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

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Message-Id: <20251217011538.16029-1-pioooooooooip@gmail.com>
Date: Wed, 17 Dec 2025 10:15:38 +0900
From: Qianchang Zhao <pioooooooooip@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
	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>,
	Qianchang Zhao <pioooooooooip@...il.com>
Subject: [PATCH] nfc: llcp: stop processing on LLCP_CLOSED in nfc_llcp_recv_hdlc()

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>
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;
 	}
 
 	/* Pass the payload upstream */
-- 
2.34.1