linux-kernel - [PATCH AUTOSEL 5.15 007/146] Bluetooth: call sock_hold earlier in sco_conn

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Date:   Mon,  8 Nov 2021 12:42:34 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>,
        Luiz Augusto von Dentz <luiz.von.dentz@...el.com>,
        Sasha Levin <sashal@...nel.org>, marcel@...tmann.org,
        johan.hedberg@...il.com, luiz.dentz@...il.com, davem@...emloft.net,
        kuba@...nel.org, linux-bluetooth@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 007/146] Bluetooth: call sock_hold earlier in sco_conn_del

From: Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>

[ Upstream commit f4712fa993f688d0a48e0c28728fcdeb88c1ea58 ]

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@...il.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 b62c91c627e2c..4a057f99b60aa 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);
-- 
2.33.0