[PATCH 0/6] Fanotify cleanups

[PATCH 0/6] Fanotify cleanups

[Jan Kara]

  Hello,

  when fixing use-after-free bug with fanotify introduced by my previous
cleanup patches (the fix is already merged by Linus), I have better understood
handling of permission events and found a couple of things that can be further
cleaned up.  This patch series removes some dead code (patches 1/6 and 3/6),
uses the notify structure itself for processing response to permission event
(patch 2/6) thus saving some space and allocation, converts access_mutex to
spinlock (patch 4/6) which should be faster, and moves code around
copy_event_to_user() to make code more readable (patch 5/6, 6/6).

The patches pass LTP fanotify tests. Andrew, can you please take the patches
for the next merge window?

								Honza

[PATCH 1/6] fanotify: Remove useless bypass_perm check

[Jan Kara]

prepare_for_access_response() checks whether
group->fanotify_data.bypass_perm is set. However this test can never be
true because prepare_for_access_response() is called only from
fanotify_read() which means fanotify group is alive with an active fd
while bypass_perm is set from fanotify_release() when all file
descriptors pointing to the group are closed and the group is going
away.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/notify/fanotify/fanotify_user.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index b6175fa11bf8..4ad8b711bfde 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -211,14 +211,6 @@ static int prepare_for_access_response(struct fsnotify_group *group,
 	re->fd = fd;
 
 	mutex_lock(&group->fanotify_data.access_mutex);
-
-	if (atomic_read(&group->fanotify_data.bypass_perm)) {
-		mutex_unlock(&group->fanotify_data.access_mutex);
-		kmem_cache_free(fanotify_response_event_cache, re);
-		FANOTIFY_E(event)->response = FAN_ALLOW;
-		return 0;
-	}
-		
 	list_add_tail(&re->list, &group->fanotify_data.access_list);
 	mutex_unlock(&group->fanotify_data.access_mutex);
 
-- 
1.8.1.4

[PATCH 2/6] fanotify: Use fanotify event structure for permission response processing

[Jan Kara]

Currently, fanotify creates new structure to track the fact that
permission event has been reported to userspace and someone is waiting
for a response to it. As event structures are now completely in the
hands of each notification framework, we can use the event structure
for this tracking instead of allocating a new structure.

Since this makes the event structures for normal events and permission
events even more different and the structures have different lifetime
rules, we split them into two separate structures (where permission
event structure contains the structure for a normal event). This makes
normal events 8 bytes smaller and the code a tad bit cleaner.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/notify/fanotify/fanotify.c      |  63 +++++++++++++++------
 fs/notify/fanotify/fanotify.h      |  31 +++++++---
 fs/notify/fanotify/fanotify_user.c | 113 +++++++++++++------------------------
 3 files changed, 109 insertions(+), 98 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 0e792f5e3147..6c5369f0f78c 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -60,8 +60,8 @@ static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
 }
 
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-static int fanotify_get_response_from_access(struct fsnotify_group *group,
-					     struct fanotify_event_info *event)
+static int fanotify_get_response(struct fsnotify_group *group,
+				 struct fanotify_perm_event_info *event)
 {
 	int ret;
 
@@ -142,6 +142,40 @@ static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark,
 	return false;
 }
 
+static struct fanotify_event_info *alloc_event(struct inode *inode, u32 mask,
+					       struct path *path)
+{
+	struct fanotify_event_info *event;
+
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+	if (mask & FAN_ALL_PERM_EVENTS) {
+		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;
+	}
+#endif
+	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 (data_type == FSNOTIFY_EVENT_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,
@@ -171,25 +205,11 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 	pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
 		 mask);
 
