From: Slava Pestov <sp@daterainc.com>
Date: Sun, 13 Jul 2014 04:53:11 +0000 (-0700)
Subject: bcache: fix use-after-free in btree_gc_coalesce()
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=400ffaa2acd72274e2c7293a9724382383bebf3e;p=deliverable%2Flinux.git

bcache: fix use-after-free in btree_gc_coalesce()

If we goto out_nocoalesce after we free new_nodes[0], we end up freeing
new_nodes[0] again. This was generating a lockdep warning. The fix is
to set new_nodes[0] to NULL, since the out_nocoalesce path safely
ignores NULL entries in the new_nodes array.

This regression was introduced in 2d7f9531.

Change-Id: I76564d7257800583214376b4bacf236cda90c89c
---

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index f8237856a61b..776583f7247d 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1409,6 +1409,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
 	BUG_ON(btree_bset_first(new_nodes[0])->keys);
 	btree_node_free(new_nodes[0]);
 	rw_unlock(true, new_nodes[0]);
+	new_nodes[0] = NULL;
 
 	for (i = 0; i < nodes; i++) {
 		if (__bch_keylist_realloc(&keylist, bkey_u64s(&r[i].b->key)))