Commit 060423bf authored by yongduan's avatar yongduan Committed by Michael S. Tsirkin

vhost: make sure log_num < in_num

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: 3a4d5c94 ("vhost_net: a kernel-level virtio server")
Cc: stable@vger.kernel.org
Reviewed-by: default avatarLidong Chen <lidongchen@tencent.com>
Signed-off-by: default avatarruippan <ruippan@tencent.com>
Signed-off-by: default avataryongduan <yongduan@tencent.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: default avatarTyler Hicks <tyhicks@canonical.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent a89db445
......@@ -2180,7 +2180,7 @@ 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;
......@@ -2321,7 +2321,7 @@ 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;
......
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