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pptp: dst_release sk_dst_cache in pptp_sock_destruct

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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: 00959ade36 ("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>
This commit is contained in:
Xin Long 2019-03-13 17:00:48 +08:00 committed by David S. Miller
parent 63b6c974c2
commit 9417d81f4f
1 changed files with 1 additions and 0 deletions
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1
drivers/net/ppp/pptp.c
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@ -532,6 +532,7 @@ static void pptp_sock_destruct(struct sock *sk)
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)