[mirror_ubuntu-bionic-kernel.git] / fs / notify / fanotify / fanotify.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/fanotify.h>
#include <linux/fdtable.h>
#include <linux/fsnotify_backend.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/kernel.h> /* UINT_MAX */
#include <linux/mount.h>
#include <linux/sched.h>
#include <linux/sched/user.h>
#include <linux/types.h>
#include <linux/wait.h>
#include <linux/audit.h>

#include "fanotify.h"

static bool should_merge(struct fsnotify_event *old_fsn,
			 struct fsnotify_event *new_fsn)
{
	struct fanotify_event_info *old, *new;

	pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn);
	old = FANOTIFY_E(old_fsn);
	new = FANOTIFY_E(new_fsn);

	if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid &&
	    old->path.mnt == new->path.mnt &&
	    old->path.dentry == new->path.dentry)
		return true;
	return false;
}

/* and the list better be locked by something too! */
static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
{
	struct fsnotify_event *test_event;

	pr_debug("%s: list=%p event=%p\n", __func__, list, event);

	/*
	 * Don't merge a permission event with any other event so that we know
	 * the event structure we have created in fanotify_handle_event() is the
	 * one we should check for permission response.
	 */
	if (fanotify_is_perm_event(event->mask))
		return 0;

	list_for_each_entry_reverse(test_event, list, list) {
		if (should_merge(test_event, event)) {
			test_event->mask |= event->mask;
			return 1;
		}
	}

	return 0;
}

static int fanotify_get_response(struct fsnotify_group *group,
				 struct fanotify_perm_event_info *event,
				 struct fsnotify_iter_info *iter_info)
{
	int ret;

	pr_debug("%s: group=%p event=%p\n", __func__, group, event);

	wait_event(group->fanotify_data.access_waitq, event->response);

	/* userspace responded, convert to something usable */
	switch (event->response & ~FAN_AUDIT) {
	case FAN_ALLOW:
		ret = 0;
		break;
	case FAN_DENY:
	default:
		ret = -EPERM;
	}

	/* Check if the response should be audited */
	if (event->response & FAN_AUDIT)
		audit_fanotify(event->response & ~FAN_AUDIT);

	event->response = 0;

	pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
		 group, event, ret);
	
	return ret;
}

static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark,
				       struct fsnotify_mark *vfsmnt_mark,
				       u32 event_mask,
				       const void *data, int data_type)
{
	__u32 marks_mask = 0, marks_ignored_mask = 0;
	const struct path *path = data;

	pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p"
		 " data_type=%d\n", __func__, inode_mark, vfsmnt_mark,
		 event_mask, data, data_type);

	/* if we don't have enough info to send an event to userspace say no */
	if (data_type != FSNOTIFY_EVENT_PATH)
		return false;

	/* sorry, fanotify only gives a damn about files and dirs */
	if (!d_is_reg(path->dentry) &&
	    !d_can_lookup(path->dentry))
		return false;

	/*
	 * if the event is for a child and this inode doesn't care about
	 * events on the child, don't send it!
	 */
	if (inode_mark &&
	    (!(event_mask & FS_EVENT_ON_CHILD) ||
	     (inode_mark->mask & FS_EVENT_ON_CHILD))) {
		marks_mask |= inode_mark->mask;
		marks_ignored_mask |= inode_mark->ignored_mask;
	}

	if (vfsmnt_mark) {
		marks_mask |= vfsmnt_mark->mask;
		marks_ignored_mask |= vfsmnt_mark->ignored_mask;
	}

	if (d_is_dir(path->dentry) &&
	    !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
		return false;

	if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask &
				 ~marks_ignored_mask)
		return true;

	return false;
}

struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask,
						 const struct path *path)
{
	struct fanotify_event_info *event;

	if (fanotify_is_perm_event(mask)) {
		struct fanotify_perm_event_info *pevent;

