[PATCH v2] qcow2: Check request size in qcow2_co_pwritev_compressed_part()

[Alberto Garcia]

When issuing a compressed write request the number of bytes must be a
multiple of the cluster size or reach the end of the last cluster.

With the current code such requests are allowed and we hit an
assertion:

   $ qemu-img create -f qcow2 img.qcow2 1M
   $ qemu-io -c 'write -c 0 32k' img.qcow2

   qemu-io: block/qcow2.c:4257: qcow2_co_pwritev_compressed_task:
   Assertion `bytes == s->cluster_size || (bytes < s->cluster_size &&
              (offset + bytes == bs->total_sectors << BDRV_SECTOR_BITS))' 
failed.
   Aborted

This patch fixes a regression introduced in 0d483dce38

Signed-off-by: Alberto Garcia <be...@igalia.com>
---
 block/qcow2.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block/qcow2.c b/block/qcow2.c
index 2bb536b014..587cf51948 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -4349,6 +4349,11 @@ qcow2_co_pwritev_compressed_part(BlockDriverState *bs,
         return -EINVAL;
     }
 
+    if (offset_into_cluster(s, bytes) &&
+        (offset + bytes) != (bs->total_sectors << BDRV_SECTOR_BITS)) {
+        return -EINVAL;
+    }
+
     while (bytes && aio_task_pool_status(aio) == 0) {
         uint64_t chunk_size = MIN(bytes, s->cluster_size);
 
-- 
2.20.1