[Cluster-devel] [GFS2 PATCH] [bz878476] - Fix race in gfs2_rs_alloc
Steven Whitehouse
swhiteho at redhat.com
Wed Dec 19 16:23:10 UTC 2012
Hi,
I've added that to my tree of pending patches. That will be in the -nmw
tree just as soon as -rc1 is out. Thanks,
Steve.
On Wed, 2012-12-19 at 10:48 -0500, Abhijith Das wrote:
> 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 at 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;
> }
>
More information about the Cluster-devel
mailing list