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authorAbhijith Das <adas@redhat.com>2012-12-19 10:48:01 -0500
committerSteven Whitehouse <swhiteho@redhat.com>2013-01-02 10:04:53 +0000
commitf1213cacc7ffc7d4cdef3692f22b28a2df3216f5 (patch)
tree323a502b74dc45a726b05c5b0bddccb77ba516df
parentec1487528bed94c4aaff3687834fe94203880fd6 (diff)
GFS2: Fix race in gfs2_rs_alloc
QE aio tests uncovered a race condition in gfs2_rs_alloc where it's possible to come out of the function with a valid ip->i_res allocation but it gets freed before use resulting in a NULL ptr dereference. This patch envelopes the initial short-circuit check for non-NULL ip->i_res into the mutex lock. With this patch, I was able to successfully run the reproducer test multiple times. Resolves: rhbz#878476 Signed-off-by: Abhi Das <adas@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
-rw-r--r--fs/gfs2/rgrp.c22
1 files changed, 10 insertions, 12 deletions
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 37ee061d899e..738b3888adc6 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -557,22 +557,20 @@ void gfs2_free_clones(struct gfs2_rgrpd *rgd)
*/
int gfs2_rs_alloc(struct gfs2_inode *ip)
{
- struct gfs2_blkreserv *res;
+ int error = 0;
+ down_write(&ip->i_rw_mutex);
if (ip->i_res)
- return 0;
-
- res = kmem_cache_zalloc(gfs2_rsrv_cachep, GFP_NOFS);
- if (!res)
- return -ENOMEM;
+ goto out;
- RB_CLEAR_NODE(&res->rs_node);
+ ip->i_res = kmem_cache_zalloc(gfs2_rsrv_cachep, GFP_NOFS);
+ if (!ip->i_res) {
+ error = -ENOMEM;
+ goto out;
+ }
- down_write(&ip->i_rw_mutex);
- if (ip->i_res)
- kmem_cache_free(gfs2_rsrv_cachep, res);
- else
- ip->i_res = res;
+ RB_CLEAR_NODE(&ip->i_res->rs_node);
+out:
up_write(&ip->i_rw_mutex);
return 0;
}