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(unknown [36.110.52.2]) by APP-01 (Coremail) with SMTP id qwCowAB3GNFd8xhqkJUWAA--.4625S2; Fri, 29 May 2026 10:01:01 +0800 (CST) From: Jiakai Xu To: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Cc: "David S . Miller" , Breno Leitao , Eric Dumazet , Ernestas Kulik , Jakub Kicinski , Jiakai Xu , Kees Cook , Kuniyuki Iwashima , Paolo Abeni , Simon Horman Subject: [PATCH v2] llc: Fix race between sock_orphan() and timer callback in llc_sk_free() Date: Fri, 29 May 2026 02:00:59 +0000 Message-Id: <20260529020059.3024038-1-xujiakai24@mails.ucas.ac.cn> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: qwCowAB3GNFd8xhqkJUWAA--.4625S2 X-Coremail-Antispam: 1UD129KBjvJXoW7ZFW3WFyfCrWfZrWxZF1DJrb_yoW8Zw4UpF 45CFy7KFyqvrZIvFWftF1kGrn3Xan3K3y7CrWDCr4fuwn8Jr15K34rt3yq9Fs0yFs5Cry3 Jr4kWr4rCa1kZaDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUBI14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26F1j6w1UM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26F4j 6r4UJwA2z4x0Y4vEx4A2jsIE14v26F4UJVW0owA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Cr 1j6rxdM2vYz4IE04k24VAvwVAKI4IrM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVAC Y4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJV W8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41lF7I21c0EjII2zVCS5cI2 0VAGYxC7M4IIrI8v6xkF7I0E8cxan2IY04v7MxkF7I0En4kS14v26r1q6r43MxAIw28Icx kI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2Iq xVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI42 IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AKxVW8JVWxJwCI42IY 6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2z280aV CY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7VUbQVy7UUUUU== X-CM-SenderInfo: 50xmxthndljko6pdxz3voxutnvoduhdfq/ Content-Type: text/plain; charset="utf-8" In llc_ui_release(), sock_orphan() was called before llc_sk_free() stopped all LLC timers. A pending timer callback (llc_conn_ack_tmr_cb()->llc_process_tmr_ev()->llc_conn_state_process()) could fire between these two operations and dereference the NULL sk->sk_socket that sock_orphan() sets, causing a kernel page fault. Fix the race by moving sock_orphan() into llc_sk_free(), after llc_sk_stop_all_timers() has completed. This guarantees that all timers are stopped before the socket is orphaned, eliminating the window for the race. Fixes: aa2b2eb39348 ("llc: call sock_orphan() at release time") Signed-off-by: Jiakai Xu --- V1 -> V2: - Replaced sk->sk_socket NULL checks with moving sock_orphan() after timer stop, as suggested by Paolo Abeni. Link: https://lore.kernel.org/lkml/20260526013541.796307-1-xujiakai24@mails= .ucas.ac.cn/T/#u --- net/llc/af_llc.c | 1 - net/llc/llc_conn.c | 5 +++++ 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c index 35278c519a30..92f3576b339a 100644 --- a/net/llc/af_llc.c +++ b/net/llc/af_llc.c @@ -227,7 +227,6 @@ static int llc_ui_release(struct socket *sock) } netdev_put(llc->dev, &llc->dev_tracker); sock_put(sk); - sock_orphan(sk); sock->sk =3D NULL; llc_sk_free(sk); out: diff --git a/net/llc/llc_conn.c b/net/llc/llc_conn.c index 5c0ac243b248..c02285441592 100644 --- a/net/llc/llc_conn.c +++ b/net/llc/llc_conn.c @@ -977,6 +977,11 @@ void llc_sk_free(struct sock *sk) llc->state =3D LLC_CONN_OUT_OF_SVC; /* Stop all (possibly) running timers */ llc_sk_stop_all_timers(sk, true); + /* Orphan the socket after timers are stopped; otherwise a pending + * timer callback could dereference the NULL sk->sk_socket that + * sock_orphan() sets. + */ + sock_orphan(sk); #ifdef DEBUG_LLC_CONN_ALLOC printk(KERN_INFO "%s: unackq=3D%d, txq=3D%d\n", __func__, skb_queue_len(&llc->pdu_unack_q), --=20 2.34.1