred(cred);
839  fail:
840  	return;
841  }
842  
843  /*
844   * Core dumping helper functions.  These are the only things you should
845   * do on a core-file: use only these functions to write out all the
846   * necessary info.
847   */
848  static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr)
849  {
850  	struct file *file = cprm->file;
851  	loff_t pos = file->f_pos;
852  	ssize_t n;
853  	if (cprm->written + nr > cprm->limit)
854  		return 0;
855  
856  
857  	if (dump_interrupted())
858  		return 0;
859  	n = __kernel_write(file, addr, nr, &pos);
860  	if (n != nr)
861  		return 0;
862  	file->f_pos = pos;
863  	cprm->written += n;
864  	cprm->pos += n;
865  
866  	return 1;
867  }
868  
869  static int __dump_skip(struct coredump_params *cprm, size_t nr)
870  {
871  	static char zeroes[PAGE_SIZE];
872  	struct file *file = cprm->file;
873  	if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
874  		if (dump_interrupted() ||
875  		    file->f_op->llseek(file, nr, SEEK_CUR) < 0)
876  			return 0;
877  		cprm->pos += nr;
878  		return 1;
879  	} else {
880  		while (nr > PAGE_SIZE) {
881  			if (!__dump_emit(cprm, zeroes, PAGE_SIZE))
882  				return 0;
883  			nr -= PAGE_SIZE;
884  		}
885  		return __dump_emit(cprm, zeroes, nr);
886  	}
887  }
888  
889  int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
890  {
891  	if (cprm->to_skip) {
892  		if (!__dump_skip(cprm, cprm->to_skip))
893  			return 0;
894  		cprm->to_skip = 0;
895  	}
896  	return __dump_emit(cprm, addr, nr);
897  }
898  EXPORT_SYMBOL(dump_emit);
899  
900  void dump_skip_to(struct coredump_params *cprm, unsigned long pos)
901  {
902  	cprm->to_skip = pos - cprm->pos;
903  }
904  EXPORT_SYMBOL(dump_skip_to);
905  
906  void dump_skip(struct coredump_params *cprm, size_t nr)
907  {
908  	cprm->to_skip += nr;
909  }
910  EXPORT_SYMBOL(dump_skip);
911  
912  #ifdef CONFIG_ELF_CORE
913  int dump_user_range(struct coredump_params *cprm, unsigned long start,
914  		    unsigned long len)
915  {
916  	unsigned long addr;
917  
918  	for (addr = start; addr < start + len; addr += PAGE_SIZE) {
919  		struct page *page;
920  		int stop;
921  
922  		/*
923  		 * To avoid having to allocate page tables for virtual address
924  		 * ranges that have never been used yet, and also to make it
925  		 * easy to generate sparse core files, use a helper that returns
926  		 * NULL when encountering an empty page table entry that would
927  		 * otherwise have been filled with the zero page.
928  		 */
929  		page = get_dump_page(addr);
930  		if (page) {
931  			void *kaddr = kmap_local_page(page);
932  
933  			stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
934  			kunmap_local(kaddr);
935  			put_page(page);
936  			if (stop)
937  				return 0;
938  		} else {
939  			dump_skip(cprm, PAGE_SIZE);
940  		}
941  	}
942  	return 1;
943  }
944  #endif
945  
946  int dump_align(struct coredump_params *cprm, int align)
947  {
948  	unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1);
949  	if (align & (align - 1))
950  		return 0;
951  	if (mod)
952  		cprm->to_skip += align - mod;
953  	return 1;
954  }
955  EXPORT_SYMBOL(dump_align);
956  
957  /*
958   * The purpose of always_dump_vma() is to make sure that special kernel mappings
959   * that are useful for post-mortem analysis are included in every core dump.
960   * In that way we ensure that the core dump is fully interpretable later
961   * without matching up the same kernel and hardware config to see what PC values
962   * meant. These special mappings include - vDSO, vsyscall, and other
963   * architecture specific mappings
964   */
965  static bool always_dump_vma(struct vm_area_struct *vma)
966  {
967  	/* Any vsyscall mappings? */
968  	if (vma == get_gate_vma(vma->vm_mm))
969  		return true;
970  
971  	/*
972  	 * Assume that all vmas with a .name op should always be dumped.
973  	 * If this changes, a new vm_ops field can easily be added.
974  	 */
975  	if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
976  		return true;
977  
978  	/*
979  	 * arch_vma_name() returns non-NULL for special architecture mappings,
980  	 * such as vDSO sections.
981  	 */
982  	if (arch_vma_name(vma))
983  		return true;
984  
985  	return false;
986  }
987  
988  /*
989   * Decide how much of @vma's contents should be included in a core dump.
