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fsnotify: don't BUG in fsnotify_destroy_mark()

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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 <mszeredi@suse.cz>
CC: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Miklos Szeredi 2012-01-12 17:59:46 +01:00 committed by Linus Torvalds
parent 1e6c4dfdeb
commit fed474857e
1 changed files with 5 additions and 3 deletions
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8
fs/notify/mark.c
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@ -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) {
@ -181,6 +178,11 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED))
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