-	event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
+	event = alloc_event(inode, mask, data);
 	if (unlikely(!event))
 		return -ENOMEM;
 
 	fsn_event = &event->fse;
-	fsnotify_init_event(fsn_event, inode, mask);
-	event->tgid = get_pid(task_tgid(current));
-	if (data_type == FSNOTIFY_EVENT_PATH) {
-		struct path *path = data;
-		event->path = *path;
-		path_get(&event->path);
-	} else {
-		event->path.mnt = NULL;
-		event->path.dentry = NULL;
-	}
-#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-	event->response = 0;
-#endif
-
 	ret = fsnotify_add_notify_event(group, fsn_event, fanotify_merge);
 	if (ret) {
 		BUG_ON(mask & FAN_ALL_PERM_EVENTS);
@@ -200,7 +220,7 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 	if (mask & FAN_ALL_PERM_EVENTS) {
-		ret = fanotify_get_response_from_access(group, event);
+		ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event));
 		fsnotify_destroy_event(group, fsn_event);
 	}
 #endif
@@ -223,6 +243,13 @@ static void fanotify_free_event(struct fsnotify_event *fsn_event)
 	event = FANOTIFY_E(fsn_event);
 	path_put(&event->path);
 	put_pid(event->tgid);
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+	if (fsn_event->mask & FAN_ALL_PERM_EVENTS) {
+		kmem_cache_free(fanotify_perm_event_cachep,
+				FANOTIFY_PE(fsn_event));
+		return;
+	}
+#endif
 	kmem_cache_free(fanotify_event_cachep, event);
 }
 
diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index 32a2f034fb94..ffacf43b8072 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -3,13 +3,12 @@
 #include <linux/slab.h>
 
 extern struct kmem_cache *fanotify_event_cachep;
+extern struct kmem_cache *fanotify_perm_event_cachep;
 
 /*
- * Lifetime of the structure differs for normal and permission events. In both
- * cases the structure is allocated in fanotify_handle_event(). For normal
- * events the structure is freed immediately after reporting it to userspace.
- * For permission events we free it only after we receive response from
- * userspace.
+ * Structure for normal fanotify events. It gets allocated in
+ * fanotify_handle_event() and freed when the information is retrieved by
+ * userspace
  */
 struct fanotify_event_info {
 	struct fsnotify_event fse;
@@ -19,11 +18,29 @@ struct fanotify_event_info {
 	 */
 	struct path path;
 	struct pid *tgid;
+};
+
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-	u32 response;	/* userspace answer to question */
-#endif
+/*
+ * Structure for permission fanotify events. It gets allocated and freed in
+ * fanotify_handle_event() since we wait there for user response. When the
+ * information is retrieved by userspace the structure is moved from
+ * group->notification_list to group->fanotify_data.access_list to wait for
+ * user response.
+ */
+struct fanotify_perm_event_info {
+	struct fanotify_event_info fae;
+	int response;	/* userspace answer to question */
+	int fd;		/* fd we passed to userspace for this event */
 };
 
+static inline struct fanotify_perm_event_info *
+FANOTIFY_PE(struct fsnotify_event *fse)
+{
+	return container_of(fse, struct fanotify_perm_event_info, fae.fse);
+}
+#endif
+
 static inline struct fanotify_event_info *FANOTIFY_E(struct fsnotify_event *fse)
 {
 	return container_of(fse, struct fanotify_event_info, fse);
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 4ad8b711bfde..e22640e71e83 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -28,14 +28,8 @@
 extern const struct fsnotify_ops fanotify_fsnotify_ops;
 
 static struct kmem_cache *fanotify_mark_cache __read_mostly;
-static struct kmem_cache *fanotify_response_event_cache __read_mostly;
 struct kmem_cache *fanotify_event_cachep __read_mostly;
-
-struct fanotify_response_event {
-	struct list_head list;
-	__s32 fd;
-	struct fanotify_event_info *event;
-};
+struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
 
 /*
  * Get an fsnotify notification event if one exists and is small
@@ -135,33 +129,34 @@ static int fill_event_metadata(struct fsnotify_group *group,
 }
 
