| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.12 126/144] GFS2: Fix use-after-free race when calling gfs2_remove_from_ail | Date | Mon, 6 Jan 2014 14:38:07 -0800 |
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3.12-stable review patch. If anyone has any objections, please let me know.
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From: Bob Peterson <rpeterso@redhat.com>
commit 9290a9a7c0bcf5400e8dbfbf9707fa68ea3fb338 upstream.
Function gfs2_remove_from_ail drops the reference on the bh via brelse. This patch fixes a race condition whereby bh is deferenced after the brelse when setting bd->bd_blkno = bh->b_blocknr; Under certain rare circumstances, bh might be gone or reused, and bd->bd_blkno is set to whatever that memory happens to be, which is often 0. Later, in gfs2_trans_add_unrevoke, that bd fails the test "bd->bd_blkno >= blkno" which causes it to never be freed. The end result is that the bd is never freed from the bufdata cache, which results in this error: slab error in kmem_cache_destroy(): cache `gfs2_bufdata': Can't free all objects
Signed-off-by: Bob Peterson <rpeterso@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- fs/gfs2/log.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/fs/gfs2/log.c +++ b/fs/gfs2/log.c @@ -551,10 +551,10 @@ void gfs2_add_revoke(struct gfs2_sbd *sd struct buffer_head *bh = bd->bd_bh; struct gfs2_glock *gl = bd->bd_gl; - gfs2_remove_from_ail(bd); - bd->bd_bh = NULL; bh->b_private = NULL; bd->bd_blkno = bh->b_blocknr; + gfs2_remove_from_ail(bd); /* drops ref on bh */ + bd->bd_bh = NULL; bd->bd_ops = &gfs2_revoke_lops; sdp->sd_log_num_revoke++; atomic_inc(&gl->gl_revokes);
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