linux-kernel - [PATCH 2/4] GFS2: Fix race in gfs2_rs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu,  3 Jan 2013 11:50:08 +0000
From:	Steven Whitehouse <swhiteho@...hat.com>
To:	cluster-devel@...hat.com, linux-kernel@...r.kernel.org
Cc:	Abhijith Das <adas@...hat.com>,
	Steven Whitehouse <swhiteho@...hat.com>
Subject: [PATCH 2/4] GFS2: Fix race in gfs2_rs_alloc

From: Abhijith Das <adas@...hat.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@...hat.com>
Signed-off-by: Steven Whitehouse <swhiteho@...hat.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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/