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-static struct fanotify_response_event *dequeue_re(struct fsnotify_group *group,
-						  __s32 fd)
+static struct fanotify_perm_event_info *dequeue_event(
+				struct fsnotify_group *group, int fd)
 {
-	struct fanotify_response_event *re, *return_re = NULL;
+	struct fanotify_perm_event_info *event, *return_e = NULL;
 
 	mutex_lock(&group->fanotify_data.access_mutex);
-	list_for_each_entry(re, &group->fanotify_data.access_list, list) {
-		if (re->fd != fd)
+	list_for_each_entry(event, &group->fanotify_data.access_list,
+			    fae.fse.list) {
+		if (event->fd != fd)
 			continue;
 
-		list_del_init(&re->list);
-		return_re = re;
+		list_del_init(&event->fae.fse.list);
+		return_e = event;
 		break;
 	}
 	mutex_unlock(&group->fanotify_data.access_mutex);
 
-	pr_debug("%s: found return_re=%p\n", __func__, return_re);
+	pr_debug("%s: found return_re=%p\n", __func__, return_e);
 
-	return return_re;
+	return return_e;
 }
 
 static int process_access_response(struct fsnotify_group *group,
 				   struct fanotify_response *response_struct)
 {
-	struct fanotify_response_event *re;
-	__s32 fd = response_struct->fd;
-	__u32 response = response_struct->response;
+	struct fanotify_perm_event_info *event;
+	int fd = response_struct->fd;
+	int response = response_struct->response;
 
 	pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
 		 fd, response);
@@ -181,50 +176,15 @@ static int process_access_response(struct fsnotify_group *group,
 	if (fd < 0)
 		return -EINVAL;
 
-	re = dequeue_re(group, fd);
-	if (!re)
+	event = dequeue_event(group, fd);
+	if (!event)
 		return -ENOENT;
 
-	re->event->response = response;
-
+	event->response = response;
 	wake_up(&group->fanotify_data.access_waitq);
 
-	kmem_cache_free(fanotify_response_event_cache, re);
-
-	return 0;
-}
-
-static int prepare_for_access_response(struct fsnotify_group *group,
-				       struct fsnotify_event *event,
-				       __s32 fd)
-{
-	struct fanotify_response_event *re;
-
-	if (!(event->mask & FAN_ALL_PERM_EVENTS))
-		return 0;
-
-	re = kmem_cache_alloc(fanotify_response_event_cache, GFP_KERNEL);
-	if (!re)
-		return -ENOMEM;
-
-	re->event = FANOTIFY_E(event);
-	re->fd = fd;
-
-	mutex_lock(&group->fanotify_data.access_mutex);
-	list_add_tail(&re->list, &group->fanotify_data.access_list);
-	mutex_unlock(&group->fanotify_data.access_mutex);
-
-	return 0;
-}
-
-#else
-static int prepare_for_access_response(struct fsnotify_group *group,
-				       struct fsnotify_event *event,
-				       __s32 fd)
-{
 	return 0;
 }
-
 #endif
 
 static ssize_t copy_event_to_user(struct fsnotify_group *group,
@@ -247,9 +207,15 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 			 fanotify_event_metadata.event_len))
 		goto out_close_fd;
 
-	ret = prepare_for_access_response(group, event, fd);
-	if (ret)
-		goto out_close_fd;
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+	if (event->mask & FAN_ALL_PERM_EVENTS) {
+		FANOTIFY_PE(event)->fd = fd;
+		mutex_lock(&group->fanotify_data.access_mutex);
+		list_add_tail(&event->fae.fse.list,
+			      &group->fanotify_data.access_list);
+		mutex_unlock(&group->fanotify_data.access_mutex);
+	}
+#endif
 
