From: Hillf Danton hdanton@sina.com
[ Upstream commit 2a154903cec20fb64ff4d7d617ca53c16f8fd53a ]
Prefetch channel before killing sock in order to fix UAF like
BUG: KASAN: use-after-free in l2cap_sock_release+0x24c/0x290 net/bluetooth/l2cap_sock.c:1212 Read of size 8 at addr ffff8880944904a0 by task syz-fuzzer/9751
Reported-by: syzbot+c3c5bdea7863886115dc@syzkaller.appspotmail.com Fixes: 6c08fc896b60 ("Bluetooth: Fix refcount use-after-free issue") Cc: Manish Mandlik mmandlik@google.com Signed-off-by: Hillf Danton hdanton@sina.com Signed-off-by: Marcel Holtmann marcel@holtmann.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/bluetooth/l2cap_sock.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index a5e618add17f4..511a1da6ca971 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -1191,6 +1191,7 @@ static int l2cap_sock_release(struct socket *sock) { struct sock *sk = sock->sk; int err; + struct l2cap_chan *chan;
BT_DBG("sock %p, sk %p", sock, sk);
@@ -1200,15 +1201,16 @@ static int l2cap_sock_release(struct socket *sock) bt_sock_unlink(&l2cap_sk_list, sk);
err = l2cap_sock_shutdown(sock, 2); + chan = l2cap_pi(sk)->chan;
- l2cap_chan_hold(l2cap_pi(sk)->chan); - l2cap_chan_lock(l2cap_pi(sk)->chan); + l2cap_chan_hold(chan); + l2cap_chan_lock(chan);
sock_orphan(sk); l2cap_sock_kill(sk);
- l2cap_chan_unlock(l2cap_pi(sk)->chan); - l2cap_chan_put(l2cap_pi(sk)->chan); + l2cap_chan_unlock(chan); + l2cap_chan_put(chan);
return err; }