bcache: Fix __bch_btree_node_alloc to make the failure behavior consistent

In some specific situations, the return value of __bch_btree_node_alloc
may be NULL. This may lead to a potential NULL pointer dereference in
caller function like a calling chain :
btree_split->bch_btree_node_alloc->__bch_btree_node_alloc.

Fix it by initializing the return value in __bch_btree_node_alloc.

Fixes: cafe56359144 ("bcache: A block layer cache")
Cc: stable@vger.kernel.org
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Signed-off-by: Coly Li <colyli@suse.de>
Link: https://lore.kernel.org/r/20230615121223.22502-6-colyli@suse.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 7c21e54468bfd5daae919ad695c815cf89e0d3fe..0ddf91204782ded045403bf79ef0f6af5c30c834 100644 (file)
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1090,10 +1090,12 @@ struct btree *__bch_btree_node_alloc(struct cache_set *c, struct btree_op *op,
                                     struct btree *parent)
 {
        BKEY_PADDED(key) k;
-       struct btree *b = ERR_PTR(-EAGAIN);
+       struct btree *b;
 
        mutex_lock(&c->bucket_lock);
 retry:
+       /* return ERR_PTR(-EAGAIN) when it fails */
+       b = ERR_PTR(-EAGAIN);
        if (__bch_bucket_alloc_set(c, RESERVE_BTREE, &k.key, wait))
                goto err;