nfc: llcp: stop processing on LLCP_CLOSED in nfc_llcp_recv_hdlc()

[PATCH] nfc: llcp: stop processing on LLCP_CLOSED in nfc_llcp_recv_hdlc()

Posted by Qianchang Zhao 1 day, 12 hours ago

nfc_llcp_sock_get() takes a reference on the LLCP socket via sock_hold().

In nfc_llcp_recv_hdlc(), the LLCP_CLOSED branch releases the socket lock and
drops the reference, but the function continues to operate on llcp_sock/sk and
later runs release_sock() and nfc_llcp_sock_put() again on the common exit path.

Return immediately after the CLOSED cleanup to avoid refcount/lock imbalance and
to avoid using the socket after dropping the reference.

Reported-by: Qianchang Zhao <pioooooooooip@gmail.com>
Reported-by: Zhitong Liu <liuzhitong1993@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Qianchang Zhao <pioooooooooip@gmail.com>
---
 net/nfc/llcp_core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c
index beeb3b4d2..be01ec9f4 100644
--- a/net/nfc/llcp_core.c
+++ b/net/nfc/llcp_core.c
@@ -1089,6 +1089,7 @@ static void nfc_llcp_recv_hdlc(struct nfc_llcp_local *local,
 	if (sk->sk_state == LLCP_CLOSED) {
 		release_sock(sk);
 		nfc_llcp_sock_put(llcp_sock);
+		return;
 	}
 
 	/* Pass the payload upstream */
-- 
2.34.1

Re: [PATCH] nfc: llcp: stop processing on LLCP_CLOSED in nfc_llcp_recv_hdlc()

Posted by Krzysztof Kozlowski 1 day, 6 hours ago

On 17/12/2025 02:15, Qianchang Zhao wrote:
> nfc_llcp_sock_get() takes a reference on the LLCP socket via sock_hold().
> 
> In nfc_llcp_recv_hdlc(), the LLCP_CLOSED branch releases the socket lock and
> drops the reference, but the function continues to operate on llcp_sock/sk and
> later runs release_sock() and nfc_llcp_sock_put() again on the common exit path.
> 
> Return immediately after the CLOSED cleanup to avoid refcount/lock imbalance and
> to avoid using the socket after dropping the reference.
> 
> Reported-by: Qianchang Zhao <pioooooooooip@gmail.com>
> Reported-by: Zhitong Liu <liuzhitong1993@gmail.com>

No, drop. Same comments as for other patch.

Organize your patches in a patchset. Don't send independent works, it's
just more work for maintainers to apply.


> Cc: stable@vger.kernel.org
> Signed-off-by: Qianchang Zhao <pioooooooooip@gmail.com>
> ---
>  net/nfc/llcp_core.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c
> index beeb3b4d2..be01ec9f4 100644
> --- a/net/nfc/llcp_core.c
> +++ b/net/nfc/llcp_core.c
> @@ -1089,6 +1089,7 @@ static void nfc_llcp_recv_hdlc(struct nfc_llcp_local *local,
>  	if (sk->sk_state == LLCP_CLOSED) {
>  		release_sock(sk);
>  		nfc_llcp_sock_put(llcp_sock);
> +		return;

Answer my previous questions from the private thread.

>  	}
>  
>  	/* Pass the payload upstream */


Best regards,
Krzysztof