Commit f1213cac authored by Abhijith Das's avatar Abhijith Das Committed by Steven Whitehouse

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: default avatarAbhi Das <adas@redhat.com>
Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
parent ec148752
...@@ -557,22 +557,20 @@ void gfs2_free_clones(struct gfs2_rgrpd *rgd) ...@@ -557,22 +557,20 @@ void gfs2_free_clones(struct gfs2_rgrpd *rgd)
*/ */
int gfs2_rs_alloc(struct gfs2_inode *ip) 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) if (ip->i_res)
return 0; goto out;
res = kmem_cache_zalloc(gfs2_rsrv_cachep, GFP_NOFS);
if (!res)
return -ENOMEM;
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); RB_CLEAR_NODE(&ip->i_res->rs_node);
if (ip->i_res) out:
kmem_cache_free(gfs2_rsrv_cachep, res);
else
ip->i_res = res;
up_write(&ip->i_rw_mutex); up_write(&ip->i_rw_mutex);
return 0; return 0;
} }
......
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