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Sat, 12 Sep 2026 20:09:46 -0700 (PDT) Received: from MacBook-Pro ([2605:8300:17:166:1ca:862b:e953:e8d]) by smtp.gmail.com with ESMTPSA id af79cd13be357-939fc4a9455sm427688985a.31.2026.09.12.20.09.46 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 12 Sep 2026 20:09:46 -0700 (PDT) From: Juan Perdomo To: Marcel Holtmann , Luiz Augusto von Dentz Cc: linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+0cece8fa7d83523f47a3@syzkaller.appspotmail.com, Juan Perdomo Subject: [PATCH v2] Bluetooth: RFCOMM: avoid socket lock inversion in listener cleanup Date: Sat, 12 Sep 2026 23:09:45 -0400 Message-ID: <20260913030945.4011-1-jcperdomo100@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <6aa2d63e.6e6c5f9e.28f11f.0036.GAE@google.com> References: <6aa2d63e.6e6c5f9e.28f11f.0036.GAE@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit rfcomm_sock_cleanup_listen() closes unaccepted child sockets through rfcomm_sock_close(), which takes the child socket lock before rfcomm_dlc_close() acquires rfcomm_mutex. The RFCOMM worker takes these locks in reverse order while handling connections and DLC state changes, so lockdep reports a possible deadlock. Close dequeued children without taking their socket lock. The accept queue owns a reference to each child, and bt_accept_dequeue() locks the child while unlinking it and clearing its parent pointer. Dropping the child lock makes it important to prevent a concurrent rfcomm_connect_ind() from enqueueing a new child after cleanup observes an empty queue. Set a listening socket to BT_CLOSED while its lock is still held, before dropping the lock and draining the queue. The state check in rfcomm_connect_ind() then rejects new children once cleanup starts. Reported-by: syzbot+0cece8fa7d83523f47a3@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=0cece8fa7d83523f47a3 Fixes: b7ce436a5d79 ("Bluetooth: switch to lock_sock in RFCOMM") Signed-off-by: Juan Perdomo --- Changes in v2: - Mark the listener BT_CLOSED under its socket lock before accept-queue cleanup, preventing new children from racing with teardown. - Retest with syzbot after its v1 run exposed the accept-queue race. The revised patch completed without triggering an issue: https://syzkaller.appspot.com/x/bisect.txt?x=156ca925580000 net/bluetooth/rfcomm/sock.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c index 958081adb..e2486bc11 100644 --- a/net/bluetooth/rfcomm/sock.c +++ b/net/bluetooth/rfcomm/sock.c @@ -242,9 +242,7 @@ static void __rfcomm_sock_close(struct sock *sk) */ static void rfcomm_sock_close(struct sock *sk) { - lock_sock(sk); __rfcomm_sock_close(sk); - release_sock(sk); } static void rfcomm_sock_init(struct sock *sk, struct sock *parent) @@ -905,6 +903,7 @@ static int rfcomm_sock_compat_ioctl(struct socket *sock, unsigned int cmd, unsig static int rfcomm_sock_shutdown(struct socket *sock, int how) { struct sock *sk = sock->sk; + bool cleanup_listen = false; int err = 0; BT_DBG("sock %p, sk %p", sock, sk); @@ -915,9 +914,17 @@ static int rfcomm_sock_shutdown(struct socket *sock, int how) lock_sock(sk); if (!sk->sk_shutdown) { sk->sk_shutdown = SHUTDOWN_MASK; + if (sk->sk_state == BT_LISTEN) { + /* Block new children before cleaning up without sk lock. */ + sk->sk_state = BT_CLOSED; + cleanup_listen = true; + } release_sock(sk); - __rfcomm_sock_close(sk); + if (cleanup_listen) + rfcomm_sock_cleanup_listen(sk); + else + __rfcomm_sock_close(sk); lock_sock(sk); if (sock_flag(sk, SOCK_LINGER) && sk->sk_lingertime && -- 2.50.1 (Apple Git-155)