From: Jan Kara <jack@suse.cz>
Date: Mon, 16 Jun 2014 03:46:28 +0000 (-0400)
Subject: ext4: Fix buffer double free in ext4_alloc_branch()
X-Git-Tag: omap-for-v3.16/fixes-rc4~32^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c5c7b8ddfbf8cb3b2291e515a34ab1b8982f5a2d;p=pandora-kernel.git

ext4: Fix buffer double free in ext4_alloc_branch()

Error recovery in ext4_alloc_branch() calls ext4_forget() even for
buffer corresponding to indirect block it did not allocate. This leads
to brelse() being called twice for that buffer (once from ext4_forget()
and once from cleanup in ext4_ind_map_blocks()) leading to buffer use
count misaccounting. Eventually (but often much later because there
are other users of the buffer) we will see messages like:
VFS: brelse: Trying to free free buffer

Another manifestation of this problem is an error:
JBD2 unexpected failure: jbd2_journal_revoke: !buffer_revoked(bh);
inconsistent data on disk

The fix is easy - don't forget buffer we did not allocate. Also add an
explanatory comment because the indexing at ext4_alloc_branch() is
somewhat subtle.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
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