fs/notify/fanotify/fanotify.c - linux - Git at Google

 // 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/sched/signal.h>
 #include <linux/types.h>
 #include <linux/wait.h>
 #include <linux/audit.h>
 #include <linux/sched/mm.h>
 #include <linux/statfs.h>

 #include "fanotify.h"

 static bool should_merge(struct fsnotify_event *old_fsn,
 			 struct fsnotify_event *new_fsn)
 {
 	struct fanotify_event *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->pid != new->pid ||
 	    old->fh_type != new->fh_type || old->fh_len != new->fh_len)
 		return false;

 	if (fanotify_event_has_path(old)) {
 		return old->path.mnt == new->path.mnt &&
 			old->path.dentry == new->path.dentry;
 	} else if (fanotify_event_has_fid(old)) {
 		/*
 		 * We want to merge many dirent events in the same dir (i.e.
 		 * creates/unlinks/renames), but we do not want to merge dirent
 		 * events referring to subdirs with dirent events referring to
 		 * non subdirs, otherwise, user won't be able to tell from a
 		 * mask FAN_CREATE|FAN_DELETE|FAN_ONDIR if it describes mkdir+
 		 * unlink pair or rmdir+create pair of events.
 		 */
 		return (old->mask & FS_ISDIR) == (new->mask & FS_ISDIR) &&
 			fanotify_fid_equal(&old->fid, &new->fid, old->fh_len);
 	}

 	/* Do not merge events if we failed to encode fid */
 	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;
 	struct fanotify_event *new;

 	pr_debug("%s: list=%p event=%p\n", __func__, list, event);
 	new = FANOTIFY_E(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(new->mask))
 		return 0;

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

 	return 0;
 }

 /*
  * Wait for response to permission event. The function also takes care of
  * freeing the permission event (or offloads that in case the wait is canceled
  * by a signal). The function returns 0 in case access got allowed by userspace,
  * -EPERM in case userspace disallowed the access, and -ERESTARTSYS in case
  * the wait got interrupted by a signal.
  */
 static int fanotify_get_response(struct fsnotify_group *group,
 				 struct fanotify_perm_event *event,
 				 struct fsnotify_iter_info *iter_info)
 {
 	int ret;

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

 	ret = wait_event_killable(group->fanotify_data.access_waitq,
 				  event->state == FAN_EVENT_ANSWERED);
 	/* Signal pending? */
 	if (ret < 0) {
 		spin_lock(&group->notification_lock);
 		/* Event reported to userspace and no answer yet? */
 		if (event->state == FAN_EVENT_REPORTED) {
 			/* Event will get freed once userspace answers to it */
 			event->state = FAN_EVENT_CANCELED;
 			spin_unlock(&group->notification_lock);
 			return ret;
 		}
 		/* Event not yet reported? Just remove it. */
 		if (event->state == FAN_EVENT_INIT)
 			fsnotify_remove_queued_event(group, &event->fae.fse);
 		/*
 		 * Event may be also answered in case signal delivery raced
 		 * with wakeup. In that case we have nothing to do besides
 		 * freeing the event and reporting error.
 		 */
 		spin_unlock(&group->notification_lock);
 		goto out;
 	}

 	/* 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);

 	pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
 		 group, event, ret);
 out:
 	fsnotify_destroy_event(group, &event->fae.fse);

 	return ret;
 }

 /*
  * This function returns a mask for an event that only contains the flags
  * that have been specifically requested by the user. Flags that may have
  * been included within the event mask, but have not been explicitly
  * requested by the user, will not be present in the returned mask.
  */
 static u32 fanotify_group_event_mask(struct fsnotify_group *group,
 				     struct fsnotify_iter_info *iter_info,
 				     u32 event_mask, const void *data,
 				     int data_type)
 {
 	__u32 marks_mask = 0, marks_ignored_mask = 0;
 	__u32 test_mask, user_mask = FANOTIFY_OUTGOING_EVENTS;
 	const struct path *path = data;
 	struct fsnotify_mark *mark;
 	int type;

 	pr_debug("%s: report_mask=%x mask=%x data=%p data_type=%d\n",
 		 __func__, iter_info->report_mask, event_mask, data, data_type);

 	if (!FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
 		/* Do we have path to open a file descriptor? */
 		if (data_type != FSNOTIFY_EVENT_PATH)
 			return 0;
 		/* Path type events are only relevant for files and dirs */
 		if (!d_is_reg(path->dentry) && !d_can_lookup(path->dentry))
 			return 0;
 	}

