4.4-stable review patch. If anyone has any objections, please let me know.
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From: Xin Long lucien.xin@gmail.com
[ Upstream commit 9417d81f4f8adfe20a12dd1fadf73a618cbd945d ]
sk_setup_caps() is called to set sk->sk_dst_cache in pptp_connect, so we have to dst_release(sk->sk_dst_cache) in pptp_sock_destruct, otherwise, the dst refcnt will leak.
It can be reproduced by this syz log:
r1 = socket$pptp(0x18, 0x1, 0x2) bind$pptp(r1, &(0x7f0000000100)={0x18, 0x2, {0x0, @local}}, 0x1e) connect$pptp(r1, &(0x7f0000000000)={0x18, 0x2, {0x3, @remote}}, 0x1e)
Consecutive dmesg warnings will occur:
unregister_netdevice: waiting for lo to become free. Usage count = 1
v1->v2: - use rcu_dereference_protected() instead of rcu_dereference_check(), as suggested by Eric.
Fixes: 00959ade36ac ("PPTP: PPP over IPv4 (Point-to-Point Tunneling Protocol)") Reported-by: Xiumei Mu xmu@redhat.com Signed-off-by: Xin Long lucien.xin@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/ppp/pptp.c | 1 + 1 file changed, 1 insertion(+)
--- a/drivers/net/ppp/pptp.c +++ b/drivers/net/ppp/pptp.c @@ -577,6 +577,7 @@ static void pptp_sock_destruct(struct so pppox_unbind_sock(sk); } skb_queue_purge(&sk->sk_receive_queue); + dst_release(rcu_dereference_protected(sk->sk_dst_cache, 1)); }
static int pptp_create(struct net *net, struct socket *sock, int kern)