[ 3.8.y.z extended stable ] Patch "jbd2: Fix use after free after error in jbd2_journal_dirty_metadata()" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    jbd2: Fix use after free after error in jbd2_journal_dirty_metadata()

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.8.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From da911b91d330eaedba57dc874cc9cf5d83ef2b55 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack at suse.cz>
Date: Mon, 12 Aug 2013 09:53:28 -0400
Subject: jbd2: Fix use after free after error in jbd2_journal_dirty_metadata()

commit 91aa11fae1cf8c2fd67be0609692ea9741cdcc43 upstream.

When jbd2_journal_dirty_metadata() returns error,
__ext4_handle_dirty_metadata() stops the handle. However callers of this
function do not count with that fact and still happily used now freed
handle. This use after free can result in various issues but very likely
we oops soon.

The motivation of adding __ext4_journal_stop() into
__ext4_handle_dirty_metadata() in commit 9ea7a0df seems to be only to
improve error reporting. So replace __ext4_journal_stop() with
ext4_journal_abort_handle() which was there before that commit and add
WARN_ON_ONCE() to dump stack to provide useful information.

Reported-by: Sage Weil <sage at inktank.com>
Signed-off-by: Jan Kara <jack at suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso at mit.edu>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/ext4/ext4_jbd2.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
index b4323ba..6d7abb1 100644
--- a/fs/ext4/ext4_jbd2.c
+++ b/fs/ext4/ext4_jbd2.c
@@ -109,10 +109,10 @@ int __ext4_handle_dirty_metadata(const char *where, unsigned int line,

 	if (ext4_handle_valid(handle)) {
 		err = jbd2_journal_dirty_metadata(handle, bh);
-		if (err) {
-			/* Errors can only happen if there is a bug */
-			handle->h_err = err;
-			__ext4_journal_stop(where, line, handle);
+		/* Errors can only happen if there is a bug */
+		if (WARN_ON_ONCE(err)) {
+			ext4_journal_abort_handle(where, line, __func__, bh,
+						  handle, err);
 		}
 	} else {
 		if (inode)
--
1.8.1.2