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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , oe-linux-nfc@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Yuchao Zhang Subject: [PATCH 1/1] nfc: llcp: reject connect() on sockets not in LLCP_CLOSED state Date: Fri, 18 Sep 2026 11:39:20 +0800 Message-ID: <20260918033920.85025-2-ndaugoing@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260918033920.85025-1-ndaugoing@gmail.com> References: <20260918033920.85025-1-ndaugoing@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When a socket is bound via llcp_sock_bind(), its state transitions to LLCP_BOUND and it is linked into the local->sockets hlist via nfc_llcp_sock_link(). Currently, llcp_sock_connect() only checks if the socket is already connected (LLCP_CONNECTED) or in progress (LLCP_CONNECTING): if (sk->sk_state == LLCP_CONNECTED) { ret = -EISCONN; goto error; } if (sk->sk_state == LLCP_CONNECTING) { ret = -EINPROGRESS; goto error; } Crucially, it does not check for the LLCP_BOUND (or LLCP_LISTEN) state. Previous fixes addressing CVE-2020-25670 / CVE-2020-25673 added the check for LLCP_CONNECTING to prevent duplicate in-flight connection attempts from corrupting the connecting_sockets list. However, they assumed any other non-connected socket was in LLCP_CLOSED, leaving the LLCP_BOUND state window unhandled. If connect() is invoked on a socket that has already been bound: 1. llcp_sock_connect() silently overwrites llcp_sock->dev and llcp_sock->local without releasing previous references or freeing the bound service_name, leading to refcount and memory leaks. 2. The socket remains linked in local->sockets, while llcp_sock_connect() links it again into local->connecting_sockets via nfc_llcp_sock_link(). 3. When connection confirmation (CC) arrives, nfc_llcp_recv_cc() executes: nfc_llcp_sock_unlink(&local->connecting_sockets, sk); nfc_llcp_sock_link(&local->sockets, sk); Because sk was never unlinked from local->sockets, the head.first of local->sockets still points to &sk->sk_node. The second hlist_add_head() sets sk->sk_node.next = sk->sk_node, producing a self-referential loop. Subsequent traversals of local->sockets (e.g. nfc_llcp_sock_get(), nfc_llcp_socket_release()) enter an infinite loop with spinlocks held, resulting in kernel soft-lockups. 4. Furthermore, if connect() specifies a different NFC device index than bind(), the socket remains linked on device A's socket list while being assigned to device B, causing cross-device socket confusion. Fix this by ensuring that llcp_sock_connect() only accepts sockets in the LLCP_CLOSED state, returning -EBADFD otherwise, matching the state check behavior in llcp_sock_bind(). Fixes: d646960f7986 ("NFC: Initial LLCP support") Signed-off-by: Yuchao Zhang --- net/nfc/llcp_sock.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c index 5558d8a4d48b..66f12e9af2fd 100644 --- a/net/nfc/llcp_sock.c +++ b/net/nfc/llcp_sock.c @@ -689,6 +689,10 @@ static int llcp_sock_connect(struct socket *sock, struct sockaddr_unsized *_addr ret = -EINPROGRESS; goto error; } + if (sk->sk_state != LLCP_CLOSED) { + ret = -EBADFD; + goto error; + } dev = nfc_get_device(addr->dev_idx); if (dev == NULL) { -- 2.53.0