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tcp: fix potential double free issue for fastopen_req

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tp->fastopen_req could potentially be double freed if a malicious
user does the following:
1. Enable TCP_FASTOPEN_CONNECT sockopt and do a connect() on the socket.
2. Call connect() with AF_UNSPEC to disconnect the socket.
3. Make this socket a listening socket by calling listen().
4. Accept incoming connections and generate child sockets. All child
   sockets will get a copy of the pointer of fastopen_req.
5. Call close() on all sockets. fastopen_req will get freed multiple
   times.

Fixes: 19f6d3f3c8 ("net/tcp-fastopen: Add new API support")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Wei Wang <weiwan@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Wei Wang 2017-03-01 13:29:48 -08:00 committed by David S. Miller
parent 94352d4509
commit 7db92362d2
1 changed files with 12 additions and 3 deletions
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15
net/ipv4/tcp.c
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@ -1110,9 +1110,14 @@ static int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg,
flags = (msg->msg_flags & MSG_DONTWAIT) ? O_NONBLOCK : 0;
err = __inet_stream_connect(sk->sk_socket, msg->msg_name,
msg->msg_namelen, flags, 1);
inet->defer_connect = 0;
*copied = tp->fastopen_req->copied;
tcp_free_fastopen_req(tp);
/* fastopen_req could already be freed in __inet_stream_connect
* if the connection times out or gets rst
*/
if (tp->fastopen_req) {
*copied = tp->fastopen_req->copied;
tcp_free_fastopen_req(tp);
inet->defer_connect = 0;
}
return err;
}
@ -2318,6 +2323,10 @@ int tcp_disconnect(struct sock *sk, int flags)
memset(&tp->rx_opt, 0, sizeof(tp->rx_opt));
__sk_dst_reset(sk);
/* Clean up fastopen related fields */
tcp_free_fastopen_req(tp);
inet->defer_connect = 0;
WARN_ON(inet->inet_num && !icsk->icsk_bind_hash);
sk->sk_error_report(sk);