From: ">" <duanery.duan@gmail.com>
To: mst@redhat.com, jasowang@redhat.com
Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
lidongchen@tencent.com, yongduan <yongduan@tencent.com>,
ruippan <ruippan@tencent.com>
Subject: [PATCH] vhost: make sure log_num < in_num
Date: Wed, 11 Sep 2019 17:44:24 +0800 [thread overview]
Message-ID: <1568195064-18037-1-git-send-email-yongduan@tencent.com> (raw)
From: yongduan <yongduan@tencent.com>
The code assumes log_num < in_num everywhere, and that is true as long as
in_num is incremented by descriptor iov count, and log_num by 1. However
this breaks if there's a zero sized descriptor.
As a result, if a malicious guest creates a vring desc with desc.len = 0,
it may cause the host kernel to crash by overflowing the log array. This
bug can be triggered during the VM migration.
There's no need to log when desc.len = 0, so just don't increment log_num
in this case.
Fixes: 3a4d5c94e959 ("vhost_net: a kernel-level virtio server")
Reviewed-by: Lidong Chen <lidongchen@tencent.com>
Signed-off-by: ruippan <ruippan@tencent.com>
Signed-off-by: yongduan <yongduan@tencent.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
---
drivers/vhost/vhost.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 5dc174a..36ca2cf 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2178,7 +2178,7 @@ static int get_indirect(struct vhost_virtqueue *vq,
/* If this is an input descriptor, increment that count. */
if (access == VHOST_ACCESS_WO) {
*in_num += ret;
- if (unlikely(log)) {
+ if (unlikely(log && ret)) {
log[*log_num].addr = vhost64_to_cpu(vq, desc.addr);
log[*log_num].len = vhost32_to_cpu(vq, desc.len);
++*log_num;
@@ -2319,7 +2319,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
/* If this is an input descriptor,
* increment that count. */
*in_num += ret;
- if (unlikely(log)) {
+ if (unlikely(log && ret)) {
log[*log_num].addr = vhost64_to_cpu(vq, desc.addr);
log[*log_num].len = vhost32_to_cpu(vq, desc.len);
++*log_num;
--
1.8.3.1
reply other threads:[~2019-09-11 9:45 UTC|newest]
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