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authorLinus Torvalds <torvalds@linux-foundation.org>2015-07-21 16:06:53 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-07-21 16:06:53 -0700
commitd725e66c06ab440032f49ef17e960896d0ec6d49 (patch)
tree7d071492f1ab656913be0c892497d3204928ce0a /fs
parentMerge tag 'pinctrl-v4.2-2' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl (diff)
downloadlinux-dev-d725e66c06ab440032f49ef17e960896d0ec6d49.tar.xz
linux-dev-d725e66c06ab440032f49ef17e960896d0ec6d49.zip
Revert "fsnotify: fix oops in fsnotify_clear_marks_by_group_flags()"
This reverts commit a2673b6e040663bf16a552f8619e6bde9f4b9acf. Kinglong Mee reports a memory leak with that patch, and Jan Kara confirms: "Thanks for report! You are right that my patch introduces a race between fsnotify kthread and fsnotify_destroy_group() which can result in leaking inotify event on group destruction. I haven't yet decided whether the right fix is not to queue events for dying notification group (as that is pointless anyway) or whether we should just fix the original problem differently... Whenever I look at fsnotify code mark handling I get lost in the maze of locks, lists, and subtle differences between how different notification systems handle notification marks :( I'll think about it over night" and after thinking about it, Jan says: "OK, I have looked into the code some more and I found another relatively simple way of fixing the original oops. It will be IMHO better than trying to fixup this issue which has more potential for breakage. I'll ask Linus to revert the fsnotify fix he already merged and send a new fix" Reported-by: Kinglong Mee <kinglongmee@gmail.com> Requested-by: Jan Kara <jack@suse.cz> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/notify/mark.c34
1 files changed, 20 insertions, 14 deletions
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 3e594ce41010..92e48c70f0f0 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -152,15 +152,31 @@ void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
BUG();
list_del_init(&mark->g_list);
+
spin_unlock(&mark->lock);
if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED))
iput(inode);
+ /* release lock temporarily */
+ mutex_unlock(&group->mark_mutex);
spin_lock(&destroy_lock);
list_add(&mark->g_list, &destroy_list);
spin_unlock(&destroy_lock);
wake_up(&destroy_waitq);
+ /*
+ * We don't necessarily have a ref on mark from caller so the above destroy
+ * may have actually freed it, unless this group provides a 'freeing_mark'
+ * function which must be holding a reference.
+ */
+
+ /*
+ * Some groups like to know that marks are being freed. This is a
+ * callback to the group function to let it know that this mark
+ * is being freed.
+ */
+ if (group->ops->freeing_mark)
+ group->ops->freeing_mark(mark, group);
/*
* __fsnotify_update_child_dentry_flags(inode);
@@ -175,6 +191,8 @@ void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
*/
atomic_dec(&group->num_marks);
+
+ mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
}
void fsnotify_destroy_mark(struct fsnotify_mark *mark,
@@ -187,10 +205,7 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark,
/*
* Destroy all marks in the given list. The marks must be already detached from
- * the original inode / vfsmount. Note that we can race with
- * fsnotify_clear_marks_by_group_flags(). However we hold a reference to each
- * mark so they won't get freed from under us and nobody else touches our
- * free_list list_head.
+ * the original inode / vfsmount.
*/
void fsnotify_destroy_marks(struct list_head *to_free)
{
@@ -391,7 +406,7 @@ struct fsnotify_mark *fsnotify_find_mark(struct hlist_head *head,
}
/*
- * Clear any marks in a group in which mark->flags & flags is true.
+ * clear any marks in a group in which mark->flags & flags is true
*/
void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group,
unsigned int flags)
@@ -445,7 +460,6 @@ static int fsnotify_mark_destroy(void *ignored)
{
struct fsnotify_mark *mark, *next;
struct list_head private_destroy_list;
- struct fsnotify_group *group;
for (;;) {
spin_lock(&destroy_lock);
@@ -457,14 +471,6 @@ static int fsnotify_mark_destroy(void *ignored)
list_for_each_entry_safe(mark, next, &private_destroy_list, g_list) {
list_del_init(&mark->g_list);
- group = mark->group;
- /*
- * Some groups like to know that marks are being freed.
- * This is a callback to the group function to let it
- * know that this mark is being freed.
- */
- if (group && group->ops->freeing_mark)
- group->ops->freeing_mark(mark, group);
fsnotify_put_mark(mark);
}