		pevent = kmem_cache_alloc(fanotify_perm_event_cachep,
					  GFP_KERNEL);
		if (!pevent)
			return NULL;
		event = &pevent->fae;
		pevent->response = 0;
		goto init;
	}
	event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
	if (!event)
		return NULL;
init: __maybe_unused
	fsnotify_init_event(&event->fse, inode, mask);
	event->tgid = get_pid(task_tgid(current));
	if (path) {
		event->path = *path;
		path_get(&event->path);
	} else {
		event->path.mnt = NULL;
		event->path.dentry = NULL;
	}
	return event;
}

static int fanotify_handle_event(struct fsnotify_group *group,
				 struct inode *inode,
				 struct fsnotify_mark *inode_mark,
				 struct fsnotify_mark *fanotify_mark,
				 u32 mask, const void *data, int data_type,
				 const unsigned char *file_name, u32 cookie,
				 struct fsnotify_iter_info *iter_info)
{
	int ret = 0;
	struct fanotify_event_info *event;
	struct fsnotify_event *fsn_event;

	BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
	BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
	BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
	BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
	BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
	BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
	BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
	BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);

	if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data,
					data_type))
		return 0;

	pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
		 mask);

	if (fanotify_is_perm_event(mask)) {
		/*
		 * fsnotify_prepare_user_wait() fails if we race with mark
		 * deletion.  Just let the operation pass in that case.
		 */
		if (!fsnotify_prepare_user_wait(iter_info))
			return 0;
	}

	event = fanotify_alloc_event(inode, mask, data);
	ret = -ENOMEM;
	if (unlikely(!event))
		goto finish;

	fsn_event = &event->fse;
	ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
	if (ret) {
		/* Permission events shouldn't be merged */
		BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS);
		/* Our event wasn't used in the end. Free it. */
		fsnotify_destroy_event(group, fsn_event);

		ret = 0;
	} else if (fanotify_is_perm_event(mask)) {
		ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event),
					    iter_info);
		fsnotify_destroy_event(group, fsn_event);
	}
finish:
	if (fanotify_is_perm_event(mask))
		fsnotify_finish_user_wait(iter_info);

	return ret;
}

static void fanotify_free_group_priv(struct fsnotify_group *group)
{
	struct user_struct *user;

	user = group->fanotify_data.user;
	atomic_dec(&user->fanotify_listeners);
	free_uid(user);
}

static void fanotify_free_event(struct fsnotify_event *fsn_event)
{
	struct fanotify_event_info *event;

	event = FANOTIFY_E(fsn_event);
	path_put(&event->path);
	put_pid(event->tgid);
	if (fanotify_is_perm_event(fsn_event->mask)) {
		kmem_cache_free(fanotify_perm_event_cachep,
				FANOTIFY_PE(fsn_event));
		return;
	}
	kmem_cache_free(fanotify_event_cachep, event);
}

static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
{
	kmem_cache_free(fanotify_mark_cache, fsn_mark);
}