 	fsnotify_foreach_obj_type(type) {
 		if (!fsnotify_iter_should_report_type(iter_info, type))
 			continue;
 		mark = iter_info->marks[type];
 		/*
 		 * If the event is for a child and this mark doesn't care about
 		 * events on a child, don't send it!
 		 */
 		if (event_mask & FS_EVENT_ON_CHILD &&
 		    (type != FSNOTIFY_OBJ_TYPE_INODE ||
 		     !(mark->mask & FS_EVENT_ON_CHILD)))
 			continue;

 		marks_mask |= mark->mask;
 		marks_ignored_mask |= mark->ignored_mask;
 	}

 	test_mask = event_mask & marks_mask & ~marks_ignored_mask;

 	/*
 	 * dirent modification events (create/delete/move) do not carry the
 	 * child entry name/inode information. Instead, we report FAN_ONDIR
 	 * for mkdir/rmdir so user can differentiate them from creat/unlink.
 	 *
 	 * For backward compatibility and consistency, do not report FAN_ONDIR
 	 * to user in legacy fanotify mode (reporting fd) and report FAN_ONDIR
 	 * to user in FAN_REPORT_FID mode for all event types.
 	 */
 	if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
 		/* Do not report FAN_ONDIR without any event */
 		if (!(test_mask & ~FAN_ONDIR))
 			return 0;
 	} else {
 		user_mask &= ~FAN_ONDIR;
 	}

 	if (event_mask & FS_ISDIR &&
 	    !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
 		return 0;

 	return test_mask & user_mask;
 }

 static int fanotify_encode_fid(struct fanotify_event *event,
 			       struct inode *inode, gfp_t gfp,
 			       __kernel_fsid_t *fsid)
 {
 	struct fanotify_fid *fid = &event->fid;
 	int dwords, bytes = 0;
 	int err, type;

 	fid->ext_fh = NULL;
 	dwords = 0;
 	err = -ENOENT;
 	type = exportfs_encode_inode_fh(inode, NULL, &dwords, NULL);
 	if (!dwords)
 		goto out_err;

 	bytes = dwords << 2;
 	if (bytes > FANOTIFY_INLINE_FH_LEN) {
 		/* Treat failure to allocate fh as failure to allocate event */
 		err = -ENOMEM;
 		fid->ext_fh = kmalloc(bytes, gfp);
 		if (!fid->ext_fh)
 			goto out_err;
 	}

 	type = exportfs_encode_inode_fh(inode, fanotify_fid_fh(fid, bytes),
 					&dwords, NULL);
 	err = -EINVAL;
 	if (!type || type == FILEID_INVALID || bytes != dwords << 2)
 		goto out_err;

 	fid->fsid = *fsid;
 	event->fh_len = bytes;

 	return type;

 out_err:
 	pr_warn_ratelimited("fanotify: failed to encode fid (fsid=%x.%x, "
 			    "type=%d, bytes=%d, err=%i)\n",
 			    fsid->val[0], fsid->val[1], type, bytes, err);
 	kfree(fid->ext_fh);
 	fid->ext_fh = NULL;
 	event->fh_len = 0;

 	return FILEID_INVALID;
 }

 /*
  * The inode to use as identifier when reporting fid depends on the event.
  * Report the modified directory inode on dirent modification events.
  * Report the "victim" inode otherwise.
  * For example:
  * FS_ATTRIB reports the child inode even if reported on a watched parent.
  * FS_CREATE reports the modified dir inode and not the created inode.
  */
 static struct inode *fanotify_fid_inode(struct inode *to_tell, u32 event_mask,
 					const void *data, int data_type)
 {
 	if (event_mask & ALL_FSNOTIFY_DIRENT_EVENTS)
 		return to_tell;
 	else if (data_type == FSNOTIFY_EVENT_INODE)
 		return (struct inode *)data;
 	else if (data_type == FSNOTIFY_EVENT_PATH)
 		return d_inode(((struct path *)data)->dentry);
 	return NULL;
 }

 struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
 					    struct inode *inode, u32 mask,
 					    const void *data, int data_type,
 					    __kernel_fsid_t *fsid)
 {
 	struct fanotify_event *event = NULL;
 	gfp_t gfp = GFP_KERNEL_ACCOUNT;
 	struct inode *id = fanotify_fid_inode(inode, mask, data, data_type);

