[PATCH 5.15 188/917] Bluetooth: call sock_hold earlier in sco_conn_del

Greg Kroah-Hartman
2021-11-15T23:32:57Z

From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.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@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.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