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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>
This commit is contained in:
Bob Peterson 2021-02-25 11:11:09 -05:00 committed by Andreas Gruenbacher
parent eb602521f4
commit 1a5a2cfd34
2 changed files with 6 additions and 0 deletions
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4
fs/gfs2/log.c
View File

@ -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);
}
}

2
fs/gfs2/trans.c
View File

@ -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;
}