 	/*
 	 * For queues with unlimited length lost events are not expected and
 	 * can possibly have security implications. Avoid losing events when
 	 * memory is short.
 	 */
 	if (group->max_events == UINT_MAX)
 		gfp |= __GFP_NOFAIL;

 	/* Whoever is interested in the event, pays for the allocation. */
 	memalloc_use_memcg(group->memcg);

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

 		pevent = kmem_cache_alloc(fanotify_perm_event_cachep, gfp);
 		if (!pevent)
 			goto out;
 		event = &pevent->fae;
 		pevent->response = 0;
 		pevent->state = FAN_EVENT_INIT;
 		goto init;
 	}
 	event = kmem_cache_alloc(fanotify_event_cachep, gfp);
 	if (!event)
 		goto out;
 init: __maybe_unused
 	fsnotify_init_event(&event->fse, inode);
 	event->mask = mask;
 	if (FAN_GROUP_FLAG(group, FAN_REPORT_TID))
 		event->pid = get_pid(task_pid(current));
 	else
 		event->pid = get_pid(task_tgid(current));
 	event->fh_len = 0;
 	if (id && FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
 		/* Report the event without a file identifier on encode error */
 		event->fh_type = fanotify_encode_fid(event, id, gfp, fsid);
 	} else if (data_type == FSNOTIFY_EVENT_PATH) {
 		event->fh_type = FILEID_ROOT;
 		event->path = *((struct path *)data);
 		path_get(&event->path);
 	} else {
 		event->fh_type = FILEID_INVALID;
 		event->path.mnt = NULL;
 		event->path.dentry = NULL;
 	}
 out:
 	memalloc_unuse_memcg();
 	return event;
 }

 /*
  * Get cached fsid of the filesystem containing the object from any connector.
  * All connectors are supposed to have the same fsid, but we do not verify that
  * here.
  */
 static __kernel_fsid_t fanotify_get_fsid(struct fsnotify_iter_info *iter_info)
 {
 	int type;
 	__kernel_fsid_t fsid = {};

 	fsnotify_foreach_obj_type(type) {
 		struct fsnotify_mark_connector *conn;

 		if (!fsnotify_iter_should_report_type(iter_info, type))
 			continue;

 		conn = READ_ONCE(iter_info->marks[type]->connector);
 		/* Mark is just getting destroyed or created? */
 		if (!conn)
 			continue;
 		fsid = conn->fsid;
 		if (WARN_ON_ONCE(!fsid.val[0] && !fsid.val[1]))
 			continue;
 		return fsid;
 	}

 	return fsid;
 }

 static int fanotify_handle_event(struct fsnotify_group *group,
 				 struct inode *inode,
 				 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 *event;
 	struct fsnotify_event *fsn_event;
 	__kernel_fsid_t fsid = {};

 	BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
 	BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
 	BUILD_BUG_ON(FAN_ATTRIB != FS_ATTRIB);
 	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_MOVED_TO != FS_MOVED_TO);
 	BUILD_BUG_ON(FAN_MOVED_FROM != FS_MOVED_FROM);
 	BUILD_BUG_ON(FAN_CREATE != FS_CREATE);
 	BUILD_BUG_ON(FAN_DELETE != FS_DELETE);
 	BUILD_BUG_ON(FAN_DELETE_SELF != FS_DELETE_SELF);
 	BUILD_BUG_ON(FAN_MOVE_SELF != FS_MOVE_SELF);
 	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);
 	BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
 	BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);

 	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 19);

 	mask = fanotify_group_event_mask(group, iter_info, mask, data,
 					 data_type);
 	if (!mask)
 		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;
 	}

 	if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
 		fsid = fanotify_get_fsid(iter_info);
 		/* Racing with mark destruction or creation? */
 		if (!fsid.val[0] && !fsid.val[1])
 			return 0;
 	}

 	event = fanotify_alloc_event(group, inode, mask, data, data_type,
 				     &fsid);
 	ret = -ENOMEM;
 	if (unlikely(!event)) {
 		/*
 		 * We don't queue overflow events for permission events as
 		 * there the access is denied and so no event is in fact lost.
 		 */
 		if (!fanotify_is_perm_event(mask))
 			fsnotify_queue_overflow(group);
 		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 & FANOTIFY_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);
 	}
 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 *event;

 	event = FANOTIFY_E(fsn_event);
 	if (fanotify_event_has_path(event))
 		path_put(&event->path);
 	else if (fanotify_event_has_ext_fh(event))
 		kfree(event->fid.ext_fh);
 	put_pid(event->pid);
 	if (fanotify_is_perm_event(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,
 };
	// 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/sched/signal.h>
	#include <linux/types.h>
	#include <linux/wait.h>
	#include <linux/audit.h>
	#include <linux/sched/mm.h>
	#include <linux/statfs.h>

