[PATCH 3/3] block: fail on open when file size is unaligned to request_alignment

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

Prior to the commit the following command lead to crash:

  ./qemu-io --image-opts -c 'write 0 512' \
  driver=blkdebug,align=4096,image.driver=null-co,image.size=512

It failes on assertion in bdrv_aligned_pwritev:
  "end_sector <= bs->total_sectors || child->perm & BLK_PERM_RESIZE"

The problem is obvious: 512 is aligned to 4096 and becomes larger than
file size. And the core bad thing is that file size is unaligned to
request_alignment.

Let's catch such case on bdrv_open_driver and fail.

Note, that file size and request_alignment may become out of sync
later, so this commit is not full fix of the problem, but it's better
than nothing.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/block.c b/block.c
index ecd09dbbfd..4cfc6c33a2 100644
--- a/block.c
+++ b/block.c
@@ -1324,6 +1324,13 @@ static int bdrv_open_driver(BlockDriverState *bs, BlockDriver *drv,
     assert(bdrv_min_mem_align(bs) != 0);
     assert(is_power_of_2(bs->bl.request_alignment));
 
+    if (bs->bl.request_alignment > 512 &&
+        !QEMU_IS_ALIGNED(bs->total_sectors, bs->bl.request_alignment / 512))
+    {
+        error_setg(errp, "File size is unaligned to request alignment");
+        return -EINVAL;
+    }
+
     for (i = 0; i < bs->quiesce_counter; i++) {
         if (drv->bdrv_co_drain_begin) {
             drv->bdrv_co_drain_begin(bs);
-- 
2.21.0