990   */
991  static unsigned long vma_dump_size(struct vm_area_struct *vma,
992  				   unsigned long mm_flags)
993  {
994  #define FILTER(type)	(mm_flags & (1UL << MMF_DUMP_##type))
995  
996  	/* always dump the vdso and vsyscall sections */
997  	if (always_dump_vma(vma))
998  		goto whole;
999  
1000  	if (vma->vm_flags & VM_DONTDUMP)
1001  		return 0;
1002  
1003  	/* support for DAX */
1004  	if (vma_is_dax(vma)) {
1005  		if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
1006  			goto whole;
1007  		if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
1008  			goto whole;
1009  		return 0;
1010  	}
1011  
1012  	/* Hugetlb memory check */
1013  	if (is_vm_hugetlb_page(vma)) {
1014  		if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
1015  			goto whole;
1016  		if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
1017  			goto whole;
1018  		return 0;
1019  	}
1020  
1021  	/* Do not dump I/O mapped devices or special mappings */
1022  	if (vma->vm_flags & VM_IO)
1023  		return 0;
1024  
1025  	/* By default, dump shared memory if mapped from an anonymous file. */
1026  	if (vma->vm_flags & VM_SHARED) {
1027  		if (file_inode(vma->vm_file)->i_nlink == 0 ?
1028  		    FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
1029  			goto whole;
1030  		return 0;
1031  	}
1032  
1033  	/* Dump segments that have been written to.  */
1034  	if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
1035  		goto whole;
1036  	if (vma->vm_file == NULL)
1037  		return 0;
1038  
1039  	if (FILTER(MAPPED_PRIVATE))
1040  		goto whole;
1041  
1042  	/*
1043  	 * If this is the beginning of an executable file mapping,
1044  	 * dump the first page to aid in determining what was mapped here.
1045  	 */
1046  	if (FILTER(ELF_HEADERS) &&
1047  	    vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ) &&
1048  	    (READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
1049  		return PAGE_SIZE;
1050  
1051  #undef	FILTER
1052  
1053  	return 0;
1054  
1055  whole:
1056  	return vma->vm_end - vma->vm_start;
1057  }
1058  
1059  static struct vm_area_struct *first_vma(struct task_struct *tsk,
1060  					struct vm_area_struct *gate_vma)
1061  {
1062  	struct vm_area_struct *ret = tsk->mm->mmap;
1063  
1064  	if (ret)
1065  		return ret;
1066  	return gate_vma;
1067  }
1068  
1069  /*
1070   * Helper function for iterating across a vma list.  It ensures that the caller
1071   * will visit `gate_vma' prior to terminating the search.
1072   */
1073  static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
1074  				       struct vm_area_struct *gate_vma)
1075  {
1076  	struct vm_area_struct *ret;
1077  
1078  	ret = this_vma->vm_next;
1079  	if (ret)
1080  		return ret;
1081  	if (this_vma == gate_vma)
1082  		return NULL;
1083  	return gate_vma;
1084  }
1085  
1086  /*
1087   * Under the mmap_lock, take a snapshot of relevant information about the task's
1088   * VMAs.
1089   */
1090  int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
1091  		      struct core_vma_metadata **vma_meta,
1092  		      size_t *vma_data_size_ptr)
1093  {
1094  	struct vm_area_struct *vma, *gate_vma;
1095  	struct mm_struct *mm = current->mm;
1096  	int i;
1097  	size_t vma_data_size = 0;
1098  
1099  	/*
1100  	 * Once the stack expansion code is fixed to not change VMA bounds
1101  	 * under mmap_lock in read mode, this can be changed to take the
1102  	 * mmap_lock in read mode.
1103  	 */
1104  	if (mmap_write_lock_killable(mm))
1105  		return -EINTR;
1106  
1107  	gate_vma = get_gate_vma(mm);
1108  	*vma_count = mm->map_count + (gate_vma ? 1 : 0);
1109  
1110  	*vma_meta = kvmalloc_array(*vma_count, sizeof(**vma_meta), GFP_KERNEL);
1111  	if (!*vma_meta) {
1112  		mmap_write_unlock(mm);
1113  		return -ENOMEM;
1114  	}
1115  
1116  	for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
1117  			vma = next_vma(vma, gate_vma), i++) {
1118  		struct core_vma_metadata *m = (*vma_meta) + i;
1119  
1120  		m->start = vma->vm_start;
1121  		m->end = vma->vm_end;
1122  		m->flags = vma->vm_flags;
1123  		m->dump_size = vma_dump_size(vma, cprm->mm_flags);
1124  
1125  		vma_data_size += m->dump_size;
1126  	}
1127  
1128  	mmap_write_unlock(mm);
1129  
1130  	if (WARN_ON(i != *vma_count))
1131  		return -EFAULT;
1132  
1133  	*vma_data_size_ptr = vma_data_size;
1134  	return 0;
1135  }
1136