fsnotify: don't BUG in fsnotify_destroy_mark()

fed47485 · Miklos Szeredi <[email protected]> · 2012-01-12 17:59:46 +01:00

Removing the parent of a watched file results in "kernel BUG at
fs/notify/mark.c:139".

To reproduce

  add "-w /tmp/audit/dir/watched_file" to audit.rules
  rm -rf /tmp/audit/dir

This is caused by fsnotify_destroy_mark() being called without an
extra reference taken by the caller.

Reported by Francesco Cosoleto here:

  https://bugzilla.novell.com/show_bug.cgi?id=689860

Fix by removing the BUG_ON and adding a comment about not accessing mark after
the iput.

Signed-off-by: Miklos Szeredi <[email protected]>
CC: [email protected]
Signed-off-by: Linus Torvalds <[email protected]>

Commit: fed474857efbed79cd390d0aee224231ca718f63
Parents: 1e6c4dfd

Changes

1 files changed · +5 −3

File	Status	Add	Del	Content
fs/notify/mark.c	modified	+5	−3	View file

fs/notify/mark.c

View file

diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index e14587d..f104d56 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -135,9 +135,6 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
 
 	mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
 
-	/* 1 from caller and 1 for being on i_list/g_list */
-	BUG_ON(atomic_read(&mark->refcnt) < 2);
-
 	spin_lock(&group->mark_lock);
 
 	if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
@@ -182,6 +179,11 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
 		iput(inode);
 
 	/*
+	 * We don't necessarily have a ref on mark from caller so the above iput
+	 * may have already destroyed it.  Don't touch from now on.
+	 */
+
+	/*
 	 * it's possible that this group tried to destroy itself, but this
 	 * this mark was simultaneously being freed by inode.  If that's the
 	 * case, we finish freeing the group here.