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From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
To: marcel@holtmann.org, johan.hedberg@gmail.com,
	luiz.dentz@gmail.com, davem@davemloft.net, kuba@kernel.org
Cc: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>,
	linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, eric.dumazet@gmail.com
Subject: [PATCH 1/2] Bluetooth: call sock_hold earlier in sco_conn_del
Date: Thu,  2 Sep 2021 23:13:05 -0400	[thread overview]
Message-ID: <20210903031306.78292-2-desmondcheongzx@gmail.com> (raw)
In-Reply-To: <20210903031306.78292-1-desmondcheongzx@gmail.com>

In sco_conn_del, conn->sk is read while holding on to the
sco_conn.lock to avoid races with a socket that could be released
concurrently.

However, in between unlocking sco_conn.lock and calling sock_hold,
it's possible for the socket to be freed, which would cause a
use-after-free write when sock_hold is finally called.

To fix this, the reference count of the socket should be increased
while the sco_conn.lock is still held.

Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
---
 net/bluetooth/sco.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index b62c91c627e2..4a057f99b60a 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -187,10 +187,11 @@ static void sco_conn_del(struct hci_conn *hcon, int err)
 	/* Kill socket */
 	sco_conn_lock(conn);
 	sk = conn->sk;
+	if (sk)
+		sock_hold(sk);
 	sco_conn_unlock(conn);
 
 	if (sk) {
-		sock_hold(sk);
 		lock_sock(sk);
 		sco_sock_clear_timer(sk);
 		sco_chan_del(sk, err);
-- 
2.25.1


  reply	other threads:[~2021-09-03  3:23 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-03  3:13 [PATCH 0/2] Bluetooth: various SCO fixes Desmond Cheong Zhi Xi
2021-09-03  3:13 ` Desmond Cheong Zhi Xi [this message]
2021-09-10  7:36   ` [PATCH 1/2] Bluetooth: call sock_hold earlier in sco_conn_del Marcel Holtmann
2021-10-04 18:12     ` Desmond Cheong Zhi Xi
2021-09-03  3:13 ` [PATCH 2/2] Bluetooth: fix init and cleanup of sco_conn.timeout_work Desmond Cheong Zhi Xi
2021-09-03 23:37 ` [PATCH 0/2] Bluetooth: various SCO fixes Luiz Augusto von Dentz

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