From 8e9652b0b616a3704b5cb5a3dccb2c239e16ab9c Mon Sep 17 00:00:00 2001
From: Maxime Coquelin <maxime.coquelin@redhat.com>
Date: Tue, 21 Apr 2020 18:17:43 +0200
Subject: vhost: fix vring index check

vhost_user_check_and_alloc_queue_pair() is used to extract
a vring index from a payload. This function validates the
index and is called early on in when performing message
handling. Most message handlers depend on it correctly
validating the vring index.

Depending on the message type the vring index is in
different parts of the payload. The function contains a
switch/case for each type and copies the index. This is
stored in a uint16. This index is then validated. Depending
on the message, the source index is an unsigned int. If
integer truncation occurs (uint->uint16) the top 16 bits
of the index are never validated.

When they are used later on  (e.g. in
vhost_user_set_vring_num() or vhost_user_set_vring_addr())
it can lead to out of bound indexing. The out of bound
indexed data gets written to, and hence this can cause
memory corruption.

This patch fixes this vulnerability by declaring vring
index as an unsigned int in
vhost_user_check_and_alloc_queue_pair().

Fixes: 160cbc815b41 ("vhost: remove a hack on queue allocation")

This issue has been assigned CVE-2020-10723

Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Xiaolong Ye <xiaolong.ye@intel.com>
Reviewed-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
---
 lib/librte_vhost/vhost_user.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index 02962fc..d196142 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -2508,7 +2508,7 @@ static int
 vhost_user_check_and_alloc_queue_pair(struct virtio_net *dev,
 			struct VhostUserMsg *msg)
 {
-	uint16_t vring_idx;
+	uint32_t vring_idx;
 
 	switch (msg->request.master) {
 	case VHOST_USER_SET_VRING_KICK:
-- 
cgit v1.0

