Commit 7db92362 authored by Wei Wang's avatar Wei Wang Committed by David S. Miller

tcp: fix potential double free issue for fastopen_req

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

Fixes: 19f6d3f3 ("net/tcp-fastopen: Add new API support")
Reported-by: default avatarAndrey Konovalov <[email protected]>
Signed-off-by: default avatarWei Wang <[email protected]>
Signed-off-by: default avatarEric Dumazet <[email protected]>
Signed-off-by: default avatarDavid S. Miller <[email protected]>
parent 94352d45
......@@ -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;
/* 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;
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));
/* Clean up fastopen related fields */
inet->defer_connect = 0;
WARN_ON(inet->inet_num && !icsk->icsk_bind_hash);
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