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authoryongduan <yongduan@tencent.com>2019-09-11 17:44:24 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-09-16 08:23:24 +0200
commite86a7794620a589212636e0f370c98c451c7f065 (patch)
tree23fa41b99733c869e87032e3ba950a3f17239b95
parentf6b72d0920f4beec34d28e72874515ce3c3b1571 (diff)
vhost: make sure log_num < in_num
commit 060423bfdee3f8bc6e2c1bac97de24d5415e2bc4 upstream. 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") Cc: stable@vger.kernel.org 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> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/vhost/vhost.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index e995c12d8e24..fcd8bf2846fc 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2072,7 +2072,7 @@ 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;
@@ -2215,7 +2215,7 @@ 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;