[PATCH 6.1 105/137] Bluetooth: SCO: Fix UAF on sco_sock_timeout

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

[ Upstream commit 1bf4470a3939c678fb822073e9ea77a0560bc6bb ]

conn->sk maybe have been unlinked/freed while waiting for sco_conn_lock
so this checks if the conn->sk is still valid by checking if it part of
sco_sk_list.

Reported-by: syzbot+4c0d0c4cde787116d465@syzkaller.appspotmail.com
Tested-by: syzbot+4c0d0c4cde787116d465@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=4c0d0c4cde787116d465
Fixes: ba316be1b6a0 ("Bluetooth: schedule SCO timeouts with delayed_work")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/net/bluetooth/bluetooth.h |  1 +
 net/bluetooth/af_bluetooth.c      | 22 ++++++++++++++++++++++
 net/bluetooth/sco.c               | 18 ++++++++++++------
 3 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
index c7f1dd34ea470..41fc7f12971a5 100644
--- a/include/net/bluetooth/bluetooth.h
+++ b/include/net/bluetooth/bluetooth.h
@@ -383,6 +383,7 @@ int  bt_sock_register(int proto, const struct net_proto_family *ops);
 void bt_sock_unregister(int proto);
 void bt_sock_link(struct bt_sock_list *l, struct sock *s);
 void bt_sock_unlink(struct bt_sock_list *l, struct sock *s);
+bool bt_sock_linked(struct bt_sock_list *l, struct sock *s);
 struct sock *bt_sock_alloc(struct net *net, struct socket *sock,
 			   struct proto *prot, int proto, gfp_t prio, int kern);
 int  bt_sock_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c
index 0c70172555b4f..4c3bd05160387 100644
--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -177,6 +177,28 @@ void bt_sock_unlink(struct bt_sock_list *l, struct sock *sk)
 }
 EXPORT_SYMBOL(bt_sock_unlink);
 
+bool bt_sock_linked(struct bt_sock_list *l, struct sock *s)
+{
+	struct sock *sk;
+
+	if (!l || !s)
+		return false;
+
+	read_lock(&l->lock);
+
+	sk_for_each(sk, &l->head) {
+		if (s == sk) {
+			read_unlock(&l->lock);
+			return true;
+		}
+	}
+
+	read_unlock(&l->lock);
+
+	return false;
+}
+EXPORT_SYMBOL(bt_sock_linked);
+
 void bt_accept_enqueue(struct sock *parent, struct sock *sk, bool bh)
 {
 	BT_DBG("parent %p, sk %p", parent, sk);
diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index 92ea01f9def3e..ad5afde17213a 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -77,6 +77,16 @@ struct sco_pinfo {
 #define SCO_CONN_TIMEOUT	(HZ * 40)
 #define SCO_DISCONN_TIMEOUT	(HZ * 2)
 
+static struct sock *sco_sock_hold(struct sco_conn *conn)
+{
+	if (!conn || !bt_sock_linked(&sco_sk_list, conn->sk))
+		return NULL;
+
+	sock_hold(conn->sk);
+
+	return conn->sk;
+}
+
 static void sco_sock_timeout(struct work_struct *work)
 {
 	struct sco_conn *conn = container_of(work, struct sco_conn,
@@ -88,9 +98,7 @@ static void sco_sock_timeout(struct work_struct *work)
 		sco_conn_unlock(conn);
 		return;
 	}
-	sk = conn->sk;
-	if (sk)
-		sock_hold(sk);
+	sk = sco_sock_hold(conn);
 	sco_conn_unlock(conn);
 
 	if (!sk)
@@ -195,9 +203,7 @@ 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);
+	sk = sco_sock_hold(conn);
 	sco_conn_unlock(conn);
 
 	if (sk) {
-- 
2.43.0