[PATCH v2 2/2 5.10.y] Bluetooth: SCO: Fix use-after-free in sco_recv_frame() due to missing sock_hold

[Todd Kjos <tkjos@google.com>]

From: Hyunwoo Kim <imv4bel@gmail.com>

[ Upstream commit 598dbba9919c5e36c54fe1709b557d64120cb94b ]

sco_recv_frame() reads conn->sk under sco_conn_lock() but immediately
releases the lock without holding a reference to the socket. A concurrent
close() can free the socket between the lock release and the subsequent
sk->sk_state access, resulting in a use-after-free.

Other functions in the same file (sco_sock_timeout(), sco_conn_del())
correctly use sco_sock_hold() to safely hold a reference under the lock.

Fix by using sco_sock_hold() to take a reference before releasing the
lock, and adding sock_put() on all exit paths.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Todd Kjos <tkjos@google.com>
---
 net/bluetooth/sco.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index 2fbd9c93440ce4936d47b3bd47aa1dc28da82c20..b49b2d6bb778e8956d4a297c9feecadd1557a3b9 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -312,7 +312,7 @@ static void sco_recv_frame(struct sco_conn *conn, struct sk_buff *skb)
 	struct sock *sk;
 
 	sco_conn_lock(conn);
-	sk = conn->sk;
+	sk = sco_sock_hold(conn);
 	sco_conn_unlock(conn);
 
 	if (!sk)
@@ -321,11 +321,15 @@ static void sco_recv_frame(struct sco_conn *conn, struct sk_buff *skb)
 	BT_DBG("sk %p len %d", sk, skb->len);
 
 	if (sk->sk_state != BT_CONNECTED)
-		goto drop;
+		goto drop_put;
 
-	if (!sock_queue_rcv_skb(sk, skb))
+	if (!sock_queue_rcv_skb(sk, skb)) {
+		sock_put(sk);
 		return;
+	}
 
+drop_put:
+	sock_put(sk);
 drop:
 	kfree_skb(skb);
 }
-- 
2.55.0.629.g250fe7f194-goog