The checks in vu_blk_sect_range_ok() assume VIRTIO_BLK_SECTOR_SIZE is
equal to BDRV_SECTOR_SIZE. This is true, but let's add a
QEMU_BUILD_BUG_ON() to make it explicit.

We might as well check that the request buffer size is a multiple of
VIRTIO_BLK_SECTOR_SIZE while we're at it.

Suggested-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/export/vhost-user-blk-server.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/block/export/vhost-user-blk-server.c b/block/export/vhost-user-blk-server.c
index fa06996d37..1862563336 100644
--- a/block/export/vhost-user-blk-server.c
+++ b/block/export/vhost-user-blk-server.c
@@ -70,9 +70,16 @@ static void vu_blk_req_complete(VuBlkReq *req)
 static bool vu_blk_sect_range_ok(VuBlkExport *vexp, uint64_t sector,
                                  size_t size)
 {
-    uint64_t nb_sectors = size >> BDRV_SECTOR_BITS;
+    uint64_t nb_sectors;
     uint64_t total_sectors;
 
+    if (size % VIRTIO_BLK_SECTOR_SIZE) {
+        return false;
+    }
+
+    nb_sectors = size >> VIRTIO_BLK_SECTOR_BITS;
+
+    QEMU_BUILD_BUG_ON(BDRV_SECTOR_SIZE != VIRTIO_BLK_SECTOR_SIZE);
     if (nb_sectors > BDRV_REQUEST_MAX_SECTORS) {
         return false;
     }
-- 
2.30.2

On 3/31/21 9:27 AM, Stefan Hajnoczi wrote:
> The checks in vu_blk_sect_range_ok() assume VIRTIO_BLK_SECTOR_SIZE is
> equal to BDRV_SECTOR_SIZE. This is true, but let's add a
> QEMU_BUILD_BUG_ON() to make it explicit.
> 
> We might as well check that the request buffer size is a multiple of
> VIRTIO_BLK_SECTOR_SIZE while we're at it.
> 
> Suggested-by: Max Reitz <mreitz@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  block/export/vhost-user-blk-server.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org