linux-kernel - Re: [RESEND PATCH v3] bcache: Fix __bch_btree_node_alloc to make the failure behavior consistent

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Date:   Sat, 18 Feb 2023 23:22:26 +0800
From:   Coly Li <colyli@...e.de>
To:     Zheng Wang <zyytlz.wz@....com>
Cc:     Zheng Hacker <hackerzheng666@...il.com>, kent.overstreet@...il.com,
        linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org,
        alex000young@...il.com, stable@...r.kernel.org
Subject: Re: [RESEND PATCH v3] bcache: Fix __bch_btree_node_alloc to make the
 failure  behavior consistent

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@...r.kernel.org
> Signed-off-by: Zheng Wang <zyytlz.wz@....com>

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

Coly Li

> ---
> v3:
> - Add Cc: stable@...r.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
>