const struct fsnotify_ops fanotify_fsnotify_ops = {
	.handle_event = fanotify_handle_event,
	.free_group_priv = fanotify_free_group_priv,
	.free_event = fanotify_free_event,
	.free_mark = fanotify_free_mark,
};
Commit	Line	Data
	1	// SPDX-License-Identifier: GPL-2.0
	2	#include <linux/fanotify.h>
	3	#include <linux/fdtable.h>
	4	#include <linux/fsnotify_backend.h>
	5	#include <linux/init.h>
	6	#include <linux/jiffies.h>
	7	#include <linux/kernel.h> /* UINT_MAX */
	8	#include <linux/mount.h>
	9	#include <linux/sched.h>
	10	#include <linux/sched/user.h>
	11	#include <linux/types.h>
	12	#include <linux/wait.h>
	13	#include <linux/audit.h>
	14
	15	#include "fanotify.h"
	16
	17	static bool should_merge(struct fsnotify_event *old_fsn,
	18	struct fsnotify_event *new_fsn)
	19	{
	20	struct fanotify_event_info old, new;
	21
	22	pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn);
	23	old = FANOTIFY_E(old_fsn);
	24	new = FANOTIFY_E(new_fsn);
	25
	26	if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid &&
	27	old->path.mnt == new->path.mnt &&
	28	old->path.dentry == new->path.dentry)
	29	return true;
	30	return false;
	31	}
	32
	33	/* and the list better be locked by something too! */
	34	static int fanotify_merge(struct list_head list, struct fsnotify_event event)
	35	{
	36	struct fsnotify_event *test_event;
	37
	38	pr_debug("%s: list=%p event=%p\n", __func__, list, event);
	39
	40	/*
	41	* Don't merge a permission event with any other event so that we know
	42	* the event structure we have created in fanotify_handle_event() is the
	43	* one we should check for permission response.
	44	*/
	45	if (fanotify_is_perm_event(event->mask))
	46	return 0;
	47
	48	list_for_each_entry_reverse(test_event, list, list) {
	49	if (should_merge(test_event, event)) {
	50	test_event->mask \|= event->mask;
	51	return 1;
	52	}
	53	}
	54
	55	return 0;
	56	}
	57
	58	static int fanotify_get_response(struct fsnotify_group *group,
	59	struct fanotify_perm_event_info *event,
	60	struct fsnotify_iter_info *iter_info)
	61	{
	62	int ret;
	63
	64	pr_debug("%s: group=%p event=%p\n", __func__, group, event);
	65
	66	wait_event(group->fanotify_data.access_waitq, event->response);
	67
	68	/* userspace responded, convert to something usable */
	69	switch (event->response & ~FAN_AUDIT) {
	70	case FAN_ALLOW:
	71	ret = 0;
	72	break;
	73	case FAN_DENY:
	74	default:
	75	ret = -EPERM;
	76	}
	77
	78	/* Check if the response should be audited */
	79	if (event->response & FAN_AUDIT)
	80	audit_fanotify(event->response & ~FAN_AUDIT);
	81
	82	event->response = 0;
	83
	84	pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
	85	group, event, ret);
	86
	87	return ret;
	88	}
	89
	90	static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark,
	91	struct fsnotify_mark *vfsmnt_mark,
	92	u32 event_mask,
	93	const void *data, int data_type)
	94	{
	95	__u32 marks_mask = 0, marks_ignored_mask = 0;
	96	const struct path *path = data;
	97
	98	pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p"
	99	" data_type=%d\n", __func__, inode_mark, vfsmnt_mark,
	100	event_mask, data, data_type);
	101
	102	/* if we don't have enough info to send an event to userspace say no */
	103	if (data_type != FSNOTIFY_EVENT_PATH)
	104	return false;
	105
	106	/* sorry, fanotify only gives a damn about files and dirs */
	107	if (!d_is_reg(path->dentry) &&
	108	!d_can_lookup(path->dentry))
	109	return false;
	110
	111	/*
	112	* if the event is for a child and this inode doesn't care about
	113	* events on the child, don't send it!
	114	*/
	115	if (inode_mark &&
	116	(!(event_mask & FS_EVENT_ON_CHILD) \|\|
	117	(inode_mark->mask & FS_EVENT_ON_CHILD))) {
	118	marks_mask \|= inode_mark->mask;
	119	marks_ignored_mask \|= inode_mark->ignored_mask;
	120	}
	121
	122	if (vfsmnt_mark) {
	123	marks_mask \|= vfsmnt_mark->mask;
	124	marks_ignored_mask \|= vfsmnt_mark->ignored_mask;
	125	}
	126
	127	if (d_is_dir(path->dentry) &&
	128	!(marks_mask & FS_ISDIR & ~marks_ignored_mask))
	129	return false;
	130
	131	if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask &
	132	~marks_ignored_mask)
	133	return true;
	134
	135	return false;
	136	}
