[Qemu-devel] [PATCH] block/vdi: Fix image opening and creation for odd disk sizes

[Stefan Weil <weil@mail.berlios.de>]

The fix is based on a patch from Kevin Wolf. Here his comment:

"The number of blocks needs to be rounded up to cover all of the virtual hard
disk. Without this fix, we can't even open our own images if their size is not
a multiple of the block size."

While Kevin's patch addressed vdi_create, my modification also fixes
vdi_open which now accepts images with odd disk sizes.

v3:
Don't allow reading of disk images with too large disk sizes.
Neither VBoxManage nor old versions of qemu-img read such images.
This change requires rounding of odd disk sizes before we do the checks.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: François Revol <revol@free.fr>
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
---
 block/vdi.c |   23 ++++++++++++++++-------
 1 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/block/vdi.c b/block/vdi.c
index 1ce18d5..b53a3c1 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -393,6 +393,15 @@ static int vdi_open(BlockDriverState *bs, int flags)
     vdi_header_print(&header);
 #endif
 
+    if (header.disk_size % SECTOR_SIZE != 0) {
+        /* 'VBoxManage convertfromraw' can create images with odd disk sizes.
+           We accept them but round the disk size to the next multiple of
+           SECTOR_SIZE. */
+        logout("odd disk size %" PRIu64 " B, round up\n", header.disk_size);
+        header.disk_size += SECTOR_SIZE - 1;
+        header.disk_size &= ~(SECTOR_SIZE - 1);
+    }
+
     if (header.version != VDI_VERSION_1_1) {
         logout("unsupported version %u.%u\n",
                header.version >> 16, header.version & 0xffff);
@@ -405,18 +414,15 @@ static int vdi_open(BlockDriverState *bs, int flags)
         /* We only support data blocks which start on a sector boundary. */
         logout("unsupported data offset 0x%x B\n", header.offset_data);
         goto fail;
-    } else if (header.disk_size % SECTOR_SIZE != 0) {
-        logout("unsupported disk size %" PRIu64 " B\n", header.disk_size);
-        goto fail;
     } else if (header.sector_size != SECTOR_SIZE) {
         logout("unsupported sector size %u B\n", header.sector_size);
         goto fail;
     } else if (header.block_size != 1 * MiB) {
         logout("unsupported block size %u B\n", header.block_size);
         goto fail;
-    } else if ((header.disk_size + header.block_size - 1) / header.block_size !=
-               (uint64_t)header.blocks_in_image) {
-        logout("unexpected block number %u B\n", header.blocks_in_image);
+    } else if (header.disk_size >
+               (uint64_t)header.blocks_in_image * header.block_size) {
+        logout("unsupported disk size %" PRIu64 " B\n", header.disk_size);
         goto fail;
     } else if (!uuid_is_null(header.uuid_link)) {
         logout("link uuid != 0, unsupported\n");
@@ -829,7 +835,10 @@ static int vdi_create(const char *filename, QEMUOptionParameter *options)
         return -errno;
     }
 
-    blocks = bytes / block_size;
+    /* We need enough blocks to store the given disk size,
+       so always round up. */
+    blocks = (bytes + block_size - 1) / block_size;
+
     bmap_size = blocks * sizeof(uint32_t);
     bmap_size = ((bmap_size + SECTOR_SIZE - 1) & ~(SECTOR_SIZE -1));
 
-- 
1.7.1