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authorWei Wang <weiwan@google.com>2017-03-01 13:29:48 -0800
committerDavid S. Miller <davem@davemloft.net>2017-03-02 14:05:41 -0800
commit7db92362d2fee5887f6b0c41653b8c9f8f5d6020 (patch)
tree4d1b45575d0b490061671c4dddaa32f795013e59
parent94352d45092c23874532221b4d1e4721df9d63df (diff)
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 times. Fixes: 19f6d3f3c842 ("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>
-rw-r--r--net/ipv4/tcp.c15
1 files changed, 12 insertions, 3 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index da385ae..cf45555 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -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);