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Date: Thu, 2 Feb 2023 04:05:10 -0500
From: Sungwoo Kim <iam@...g-woo.kim>
To: happiness.sung.woo@...il.com
Cc: benquike@...il.com, davem@...emloft.net, daveti@...due.edu,
edumazet@...gle.com, johan.hedberg@...il.com, kuba@...nel.org,
linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
luiz.dentz@...il.com, marcel@...tmann.org, netdev@...r.kernel.org,
pabeni@...hat.com, wuruoyu@...com, Sungwoo Kim <iam@...g-woo.kim>
Subject: [PATCH] Bluetooth: L2CAP: Fix use-after-free
Due to the race condition between l2cap_sock_cleanup_listen and
l2cap_sock_close_cb, l2cap_sock_kill can receive already freed sk,
resulting in use-after-free inside l2cap_sock_kill.
This patch prevent this by adding a null check in l2cap_sock_kill.
Context 1:
l2cap_sock_cleanup_listen();
// context switched
l2cap_chan_lock(chan);
l2cap_sock_kill(sk); // <-- sk is already freed below
Context 2:
l2cap_chan_timeout();
l2cap_chan_lock(chan);
chan->ops->close(chan);
l2cap_sock_close_cb()
l2cap_sock_kill(sk); // <-- sk is freed here
l2cap_chan_unlock(chan);
Signed-off-by: Sungwoo Kim <iam@...g-woo.kim>
---
net/bluetooth/l2cap_sock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index ca8f07f35..657704059 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -1245,7 +1245,7 @@ static int l2cap_sock_recvmsg(struct socket *sock, struct msghdr *msg,
*/
static void l2cap_sock_kill(struct sock *sk)
{
- if (!sock_flag(sk, SOCK_ZAPPED) || sk->sk_socket)
+ if (!sk || !sock_flag(sk, SOCK_ZAPPED) || sk->sk_socket)
return;
BT_DBG("sk %p state %s", sk, state_to_string(sk->sk_state));
--
2.25.1
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