 	if (fd != FAN_NOFD)
 		fd_install(fd, f);
@@ -263,7 +229,7 @@ out_close_fd:
 out:
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 	if (event->mask & FAN_ALL_PERM_EVENTS) {
-		FANOTIFY_E(event)->response = FAN_DENY;
+		FANOTIFY_PE(event)->response = FAN_DENY;
 		wake_up(&group->fanotify_data.access_waitq);
 	}
 #endif
@@ -312,8 +278,8 @@ static ssize_t fanotify_read(struct file *file, char __user *buf,
 				break;
 			ret = copy_event_to_user(group, kevent, buf);
 			/*
-			 * Permission events get destroyed after we
-			 * receive response
+			 * Permission events get queued to wait for response.
+			 * Other events can be destroyed now.
 			 */
 			if (!(kevent->mask & FAN_ALL_PERM_EVENTS))
 				fsnotify_destroy_event(group, kevent);
@@ -375,20 +341,19 @@ static int fanotify_release(struct inode *ignored, struct file *file)
 	struct fsnotify_group *group = file->private_data;
 
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-	struct fanotify_response_event *re, *lre;
+	struct fanotify_perm_event_info *event, *next;
 
 	mutex_lock(&group->fanotify_data.access_mutex);
 
 	atomic_inc(&group->fanotify_data.bypass_perm);
 
-	list_for_each_entry_safe(re, lre, &group->fanotify_data.access_list, list) {
-		pr_debug("%s: found group=%p re=%p event=%p\n", __func__, group,
-			 re, re->event);
-
-		list_del_init(&re->list);
-		re->event->response = FAN_ALLOW;
+	list_for_each_entry_safe(event, next, &group->fanotify_data.access_list,
+				 fae.fse.list) {
+		pr_debug("%s: found group=%p event=%p\n", __func__, group,
+			 event);
 
-		kmem_cache_free(fanotify_response_event_cache, re);
+		list_del_init(&event->fae.fse.list);
+		event->response = FAN_ALLOW;
 	}
 	mutex_unlock(&group->fanotify_data.access_mutex);
 
@@ -899,9 +864,11 @@ COMPAT_SYSCALL_DEFINE6(fanotify_mark,
 static int __init fanotify_user_setup(void)
 {
 	fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
-	fanotify_response_event_cache = KMEM_CACHE(fanotify_response_event,
-						   SLAB_PANIC);
 	fanotify_event_cachep = KMEM_CACHE(fanotify_event_info, SLAB_PANIC);
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+	fanotify_perm_event_cachep = KMEM_CACHE(fanotify_perm_event_info,
+						SLAB_PANIC);
+#endif
 
 	return 0;
 }
-- 
1.8.1.4

[PATCH 3/6] fanotify: Remove useless test from event initialization

[Jan Kara]

Fanotify processes only path events (fanotify_should_send_event()
refuses any other event) so checking whether event is a path event
during initialization makes no sense.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/notify/fanotify/fanotify.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 6c5369f0f78c..3c40f9685453 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -166,13 +166,8 @@ static struct fanotify_event_info *alloc_event(struct inode *inode, u32 mask,
 init: __maybe_unused
 	fsnotify_init_event(&event->fse, inode, mask);
 	event->tgid = get_pid(task_tgid(current));
-	if (data_type == FSNOTIFY_EVENT_PATH) {
-		event->path = *path;
-		path_get(&event->path);
-	} else {
-		event->path.mnt = NULL;
-		event->path.dentry = NULL;
-	}
+	event->path = *path;
+	path_get(&event->path);
 	return event;
 }
 
-- 
1.8.1.4

[PATCH 4/6] fanotify: Convert access_mutex to spinlock

[Jan Kara]

access_mutex is used only to guard operations on access_list. There's no
need for sleeping within this lock so just make a spinlock out of it.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/notify/fanotify/fanotify_user.c | 14 +++++++-------
 include/linux/fsnotify_backend.h   |  2 +-
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index e22640e71e83..5947fecb69c4 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -134,7 +134,7 @@ static struct fanotify_perm_event_info *dequeue_event(
 {
 	struct fanotify_perm_event_info *event, *return_e = NULL;
 
