Commit bee47cb0 authored by Olga Kornievskaia's avatar Olga Kornievskaia Committed by Chuck Lever
Browse files

sunrpc: fix handling of server side tls alerts 



Scott Mayhew discovered a security exploit in NFS over TLS in
tls_alert_recv() due to its assumption it can read data from
the msg iterator's kvec..

kTLS implementation splits TLS non-data record payload between
the control message buffer (which includes the type such as TLS
aler or TLS cipher change) and the rest of the payload (say TLS
alert's level/description) which goes into the msg payload buffer.

This patch proposes to rework how control messages are setup and
used by sock_recvmsg().

If no control message structure is setup, kTLS layer will read and
process TLS data record types. As soon as it encounters a TLS control
message, it would return an error. At that point, NFS can setup a
kvec backed msg buffer and read in the control message such as a
TLS alert. Msg iterator can advance the kvec pointer as a part of
the copy process thus we need to revert the iterator before calling
into the tls_alert_recv.

Reported-by: default avatarScott Mayhew <smayhew@redhat.com>
Fixes: 5e052dda ("SUNRPC: Recognize control messages in server-side TCP socket code")
Suggested-by: default avatarTrond Myklebust <trondmy@hammerspace.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarOlga Kornievskaia <okorniev@redhat.com>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent e5a73150

net/sunrpc/svcsock.c

+35 −8
Original line number Diff line number Diff line
@@ -257,20 +257,47 @@ svc_tcp_sock_process_cmsg(struct socket *sock, struct msghdr *msg, 
}



static int

svc_tcp_sock_recv_cmsg(struct svc_sock *svsk, struct msghdr *msg)

svc_tcp_sock_recv_cmsg(struct socket *sock, unsigned int *msg_flags)

{

	union {

		struct cmsghdr	cmsg;

		u8		buf[CMSG_SPACE(sizeof(u8))];

	} u;

	struct socket *sock = svsk->sk_sock;

	u8 alert[2];

	struct kvec alert_kvec = {

		.iov_base = alert,

		.iov_len = sizeof(alert),

	};

	struct msghdr msg = {

		.msg_flags = *msg_flags,

		.msg_control = &u,

		.msg_controllen = sizeof(u),

	};

	int ret;



	iov_iter_kvec(&msg.msg_iter, ITER_DEST, &alert_kvec, 1,

		      alert_kvec.iov_len);

	ret = sock_recvmsg(sock, &msg, MSG_DONTWAIT);

	if (ret > 0 &&

	    tls_get_record_type(sock->sk, &u.cmsg) == TLS_RECORD_TYPE_ALERT) {

		iov_iter_revert(&msg.msg_iter, ret);

		ret = svc_tcp_sock_process_cmsg(sock, &msg, &u.cmsg, -EAGAIN);

	}

	return ret;

}



static int

svc_tcp_sock_recvmsg(struct svc_sock *svsk, struct msghdr *msg)

{

	int ret;

	struct socket *sock = svsk->sk_sock;



	msg->msg_control = &u;

	msg->msg_controllen = sizeof(u);

	ret = sock_recvmsg(sock, msg, MSG_DONTWAIT);

	if (unlikely(msg->msg_controllen != sizeof(u)))

		ret = svc_tcp_sock_process_cmsg(sock, msg, &u.cmsg, ret);

	if (msg->msg_flags & MSG_CTRUNC) {

		msg->msg_flags &= ~(MSG_CTRUNC | MSG_EOR);

		if (ret == 0 || ret == -EIO)

			ret = svc_tcp_sock_recv_cmsg(sock, &msg->msg_flags);

	}

	return ret;

}
@@ -321,7 +348,7 @@ static ssize_t svc_tcp_read_msg(struct svc_rqst *rqstp, size_t buflen, 
		iov_iter_advance(&msg.msg_iter, seek);

		buflen -= seek;

	}

	len = svc_tcp_sock_recv_cmsg(svsk, &msg);

	len = svc_tcp_sock_recvmsg(svsk, &msg);

	if (len > 0)

		svc_flush_bvec(bvec, len, seek);
@@ -1018,7 +1045,7 @@ static ssize_t svc_tcp_read_marker(struct svc_sock *svsk, 
		iov.iov_base = ((char *)&svsk->sk_marker) + svsk->sk_tcplen;

		iov.iov_len  = want;

		iov_iter_kvec(&msg.msg_iter, ITER_DEST, &iov, 1, want);

		len = svc_tcp_sock_recv_cmsg(svsk, &msg);

		len = svc_tcp_sock_recvmsg(svsk, &msg);

		if (len < 0)

			return len;

		svsk->sk_tcplen += len;