qcow2: Fix alignment checks in encrypted images

I/O requests to encrypted media should be aligned to the sector size
used by the underlying encryption method, not to BDRV_SECTOR_SIZE.
Fortunately this doesn't break anything at the moment because
both existing QCRYPTO_BLOCK_*_SECTOR_SIZE have the same value as
BDRV_SECTOR_SIZE.

The checks in qcow2_co_preadv_encrypted() are also unnecessary because
they are repeated immediately afterwards in qcow2_co_encdec().

Signed-off-by: Alberto Garcia <berto@igalia.com>
Message-Id: <20200213171646.15876-1-berto@igalia.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/qcow2-threads.c

@@ -246,12 +246,15 @@ qcow2_co_encdec(BlockDriverState *bs, uint64_t host_offset,
         .len = len,
         .func = func,
     };
+    uint64_t sector_size;
 
-    assert(QEMU_IS_ALIGNED(guest_offset, BDRV_SECTOR_SIZE));
-    assert(QEMU_IS_ALIGNED(host_offset, BDRV_SECTOR_SIZE));
-    assert(QEMU_IS_ALIGNED(len, BDRV_SECTOR_SIZE));
     assert(s->crypto);
 
+    sector_size = qcrypto_block_get_sector_size(s->crypto);
+    assert(QEMU_IS_ALIGNED(guest_offset, sector_size));
+    assert(QEMU_IS_ALIGNED(host_offset, sector_size));
+    assert(QEMU_IS_ALIGNED(len, sector_size));
+
     return len == 0 ? 0 : qcow2_co_process(bs, qcow2_encdec_pool_func, &arg);
 }
 
@@ -270,7 +273,8 @@ qcow2_co_encdec(BlockDriverState *bs, uint64_t host_offset,
  *        will be written to the underlying storage device at
  *        @host_offset
  *
- * @len - length of the buffer (must be a BDRV_SECTOR_SIZE multiple)
+ * @len - length of the buffer (must be a multiple of the encryption
+ *        sector size)
  *
  * Depending on the encryption method, @host_offset and/or @guest_offset
  * may be used for generating the initialization vector for

block/qcow2.c

@@ -2068,8 +2068,6 @@ qcow2_co_preadv_encrypted(BlockDriverState *bs,
         goto fail;
     }
 
-    assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
-    assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
     if (qcow2_co_decrypt(bs,
                          file_cluster_offset + offset_into_cluster(s, offset),
                          offset, buf, bytes) < 0)