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[107.146.107.67]) by smtp.gmail.com with ESMTPSA id a1e0cc1a2514c-80f728caa7bsm1261336241.12.2024.06.24.06.46.38 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Jun 2024 06:46:39 -0700 (PDT) From: Luiz Augusto von Dentz To: linux-bluetooth@vger.kernel.org Subject: [PATCH v1] Bluetooth: L2CAP: Fix deadlock Date: Mon, 24 Jun 2024 09:46:37 -0400 Message-ID: <20240624134637.3790278-1-luiz.dentz@gmail.com> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-bluetooth@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Luiz Augusto von Dentz This fixes the following deadlock introduced by e3203b177717 ("bluetooth/l2cap: sync sock recv cb and release"): ============================================ WARNING: possible recursive locking detected 6.10.0-rc3-g4029dba6b6f1 #6823 Not tainted -------------------------------------------- kworker/u5:0/35 is trying to acquire lock: ffff888002ec2510 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_sock_recv_cb+0x44/0x1e0 but task is already holding lock: ffff888002ec2510 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_get_chan_by_scid+0xaf/0xd0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&chan->lock#2/1); lock(&chan->lock#2/1); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by kworker/u5:0/35: #0: ffff888002b8a940 ((wq_completion)hci0#2){+.+.}-{0:0}, at: process_one_work+0x750/0x930 #1: ffff888002c67dd0 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_one_work+0x44e/0x930 #2: ffff888002ec2510 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_get_chan_by_scid+0xaf/0xd0 To fix the original problem this introduces l2cap_chan_lock at l2cap_conless_channel to ensure that l2cap_sock_recv_cb is called with chan->lock held. Fixes: e3203b177717 ("bluetooth/l2cap: sync sock recv cb and release") Signed-off-by: Luiz Augusto von Dentz --- net/bluetooth/l2cap_core.c | 3 +++ net/bluetooth/l2cap_sock.c | 13 +------------ 2 files changed, 4 insertions(+), 12 deletions(-) diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index aed025734d04..c3c26bbb5dda 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -6761,6 +6761,8 @@ static void l2cap_conless_channel(struct l2cap_conn *conn, __le16 psm, BT_DBG("chan %p, len %d", chan, skb->len); + l2cap_chan_lock(chan); + if (chan->state != BT_BOUND && chan->state != BT_CONNECTED) goto drop; @@ -6777,6 +6779,7 @@ static void l2cap_conless_channel(struct l2cap_conn *conn, __le16 psm, } drop: + l2cap_chan_unlock(chan); l2cap_chan_put(chan); free_skb: kfree_skb(skb); diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index 962aa11ce3de..ba437c6f6ee5 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -1489,18 +1489,9 @@ static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb) struct l2cap_pinfo *pi; int err; - /* To avoid race with sock_release, a chan lock needs to be added here - * to synchronize the sock. - */ - l2cap_chan_hold(chan); - l2cap_chan_lock(chan); sk = chan->data; - - if (!sk) { - l2cap_chan_unlock(chan); - l2cap_chan_put(chan); + if (!sk) return -ENXIO; - } pi = l2cap_pi(sk); lock_sock(sk); @@ -1552,8 +1543,6 @@ static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb) done: release_sock(sk); - l2cap_chan_unlock(chan); - l2cap_chan_put(chan); return err; }