There are only two drivers supporting vmstate: qcow2 and sheepdog.
Sheepdog is deprecated. In qcow2 these requests go through
.bdrv_co_p{read,write}v_part handlers.

So, let's do our basic check for the request on vmstate generic
handlers.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/io.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/block/io.c b/block/io.c
index 35b6c56efc..3eb6a38008 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2745,7 +2745,12 @@ bdrv_co_readv_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
 {
     BlockDriver *drv = bs->drv;
     BlockDriverState *child_bs = bdrv_primary_bs(bs);
-    int ret = -ENOTSUP;
+    int ret;
+
+    ret = bdrv_check_qiov_request(pos, qiov->size, qiov, 0, NULL);
+    if (ret < 0) {
+        return ret;
+    }
 
     if (!drv) {
         return -ENOMEDIUM;
@@ -2757,6 +2762,8 @@ bdrv_co_readv_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
         ret = drv->bdrv_load_vmstate(bs, qiov, pos);
     } else if (child_bs) {
         ret = bdrv_co_readv_vmstate(child_bs, qiov, pos);
+    } else {
+        ret = -ENOTSUP;
     }
 
     bdrv_dec_in_flight(bs);
@@ -2769,7 +2776,12 @@ bdrv_co_writev_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
 {
     BlockDriver *drv = bs->drv;
     BlockDriverState *child_bs = bdrv_primary_bs(bs);
-    int ret = -ENOTSUP;
+    int ret;
+
+    ret = bdrv_check_qiov_request(pos, qiov->size, qiov, 0, NULL);
+    if (ret < 0) {
+        return ret;
+    }
 
     if (!drv) {
         return -ENOMEDIUM;
@@ -2781,6 +2793,8 @@ bdrv_co_writev_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
         ret = drv->bdrv_save_vmstate(bs, qiov, pos);
     } else if (child_bs) {
         ret = bdrv_co_writev_vmstate(child_bs, qiov, pos);
+    } else {
+        ret = -ENOTSUP;
     }
 
     bdrv_dec_in_flight(bs);
-- 
2.29.2