Bluetooth: call sock_hold earlier in sco_conn_del

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>

diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index b62c91c627e2c955900f98de1ce2663aa2e77120..4a057f99b60aac76fb04cc121c2026d3cfa8c9ee 100644 (file)
--- 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);