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

Fix it by initialize return value in __bch_btree_node_alloc before return.

Fixes: cafe56359144 ("bcache: A block layer cache")
Cc: stable@vger.kernel.org
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
---
v3:
- Add Cc: stable@vger.kernel.org suggested by Eric
v2:
- split patch v1 into two patches to make it clearer suggested by Coly Li
---
 drivers/md/bcache/btree.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 147c493a989a..cae25e74b9e0 100644
--- 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;
 
-- 
2.25.1

On Sat, Feb 18, 2023 at 03:23:35PM +0800, Zheng Wang wrote:
> In some specific situation, the return value of __bch_btree_node_alloc may
> be NULL. This may lead to poential NULL pointer dereference in caller
> function like a calling chaion :
> btree_split->bch_btree_node_alloc->__bch_btree_node_alloc.
> 
> Fix it by initialize return value in __bch_btree_node_alloc before return.
> 
> Fixes: cafe56359144 ("bcache: A block layer cache")
> Cc: stable@vger.kernel.org
> Signed-off-by: Zheng Wang <zyytlz.wz@163.com>

Thanks, I will add this series to my for-next testing queue.

Coly Li

> ---
> v3:
> - Add Cc: stable@vger.kernel.org suggested by Eric
> v2:
> - split patch v1 into two patches to make it clearer suggested by Coly Li
> ---
> drivers/md/bcache/btree.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
> index 147c493a989a..cae25e74b9e0 100644
> --- 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;
> 
> -- 
> 2.25.1
>