gfs2: fix use-after-free in trans_drain

This patch adds code to function trans_drain to remove drained
bd elements from the ail lists, if queued, before freeing the bd.
If we don't remove the bd from the ail, function ail_drain will
try to reference the bd after it has been freed by trans_drain.

Thanks to Andy Price for his analysis of the problem.

Reported-by: Andy Price <anprice@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 16937ebb2a3e3463cdf176f90c877982abf93f5e..760af666576ccb26f82ad184d69addc028f41844 100644 (file)
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -998,12 +998,16 @@ static void trans_drain(struct gfs2_trans *tr)
        while (!list_empty(head)) {
                bd = list_first_entry(head, struct gfs2_bufdata, bd_list);
                list_del_init(&bd->bd_list);
+               if (!list_empty(&bd->bd_ail_st_list))
+                       gfs2_remove_from_ail(bd);
                kmem_cache_free(gfs2_bufdata_cachep, bd);
        }
        head = &tr->tr_databuf;
        while (!list_empty(head)) {
                bd = list_first_entry(head, struct gfs2_bufdata, bd_list);
                list_del_init(&bd->bd_list);
+               if (!list_empty(&bd->bd_ail_st_list))
+                       gfs2_remove_from_ail(bd);
                kmem_cache_free(gfs2_bufdata_cachep, bd);
        }
 }

diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index ab96cf0bf26bea1c9b10136e54a207baafaaa0d3..63fec11ef2ce3fe8c37ff0f76a923444ee0df7d6 100644 (file)
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -169,6 +169,8 @@ static struct gfs2_bufdata *gfs2_alloc_bufdata(struct gfs2_glock *gl,
        bd->bd_bh = bh;
        bd->bd_gl = gl;
        INIT_LIST_HEAD(&bd->bd_list);
+       INIT_LIST_HEAD(&bd->bd_ail_st_list);
+       INIT_LIST_HEAD(&bd->bd_ail_gl_list);
        bh->b_private = bd;
        return bd;
 }