commit 2821c1cc0f8cbfcc332387e83be746af6f27cb4f
author Kevin Wolf <kwolf@redhat.com> Thu Apr 30 15:30:03 2020 +0200
committer Kevin Wolf <kwolf@redhat.com> Fri May 08 13:26:35 2020 +0200
tree 8718cb3217caee3ec65fae3fc6ee98300aede534
parent 4dc20e6465eccd2466a449d3fb49539f5d9f53dd

vmdk: Fix zero cluster allocation

m_data must contain valid data even for zero clusters when no cluster
was allocated in the image file. Without this, zero writes segfault with
images that have zeroed_grain=on.

For zero writes, we don't want to allocate a cluster in the image file
even in compressed files.

Fixes: 524089bce43fd1cd3daaca979872451efa2cf7c6
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20200430133007.170335-3-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/vmdk.c

diff --git a/block/vmdk.c b/block/vmdk.c
index ecfb4a8..fcd6b38 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1572,6 +1572,12 @@
     extent->l2_cache_counts[min_index] = 1;
  found:
     l2_index = ((offset >> 9) / extent->cluster_sectors) % extent->l2_size;
+    if (m_data) {
+        m_data->l1_index = l1_index;
+        m_data->l2_index = l2_index;
+        m_data->l2_offset = l2_offset;
+        m_data->l2_cache_entry = ((uint32_t *)l2_table) + l2_index;
+    }
 
     if (extent->sesparse) {
         cluster_sector = le64_to_cpu(((uint64_t *)l2_table)[l2_index]);
@@ -1631,10 +1637,6 @@
         }
         if (m_data) {
             m_data->new_allocation = true;
-            m_data->l1_index = l1_index;
-            m_data->l2_index = l2_index;
-            m_data->l2_offset = l2_offset;
-            m_data->l2_cache_entry = ((uint32_t *)l2_table) + l2_index;
         }
     }
     *cluster_offset = cluster_sector << BDRV_SECTOR_BITS;
@@ -1990,7 +1992,7 @@
                 error_report("Could not write to allocated cluster"
                               " for streamOptimized");
                 return -EIO;
-            } else {
+            } else if (!zeroed) {
                 /* allocate */
                 ret = get_cluster_offset(bs, extent, &m_data, offset,
                                          true, &cluster_offset, 0, 0);