From 2cf9c470ebff0091e41af85f16ab906fd98cf9af Mon Sep 17 00:00:00 2001
From: Maxime Coquelin <maxime.coquelin@redhat.com>
Date: Tue, 21 Apr 2020 11:16:56 +0200
Subject: vhost: check log mmap offset and size overflow

vhost_user_set_log_base() is a message handler that is
called to handle the VHOST_USER_SET_LOG_BASE message.
Its payload contains a 64 bit size and offset. Both are
added up and used as a size when calling mmap().

There is no integer overflow check. If an integer overflow
occurs a smaller memory map would be created than
requested. Since the returned mapping is mapped as writable
and used for logging, a memory corruption could occur.

Fixes: fbc4d248b198 ("vhost: fix offset while mmaping log base address")

This issue has been assigned CVE-2020-10722

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 | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index 40c4520..02962fc 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -2060,10 +2060,10 @@ vhost_user_set_log_base(struct virtio_net **pdev, struct VhostUserMsg *msg,
 	size = msg->payload.log.mmap_size;
 	off  = msg->payload.log.mmap_offset;
 
-	/* Don't allow mmap_offset to point outside the mmap region */
-	if (off > size) {
+	/* Check for mmap size and offset overflow. */
+	if (off >= -size) {
 		RTE_LOG(ERR, VHOST_CONFIG,
-			"log offset %#"PRIx64" exceeds log size %#"PRIx64"\n",
+			"log offset %#"PRIx64" and log size %#"PRIx64" overflow\n",
 			off, size);
 		return RTE_VHOST_MSG_RESULT_ERR;
 	}
-- 
cgit v1.0

