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authorBob Peterson <rpeterso@redhat.com>2013-12-10 12:06:35 -0500
committerSteven Whitehouse <swhiteho@redhat.com>2013-12-13 21:42:23 +0000
commit9290a9a7c0bcf5400e8dbfbf9707fa68ea3fb338 (patch)
tree93b5b33720730b873652bec3ee4b761cfe844845 /fs/gfs2
parentdfe5b9ad83a63180f358b27d1018649a27b394a9 (diff)
GFS2: Fix use-after-free race when calling gfs2_remove_from_ail
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>
Diffstat (limited to 'fs/gfs2')
-rw-r--r--fs/gfs2/log.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 610613fb65b5..9dcb9777a5f8 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -551,10 +551,10 @@ void gfs2_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd)
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);