-	mutex_lock(&group->fanotify_data.access_mutex);
+	spin_lock(&group->fanotify_data.access_lock);
 	list_for_each_entry(event, &group->fanotify_data.access_list,
 			    fae.fse.list) {
 		if (event->fd != fd)
@@ -144,7 +144,7 @@ static struct fanotify_perm_event_info *dequeue_event(
 		return_e = event;
 		break;
 	}
-	mutex_unlock(&group->fanotify_data.access_mutex);
+	spin_unlock(&group->fanotify_data.access_lock);
 
 	pr_debug("%s: found return_re=%p\n", __func__, return_e);
 
@@ -210,10 +210,10 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 	if (event->mask & FAN_ALL_PERM_EVENTS) {
 		FANOTIFY_PE(event)->fd = fd;
-		mutex_lock(&group->fanotify_data.access_mutex);
+		spin_lock(&group->fanotify_data.access_lock);
 		list_add_tail(&event->fae.fse.list,
 			      &group->fanotify_data.access_list);
-		mutex_unlock(&group->fanotify_data.access_mutex);
+		spin_unlock(&group->fanotify_data.access_lock);
 	}
 #endif
 
@@ -343,7 +343,7 @@ static int fanotify_release(struct inode *ignored, struct file *file)
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 	struct fanotify_perm_event_info *event, *next;
 
-	mutex_lock(&group->fanotify_data.access_mutex);
+	spin_lock(&group->fanotify_data.access_lock);
 
 	atomic_inc(&group->fanotify_data.bypass_perm);
 
@@ -355,7 +355,7 @@ static int fanotify_release(struct inode *ignored, struct file *file)
 		list_del_init(&event->fae.fse.list);
 		event->response = FAN_ALLOW;
 	}
-	mutex_unlock(&group->fanotify_data.access_mutex);
+	spin_unlock(&group->fanotify_data.access_lock);
 
 	wake_up(&group->fanotify_data.access_waitq);
 #endif
@@ -689,7 +689,7 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 
 	group->fanotify_data.f_flags = event_f_flags;
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-	mutex_init(&group->fanotify_data.access_mutex);
+	spin_lock_init(&group->fanotify_data.access_lock);
 	init_waitqueue_head(&group->fanotify_data.access_waitq);
 	INIT_LIST_HEAD(&group->fanotify_data.access_list);
 	atomic_set(&group->fanotify_data.bypass_perm, 0);
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 3d286ff49ab0..e4f238f708bb 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -178,7 +178,7 @@ struct fsnotify_group {
 		struct fanotify_group_private_data {
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 			/* allows a group to block waiting for a userspace response */
-			struct mutex access_mutex;
+			spinlock_t access_lock;
 			struct list_head access_list;
 			wait_queue_head_t access_waitq;
 			atomic_t bypass_perm;
-- 
1.8.1.4

[PATCH 5/6] fanotify: Reorganize loop in fanotify_read()

[Jan Kara]

Swap the error / "read ok" branches in the main loop of fanotify_read().
We will grow the "read ok" part in the next patch and this makes the
indentation easier. Also it is more common to have error conditions
inside an 'if' instead of the fast path.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/notify/fanotify/fanotify_user.c | 46 ++++++++++++++++++++------------------
 1 file changed, 24 insertions(+), 22 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 5947fecb69c4..18e95400b715 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -272,35 +272,37 @@ static ssize_t fanotify_read(struct file *file, char __user *buf,
 		kevent = get_one_event(group, count);
 		mutex_unlock(&group->notification_mutex);
 
-		if (kevent) {
+		if (IS_ERR(kevent)) {
 			ret = PTR_ERR(kevent);
-			if (IS_ERR(kevent))
+			break;
+		}
+
+		if (!kevent) {
+			ret = -EAGAIN;
+			if (file->f_flags & O_NONBLOCK)
 				break;
-			ret = copy_event_to_user(group, kevent, buf);
-			/*
-			 * Permission events get queued to wait for response.
-			 * Other events can be destroyed now.
-			 */
-			if (!(kevent->mask & FAN_ALL_PERM_EVENTS))
-				fsnotify_destroy_event(group, kevent);
-			if (ret < 0)
+
+			ret = -ERESTARTSYS;
+			if (signal_pending(current))
+				break;
+
+			if (start != buf)
 				break;
-			buf += ret;
-			count -= ret;
+			schedule();
 			continue;
 		}
 
