linux-kernel - Re: [PATCH] nfc: llcp: stop processing on LLCP_CLOSED in nfc_llcp_recv

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Message-ID: <07e506c9-21f7-4d4a-ada3-ad0004acf6fc@kernel.org>
Date: Wed, 17 Dec 2025 08:35:48 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Qianchang Zhao <pioooooooooip@...il.com>, Paolo Abeni
 <pabeni@...hat.com>, Jakub Kicinski <kuba@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Simon Horman <horms@...nel.org>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org, Zhitong Liu <liuzhitong1993@...il.com>
Subject: Re: [PATCH] nfc: llcp: stop processing on LLCP_CLOSED in
 nfc_llcp_recv_hdlc()

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@...il.com>
> Reported-by: Zhitong Liu <liuzhitong1993@...il.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@...r.kernel.org
> Signed-off-by: Qianchang Zhao <pioooooooooip@...il.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