lkml.org 
[lkml]   [2013]   [Jan]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 2/4] GFS2: Fix race in gfs2_rs_alloc
Date
From: Abhijith Das <adas@redhat.com>

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>

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 37ee061..738b388 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;
}
--
1.7.4


\
 
 \ /
  Last update: 2013-01-03 14:01    [W:0.777 / U:0.436 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site