	137
	138	struct fanotify_event_info fanotify_alloc_event(struct inode inode, u32 mask,
	139	const struct path *path)
	140	{
	141	struct fanotify_event_info *event;
	142
	143	if (fanotify_is_perm_event(mask)) {
	144	struct fanotify_perm_event_info *pevent;
	145
	146	pevent = kmem_cache_alloc(fanotify_perm_event_cachep,
	147	GFP_KERNEL);
	148	if (!pevent)
	149	return NULL;
	150	event = &pevent->fae;
	151	pevent->response = 0;
	152	goto init;
	153	}
	154	event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
	155	if (!event)
	156	return NULL;
	157	init: __maybe_unused
	158	fsnotify_init_event(&event->fse, inode, mask);
	159	event->tgid = get_pid(task_tgid(current));
	160	if (path) {
	161	event->path = *path;
	162	path_get(&event->path);
	163	} else {
	164	event->path.mnt = NULL;
	165	event->path.dentry = NULL;
	166	}
	167	return event;
	168	}
	169
	170	static int fanotify_handle_event(struct fsnotify_group *group,
	171	struct inode *inode,
	172	struct fsnotify_mark *inode_mark,
	173	struct fsnotify_mark *fanotify_mark,
	174	u32 mask, const void *data, int data_type,
	175	const unsigned char *file_name, u32 cookie,
	176	struct fsnotify_iter_info *iter_info)
	177	{
	178	int ret = 0;
	179	struct fanotify_event_info *event;
	180	struct fsnotify_event *fsn_event;
	181
	182	BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
	183	BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
	184	BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
	185	BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
	186	BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
	187	BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
	188	BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
	189	BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
	190	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
	191	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
	192
	193	if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data,
	194	data_type))
	195	return 0;
	196
	197	pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
	198	mask);
	199
	200	if (fanotify_is_perm_event(mask)) {
	201	/*
	202	* fsnotify_prepare_user_wait() fails if we race with mark
	203	* deletion. Just let the operation pass in that case.
	204	*/
	205	if (!fsnotify_prepare_user_wait(iter_info))
	206	return 0;
	207	}
	208
	209	event = fanotify_alloc_event(inode, mask, data);
	210	ret = -ENOMEM;
	211	if (unlikely(!event))
	212	goto finish;
	213
	214	fsn_event = &event->fse;
	215	ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
	216	if (ret) {
	217	/* Permission events shouldn't be merged */
	218	BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS);
	219	/* Our event wasn't used in the end. Free it. */
	220	fsnotify_destroy_event(group, fsn_event);
	221
	222	ret = 0;
	223	} else if (fanotify_is_perm_event(mask)) {
	224	ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event),
	225	iter_info);
	226	fsnotify_destroy_event(group, fsn_event);
	227	}
	228	finish:
	229	if (fanotify_is_perm_event(mask))
	230	fsnotify_finish_user_wait(iter_info);
	231
	232	return ret;
	233	}
	234
	235	static void fanotify_free_group_priv(struct fsnotify_group *group)
	236	{
	237	struct user_struct *user;
	238
	239	user = group->fanotify_data.user;
	240	atomic_dec(&user->fanotify_listeners);
	241	free_uid(user);
	242	}
	243
	244	static void fanotify_free_event(struct fsnotify_event *fsn_event)
	245	{
	246	struct fanotify_event_info *event;
	247
	248	event = FANOTIFY_E(fsn_event);
	249	path_put(&event->path);
	250	put_pid(event->tgid);
	251	if (fanotify_is_perm_event(fsn_event->mask)) {
	252	kmem_cache_free(fanotify_perm_event_cachep,
	253	FANOTIFY_PE(fsn_event));
	254	return;
	255	}
	256	kmem_cache_free(fanotify_event_cachep, event);
	257	}
	258
	259	static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
	260	{
	261	kmem_cache_free(fanotify_mark_cache, fsn_mark);
	262	}
	263
	264	const struct fsnotify_ops fanotify_fsnotify_ops = {
	265	.handle_event = fanotify_handle_event,
	266	.free_group_priv = fanotify_free_group_priv,
	267	.free_event = fanotify_free_event,
	268	.free_mark = fanotify_free_mark,
	269	};