linux-kernel - Re: [PATCH resend] audit: fix mark refcounting

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Date:	Thu, 15 Dec 2011 10:03:41 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Eric Paris <eparis@...hat.com>, akpm@...ux-foundation.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH resend] audit: fix mark refcounting

Updated patch:

----
From: Miklos Szeredi <mszeredi@...e.cz>
Subject: fsnotify: hold reference to mark around destroy

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

Linus noticed that the call in

 fs/notify/inotify/inotify_fsnotify.c

has also missing reference to mark.

Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
CC: Al Viro <viro@...iv.linux.org.uk>
CC: Eric Paris <eparis@...hat.com>
CC: stable@...r.kernel.org
---
 fs/notify/inotify/inotify_fsnotify.c |    5 ++++-
 kernel/audit_watch.c                 |    2 ++
 2 files changed, 6 insertions(+), 1 deletion(-)

Index: linux.git/kernel/audit_watch.c
===================================================================
--- linux.git.orig/kernel/audit_watch.c	2011-12-14 13:59:47.000000000 +0100
+++ linux.git/kernel/audit_watch.c	2011-12-15 09:57:53.000000000 +0100
@@ -349,7 +349,9 @@ static void audit_remove_parent_watches(
 	}
 	mutex_unlock(&audit_filter_mutex);
 
+	audit_get_parent(parent);
 	fsnotify_destroy_mark(&parent->mark);
+	audit_put_parent(parent);
 }
 
 /* Get path information necessary for adding watches. */
Index: linux.git/fs/notify/inotify/inotify_fsnotify.c
===================================================================
--- linux.git.orig/fs/notify/inotify/inotify_fsnotify.c	2011-09-13 16:08:20.000000000 +0200
+++ linux.git/fs/notify/inotify/inotify_fsnotify.c	2011-12-15 09:59:15.000000000 +0100
@@ -130,8 +130,11 @@ static int inotify_handle_event(struct f
 			ret = PTR_ERR(added_event);
 	}
 
-	if (inode_mark->mask & IN_ONESHOT)
+	if (inode_mark->mask & IN_ONESHOT) {
+		fsnotify_get_mark(inode_mark);
 		fsnotify_destroy_mark(inode_mark);
+		fsnotify_put_mark(inode_mark);
+	}
 
 	return ret;
 }
--
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