linux-kernel - [PATCH] nfc: llcp: avoid double release/put on LLCP_CLOSED in nfc_llcp_recv

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Message-Id: <20251217014048.16889-1-pioooooooooip@gmail.com>
Date: Wed, 17 Dec 2025 10:40:48 +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: avoid double release/put on LLCP_CLOSED in nfc_llcp_recv_disc()

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

In nfc_llcp_recv_disc(), when the socket is already in LLCP_CLOSED state, the
code used to perform release_sock() and nfc_llcp_sock_put() in the CLOSED branch
but then continued execution and later performed the same cleanup again on the
common exit path. This results in refcount imbalance (double put) and unbalanced
lock release.

Remove the redundant CLOSED-branch cleanup so that release_sock() and
nfc_llcp_sock_put() are performed exactly once via the common exit path, while
keeping the existing DM_DISC reply behavior.

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 | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c
index beeb3b4d2..ed37604ed 100644
--- a/net/nfc/llcp_core.c
+++ b/net/nfc/llcp_core.c
@@ -1177,11 +1177,6 @@ static void nfc_llcp_recv_disc(struct nfc_llcp_local *local,

 	nfc_llcp_socket_purge(llcp_sock);

-	if (sk->sk_state == LLCP_CLOSED) {
-		release_sock(sk);
-		nfc_llcp_sock_put(llcp_sock);
-	}
-
 	if (sk->sk_state == LLCP_CONNECTED) {
 		nfc_put_device(local->dev);
 		sk->sk_state = LLCP_CLOSED;
-- 
2.34.1