[PATCH AUTOSEL 6.0 71/77] Bluetooth: L2CAP: Fix user-after-free

Sasha Levin
2022-10-09T22:25:10Z

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

[ Upstream commit 35fcbc4243aad7e7d020b7c1dfb14bb888b20a4f ]

This uses l2cap_chan_hold_unless_zero() after calling
__l2cap_get_chan_blah() to prevent the following trace:

Bluetooth: l2cap_core.c:static void l2cap_chan_destroy(struct kref
*kref)
Bluetooth: chan 0000000023c4974d
Bluetooth: parent 00000000ae861c08
==================================================================
BUG: KASAN: use-after-free in __mutex_waiter_is_first
kernel/locking/mutex.c:191 [inline]
BUG: KASAN: use-after-free in __mutex_lock_common
kernel/locking/mutex.c:671 [inline]
BUG: KASAN: use-after-free in __mutex_lock+0x278/0x400
kernel/locking/mutex.c:729
Read of size 8 at addr ffff888006a49b08 by task kworker/u3:2/389

Link: https://lore.kernel.org/lkml/20220622082716.478486-1-lee.jones@linaro.org
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sungwoo Kim <iam@sung-woo.kim>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/bluetooth/l2cap_core.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 770891f68703..1f34b82ca0ec 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -4309,6 +4309,12 @@ static int l2cap_connect_create_rsp(struct l2cap_conn *conn,
}
}

+ chan = l2cap_chan_hold_unless_zero(chan);
+ if (!chan) {
+ err = -EBADSLT;
+ goto unlock;
+ }
+
err = 0;

l2cap_chan_lock(chan);
@@ -4338,6 +4344,7 @@ static int l2cap_connect_create_rsp(struct l2cap_conn *conn,
}

l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);

unlock:
mutex_unlock(&conn->chan_lock);
--
2.35.1