[Qemu-devel] [PATCH] block: vhdx - fix reading beyond pointer during image creation

[Jeff Cody <jcody@redhat.com>]

In vhdx_create_metadata(), we allocate 40 bytes to entry_buffer for
the various metadata table entries.  However, we write out 64kB from
that buffer into the new file.  Only write out the correct 40 bytes.

Signed-off-by: Jeff Cody <jcody@redhat.com>
---
 block/vhdx.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/block/vhdx.c b/block/vhdx.c
index 796b7bd..b52ec32 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -1407,6 +1407,12 @@ exit:
     return ret;
 }
 
+#define VHDX_METADATA_ENTRY_BUFFER_SIZE \
+                                    (sizeof(VHDXFileParameters)               +\
+                                     sizeof(VHDXVirtualDiskSize)              +\
+                                     sizeof(VHDXPage83Data)                   +\
+                                     sizeof(VHDXVirtualDiskLogicalSectorSize) +\
+                                     sizeof(VHDXVirtualDiskPhysicalSectorSize))
 
 /*
  * Create the Metadata entries.
@@ -1445,11 +1451,7 @@ static int vhdx_create_new_metadata(BlockDriverState *bs,
     VHDXVirtualDiskLogicalSectorSize  *mt_log_sector_size;
     VHDXVirtualDiskPhysicalSectorSize *mt_phys_sector_size;
 
-    entry_buffer = g_malloc0(sizeof(VHDXFileParameters)               +
-                             sizeof(VHDXVirtualDiskSize)              +
-                             sizeof(VHDXPage83Data)                   +
-                             sizeof(VHDXVirtualDiskLogicalSectorSize) +
-                             sizeof(VHDXVirtualDiskPhysicalSectorSize));
+    entry_buffer = g_malloc0(VHDX_METADATA_ENTRY_BUFFER_SIZE);
 
     mt_file_params = entry_buffer;
     offset += sizeof(VHDXFileParameters);
@@ -1530,7 +1532,7 @@ static int vhdx_create_new_metadata(BlockDriverState *bs,
     }
 
     ret = bdrv_pwrite(bs, metadata_offset + (64 * KiB), entry_buffer,
-                      VHDX_HEADER_BLOCK_SIZE);
+                      VHDX_METADATA_ENTRY_BUFFER_SIZE);
     if (ret < 0) {
         goto exit;
     }
@@ -1725,7 +1727,6 @@ static int vhdx_create_new_region_table(BlockDriverState *bs,
         goto exit;
     }
 
-
 exit:
     g_free(s);
     g_free(buffer);
@@ -1876,7 +1877,6 @@ static int vhdx_create(const char *filename, QemuOpts *opts, Error **errp)
     }
 
 
-
 delete_and_exit:
     bdrv_unref(bs);
 exit:
-- 
1.9.3