	#include "fanotify.h"

	static bool should_merge(struct fsnotify_event *old_fsn,
	struct fsnotify_event *new_fsn)
	{
	struct fanotify_event 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->pid != new->pid \|\|
	old->fh_type != new->fh_type \|\| old->fh_len != new->fh_len)
	return false;

	if (fanotify_event_has_path(old)) {
	return old->path.mnt == new->path.mnt &&
	old->path.dentry == new->path.dentry;
	} else if (fanotify_event_has_fid(old)) {
	/*
	* We want to merge many dirent events in the same dir (i.e.
	* creates/unlinks/renames), but we do not want to merge dirent
	* events referring to subdirs with dirent events referring to
	* non subdirs, otherwise, user won't be able to tell from a
	* mask FAN_CREATE\|FAN_DELETE\|FAN_ONDIR if it describes mkdir+
	* unlink pair or rmdir+create pair of events.
	*/
	return (old->mask & FS_ISDIR) == (new->mask & FS_ISDIR) &&
	fanotify_fid_equal(&old->fid, &new->fid, old->fh_len);
	}

	/* Do not merge events if we failed to encode fid */
	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;
	struct fanotify_event *new;

	pr_debug("%s: list=%p event=%p\n", __func__, list, event);
	new = FANOTIFY_E(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(new->mask))
	return 0;

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

	return 0;
	}

	/*
	* Wait for response to permission event. The function also takes care of
	* freeing the permission event (or offloads that in case the wait is canceled
	* by a signal). The function returns 0 in case access got allowed by userspace,
	* -EPERM in case userspace disallowed the access, and -ERESTARTSYS in case
	* the wait got interrupted by a signal.
	*/
	static int fanotify_get_response(struct fsnotify_group *group,
	struct fanotify_perm_event *event,
	struct fsnotify_iter_info *iter_info)
	{
	int ret;

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

	ret = wait_event_killable(group->fanotify_data.access_waitq,
	event->state == FAN_EVENT_ANSWERED);
	/* Signal pending? */
	if (ret < 0) {
	spin_lock(&group->notification_lock);
	/* Event reported to userspace and no answer yet? */
	if (event->state == FAN_EVENT_REPORTED) {
	/* Event will get freed once userspace answers to it */
	event->state = FAN_EVENT_CANCELED;
	spin_unlock(&group->notification_lock);
	return ret;
	}
	/* Event not yet reported? Just remove it. */
	if (event->state == FAN_EVENT_INIT)
	fsnotify_remove_queued_event(group, &event->fae.fse);
	/*
	* Event may be also answered in case signal delivery raced
	* with wakeup. In that case we have nothing to do besides
	* freeing the event and reporting error.
	*/
	spin_unlock(&group->notification_lock);
	goto out;
	}

	/* 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);

	pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
	group, event, ret);
	out:
	fsnotify_destroy_event(group, &event->fae.fse);

	return ret;
	}

	/*
	* This function returns a mask for an event that only contains the flags
	* that have been specifically requested by the user. Flags that may have
	* been included within the event mask, but have not been explicitly
	* requested by the user, will not be present in the returned mask.
	*/
	static u32 fanotify_group_event_mask(struct fsnotify_group *group,
	struct fsnotify_iter_info *iter_info,
	u32 event_mask, const void *data,
	int data_type)
	{
	__u32 marks_mask = 0, marks_ignored_mask = 0;
	__u32 test_mask, user_mask = FANOTIFY_OUTGOING_EVENTS;
	const struct path *path = data;
	struct fsnotify_mark *mark;
	int type;

	pr_debug("%s: report_mask=%x mask=%x data=%p data_type=%d\n",
	__func__, iter_info->report_mask, event_mask, data, data_type);