-		ret = -EAGAIN;
-		if (file->f_flags & O_NONBLOCK)
-			break;
-		ret = -ERESTARTSYS;
-		if (signal_pending(current))
-			break;
-
-		if (start != buf)
+		ret = copy_event_to_user(group, kevent, buf);
+		/*
+		 * Permission events get queued to wait for response.  Other
+		 * events can be destroyed now.
+		 */
+		if (!(kevent->mask & FAN_ALL_PERM_EVENTS))
+			fsnotify_destroy_event(group, kevent);
+		if (ret < 0)
 			break;
-
-		schedule();
+		buf += ret;
+		count -= ret;
 	}
 
 	finish_wait(&group->notification_waitq, &wait);
-- 
1.8.1.4

[PATCH 6/6] fanotify: Move unrelated handling from copy_event_to_user()

[Jan Kara]

Move code moving event structure to access_list from
copy_event_to_user() to fanotify_read() where it is more logical (so
that we can immediately see in the main loop that we either move the
event to a different list or free it). Also move special error handling
for permission events from copy_event_to_user() to the main loop to have
it in one place with error handling for normal events.  This makes
copy_event_to_user() really only copy the event to user without any side
effects.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/notify/fanotify/fanotify_user.c | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 18e95400b715..c3406d633925 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -199,7 +199,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 
 	ret = fill_event_metadata(group, &fanotify_event_metadata, event, &f);
 	if (ret < 0)
-		goto out;
+		return ret;
 
 	fd = fanotify_event_metadata.fd;
 	ret = -EFAULT;
@@ -208,13 +208,8 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 		goto out_close_fd;
 
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-	if (event->mask & FAN_ALL_PERM_EVENTS) {
+	if (event->mask & FAN_ALL_PERM_EVENTS)
 		FANOTIFY_PE(event)->fd = fd;
-		spin_lock(&group->fanotify_data.access_lock);
-		list_add_tail(&event->fae.fse.list,
-			      &group->fanotify_data.access_list);
-		spin_unlock(&group->fanotify_data.access_lock);
-	}
 #endif
 
 	if (fd != FAN_NOFD)
@@ -226,13 +221,6 @@ out_close_fd:
 		put_unused_fd(fd);
 		fput(f);
 	}
-out:
-#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-	if (event->mask & FAN_ALL_PERM_EVENTS) {
-		FANOTIFY_PE(event)->response = FAN_DENY;
-		wake_up(&group->fanotify_data.access_waitq);
-	}
-#endif
 	return ret;
 }
 
@@ -297,10 +285,23 @@ static ssize_t fanotify_read(struct file *file, char __user *buf,
 		 * Permission events get queued to wait for response.  Other
 		 * events can be destroyed now.
 		 */
-		if (!(kevent->mask & FAN_ALL_PERM_EVENTS))
+		if (!(kevent->mask & FAN_ALL_PERM_EVENTS)) {
 			fsnotify_destroy_event(group, kevent);
-		if (ret < 0)
-			break;
+			if (ret < 0)
+				break;
+		} else {
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+			if (ret < 0) {
+				FANOTIFY_PE(kevent)->response = FAN_DENY;
+				wake_up(&group->fanotify_data.access_waitq);
+				break;
+			}
+			spin_lock(&group->fanotify_data.access_lock);
+			list_add_tail(&kevent->list,
+				      &group->fanotify_data.access_list);
+			spin_unlock(&group->fanotify_data.access_lock);
+#endif
+		}
 		buf += ret;
 		count -= ret;
 	}
-- 
1.8.1.4