[dpdk-dev] [v17.11 PATCH v2 4/4] vhost: fix possible denial of service by leaking FDs

[Maxime Coquelin <maxime.coquelin@redhat.com>]

A malicious Vhost-user master could send in loop hand-crafted
vhost-user messages containing more file descriptors the
vhost-user slave expects. Doing so causes the application using
the vhost-user library to run out of FDs.

This issue has been assigned CVE-2019-14818

Fixes: 8f972312b8f4 ("vhost: support vhost-user")

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/vhost_user.c | 95 +++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index 781734e9e3..d4643dc350 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -81,6 +81,36 @@ static const char *vhost_message_str[VHOST_USER_MAX] = {
 	[VHOST_USER_IOTLB_MSG]  = "VHOST_USER_IOTLB_MSG",
 };
 
+static void
+close_msg_fds(struct VhostUserMsg *msg)
+{
+	int i;
+
+	for (i = 0; i < msg->fd_num; i++)
+		close(msg->fds[i]);
+}
+
+/*
+ * Ensure the expected number of FDs is received,
+ * close all FDs and return an error if this is not the case.
+ */
+static int
+validate_msg_fds(struct VhostUserMsg *msg, int expected_fds)
+{
+	if (msg->fd_num == expected_fds)
+		return 0;
+
+	RTE_LOG(ERR, VHOST_CONFIG,
+		" Expect %d FDs for request %s, received %d\n",
+		expected_fds,
+		vhost_message_str[msg->request.master],
+		msg->fd_num);
+
+	close_msg_fds(msg);
+
+	return -1;
+}
+
 static uint64_t
 get_blk_size(int fd)
 {
@@ -1458,34 +1488,58 @@ vhost_user_msg_handler(int vid, int fd)
 
 	switch (msg.request.master) {
 	case VHOST_USER_GET_FEATURES:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		msg.payload.u64 = vhost_user_get_features(dev);
 		msg.size = sizeof(msg.payload.u64);
 		send_vhost_reply(fd, &msg);
 		break;
 	case VHOST_USER_SET_FEATURES:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		vhost_user_set_features(dev, msg.payload.u64);
 		break;
 
 	case VHOST_USER_GET_PROTOCOL_FEATURES:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		vhost_user_get_protocol_features(dev, &msg);
 		send_vhost_reply(fd, &msg);
 		break;
 	case VHOST_USER_SET_PROTOCOL_FEATURES:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		vhost_user_set_protocol_features(dev, msg.payload.u64);
 		break;
 
 	case VHOST_USER_SET_OWNER:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		vhost_user_set_owner();
 		break;
 	case VHOST_USER_RESET_OWNER:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		vhost_user_reset_owner(dev);
 		break;
 
 	case VHOST_USER_SET_MEM_TABLE:
+		if (validate_msg_fds(&msg, msg.payload.memory.nregions) != 0)
+			return -1;
+
 		ret = vhost_user_set_mem_table(&dev, &msg);
 		break;
 
 	case VHOST_USER_SET_LOG_BASE:
+		if (validate_msg_fds(&msg, 1) != 0)
+			return -1;
+
 		vhost_user_set_log_base(dev, &msg);
 
 		/*
@@ -1496,61 +1550,102 @@ vhost_user_msg_handler(int vid, int fd)
 		send_vhost_reply(fd, &msg);
 		break;
 	case VHOST_USER_SET_LOG_FD:
+		if (validate_msg_fds(&msg, 1) != 0)
+			return -1;
+
 		close(msg.fds[0]);
 		RTE_LOG(INFO, VHOST_CONFIG, "not implemented.\n");
 		break;
 
 	case VHOST_USER_SET_VRING_NUM:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		vhost_user_set_vring_num(dev, &msg);
 		break;
 	case VHOST_USER_SET_VRING_ADDR:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		vhost_user_set_vring_addr(&dev, &msg);
 		break;
 	case VHOST_USER_SET_VRING_BASE:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		vhost_user_set_vring_base(dev, &msg);
 		break;
 
 	case VHOST_USER_GET_VRING_BASE:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		vhost_user_get_vring_base(dev, &msg);
 		msg.size = sizeof(msg.payload.state);
 		send_vhost_reply(fd, &msg);
 		break;
 
 	case VHOST_USER_SET_VRING_KICK:
+		if (validate_msg_fds(&msg, 1) != 0)
+			return -1;
+
 		vhost_user_set_vring_kick(&dev, &msg);
 		break;
 	case VHOST_USER_SET_VRING_CALL:
+		if (validate_msg_fds(&msg, 1) != 0)
+			return -1;
+
 		vhost_user_set_vring_call(dev, &msg);
 		break;
 
 	case VHOST_USER_SET_VRING_ERR:
+		if (validate_msg_fds(&msg, 1) != 0)
+			return -1;
+
 		if (!(msg.payload.u64 & VHOST_USER_VRING_NOFD_MASK))
 			close(msg.fds[0]);
 		RTE_LOG(INFO, VHOST_CONFIG, "not implemented\n");
 		break;
 
 	case VHOST_USER_GET_QUEUE_NUM:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
 		msg.payload.u64 = VHOST_MAX_QUEUE_PAIRS;
 		msg.size = sizeof(msg.payload.u64);
 		send_vhost_reply(fd, &msg);
 		break;
 
 	case VHOST_USER_SET_VRING_ENABLE:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		vhost_user_set_vring_enable(dev, &msg);
 		break;
 	case VHOST_USER_SEND_RARP:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		vhost_user_send_rarp(dev, &msg);
 		break;
 
 	case VHOST_USER_NET_SET_MTU:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		ret = vhost_user_net_set_mtu(dev, &msg);
 		break;
 
 	case VHOST_USER_SET_SLAVE_REQ_FD:
+		if (validate_msg_fds(&msg, 1) != 0)
+			return -1;
+
 		ret = vhost_user_set_req_fd(dev, &msg);
 		break;
 
 	case VHOST_USER_IOTLB_MSG:
+		if (validate_msg_fds(&msg, 0) != 0)
+			return -1;
+
 		ret = vhost_user_iotlb_msg(&dev, &msg);
 		break;
 
-- 
2.21.0