	if (!FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
	/* Do we have path to open a file descriptor? */
	if (data_type != FSNOTIFY_EVENT_PATH)
	return 0;
	/* Path type events are only relevant for files and dirs */
	if (!d_is_reg(path->dentry) && !d_can_lookup(path->dentry))
	return 0;
	}

	fsnotify_foreach_obj_type(type) {
	if (!fsnotify_iter_should_report_type(iter_info, type))
	continue;
	mark = iter_info->marks[type];
	/*
	* If the event is for a child and this mark doesn't care about
	* events on a child, don't send it!
	*/
	if (event_mask & FS_EVENT_ON_CHILD &&
	(type != FSNOTIFY_OBJ_TYPE_INODE \|\|
	!(mark->mask & FS_EVENT_ON_CHILD)))
	continue;

	marks_mask \|= mark->mask;
	marks_ignored_mask \|= mark->ignored_mask;
	}

	test_mask = event_mask & marks_mask & ~marks_ignored_mask;

	/*
	* dirent modification events (create/delete/move) do not carry the
	* child entry name/inode information. Instead, we report FAN_ONDIR
	* for mkdir/rmdir so user can differentiate them from creat/unlink.
	*
	* For backward compatibility and consistency, do not report FAN_ONDIR
	* to user in legacy fanotify mode (reporting fd) and report FAN_ONDIR
	* to user in FAN_REPORT_FID mode for all event types.
	*/
	if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
	/* Do not report FAN_ONDIR without any event */
	if (!(test_mask & ~FAN_ONDIR))
	return 0;
	} else {
	user_mask &= ~FAN_ONDIR;
	}

	if (event_mask & FS_ISDIR &&
	!(marks_mask & FS_ISDIR & ~marks_ignored_mask))
	return 0;

	return test_mask & user_mask;
	}

	static int fanotify_encode_fid(struct fanotify_event *event,
	struct inode *inode, gfp_t gfp,
	__kernel_fsid_t *fsid)
	{
	struct fanotify_fid *fid = &event->fid;
	int dwords, bytes = 0;
	int err, type;

	fid->ext_fh = NULL;
	dwords = 0;
	err = -ENOENT;
	type = exportfs_encode_inode_fh(inode, NULL, &dwords, NULL);
	if (!dwords)
	goto out_err;

	bytes = dwords << 2;
	if (bytes > FANOTIFY_INLINE_FH_LEN) {
	/* Treat failure to allocate fh as failure to allocate event */
	err = -ENOMEM;
	fid->ext_fh = kmalloc(bytes, gfp);
	if (!fid->ext_fh)
	goto out_err;
	}

	type = exportfs_encode_inode_fh(inode, fanotify_fid_fh(fid, bytes),
	&dwords, NULL);
	err = -EINVAL;
	if (!type \|\| type == FILEID_INVALID \|\| bytes != dwords << 2)
	goto out_err;

	fid->fsid = *fsid;
	event->fh_len = bytes;

	return type;

	out_err:
	pr_warn_ratelimited("fanotify: failed to encode fid (fsid=%x.%x, "
	"type=%d, bytes=%d, err=%i)\n",
	fsid->val[0], fsid->val[1], type, bytes, err);
	kfree(fid->ext_fh);
	fid->ext_fh = NULL;
	event->fh_len = 0;

	return FILEID_INVALID;
	}

	/*
	* The inode to use as identifier when reporting fid depends on the event.
	* Report the modified directory inode on dirent modification events.
	* Report the "victim" inode otherwise.
	* For example:
	* FS_ATTRIB reports the child inode even if reported on a watched parent.
	* FS_CREATE reports the modified dir inode and not the created inode.
	*/
	static struct inode fanotify_fid_inode(struct inode to_tell, u32 event_mask,
	const void *data, int data_type)
	{
	if (event_mask & ALL_FSNOTIFY_DIRENT_EVENTS)
	return to_tell;
	else if (data_type == FSNOTIFY_EVENT_INODE)
	return (struct inode *)data;
	else if (data_type == FSNOTIFY_EVENT_PATH)
	return d_inode(((struct path *)data)->dentry);
	return NULL;
	}

	struct fanotify_event fanotify_alloc_event(struct fsnotify_group group,
	struct inode *inode, u32 mask,
	const void *data, int data_type,
	__kernel_fsid_t *fsid)
	{
	struct fanotify_event *event = NULL;
	gfp_t gfp = GFP_KERNEL_ACCOUNT;
	struct inode *id = fanotify_fid_inode(inode, mask, data, data_type);

	/*
	* For queues with unlimited length lost events are not expected and
	* can possibly have security implications. Avoid losing events when
	* memory is short.
	*/
	if (group->max_events == UINT_MAX)
	gfp \|= __GFP_NOFAIL;

	/* Whoever is interested in the event, pays for the allocation. */
	memalloc_use_memcg(group->memcg);

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

	pevent = kmem_cache_alloc(fanotify_perm_event_cachep, gfp);
	if (!pevent)
	goto out;
	event = &pevent->fae;
	pevent->response = 0;
	pevent->state = FAN_EVENT_INIT;
	goto init;
	}
	event = kmem_cache_alloc(fanotify_event_cachep, gfp);
	if (!event)
	goto out;
	init: __maybe_unused
	fsnotify_init_event(&event->fse, inode);
	event->mask = mask;
	if (FAN_GROUP_FLAG(group, FAN_REPORT_TID))
	event->pid = get_pid(task_pid(current));
	else
	event->pid = get_pid(task_tgid(current));
	event->fh_len = 0;
	if (id && FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
	/* Report the event without a file identifier on encode error */
	event->fh_type = fanotify_encode_fid(event, id, gfp, fsid);
	} else if (data_type == FSNOTIFY_EVENT_PATH) {
	event->fh_type = FILEID_ROOT;
	event->path = ((struct path )data);
	path_get(&event->path);
	} else {
	event->fh_type = FILEID_INVALID;
	event->path.mnt = NULL;
	event->path.dentry = NULL;
	}
	out:
	memalloc_unuse_memcg();
	return event;
	}

	/*
	* Get cached fsid of the filesystem containing the object from any connector.
	* All connectors are supposed to have the same fsid, but we do not verify that
	* here.
	*/
	static __kernel_fsid_t fanotify_get_fsid(struct fsnotify_iter_info *iter_info)
	{
	int type;
	__kernel_fsid_t fsid = {};

	fsnotify_foreach_obj_type(type) {
	struct fsnotify_mark_connector *conn;

	if (!fsnotify_iter_should_report_type(iter_info, type))
	continue;

	conn = READ_ONCE(iter_info->marks[type]->connector);
	/* Mark is just getting destroyed or created? */
	if (!conn)
	continue;
	fsid = conn->fsid;
	if (WARN_ON_ONCE(!fsid.val[0] && !fsid.val[1]))
	continue;
	return fsid;
	}

	return fsid;
	}

	static int fanotify_handle_event(struct fsnotify_group *group,
	struct inode *inode,
	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 *event;
	struct fsnotify_event *fsn_event;
	__kernel_fsid_t fsid = {};

	BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
	BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
	BUILD_BUG_ON(FAN_ATTRIB != FS_ATTRIB);
	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_MOVED_TO != FS_MOVED_TO);
	BUILD_BUG_ON(FAN_MOVED_FROM != FS_MOVED_FROM);
	BUILD_BUG_ON(FAN_CREATE != FS_CREATE);
	BUILD_BUG_ON(FAN_DELETE != FS_DELETE);
	BUILD_BUG_ON(FAN_DELETE_SELF != FS_DELETE_SELF);
	BUILD_BUG_ON(FAN_MOVE_SELF != FS_MOVE_SELF);
	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);
	BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
	BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);

	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 19);

	mask = fanotify_group_event_mask(group, iter_info, mask, data,
	data_type);
	if (!mask)
	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;
	}

	if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
	fsid = fanotify_get_fsid(iter_info);
	/* Racing with mark destruction or creation? */
	if (!fsid.val[0] && !fsid.val[1])
	return 0;
	}

	event = fanotify_alloc_event(group, inode, mask, data, data_type,
	&fsid);
	ret = -ENOMEM;
	if (unlikely(!event)) {
	/*
	* We don't queue overflow events for permission events as
	* there the access is denied and so no event is in fact lost.
	*/
	if (!fanotify_is_perm_event(mask))
	fsnotify_queue_overflow(group);
	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 & FANOTIFY_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);
	}
	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 *event;

	event = FANOTIFY_E(fsn_event);
	if (fanotify_event_has_path(event))
	path_put(&event->path);
	else if (fanotify_event_has_ext_fh(event))
	kfree(event->fid.ext_fh);
	put_pid(event->pid);
	if (fanotify_is_perm_event(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,
	};