qcow2: Increase maximum cluster size to 2 MB

This patch increases the maximum qcow2 cluster size to 2 MB. Starting with 128k
clusters, L2 tables span 2 GB or more of virtual disk space, causing 32 bit
truncation and wraparound of signed integers. Therefore some variables need to
use a larger data type.

While being at reviewing data types, change some integers that are used for
array indices to unsigned. In some places they were checked against some upper
limit but not for negative values. This could avoid potential segfaults with
corrupted qcow2 images.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/qemu-img.c b/qemu-img.c
index 070fe2e..204f618 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -530,7 +530,7 @@ static int is_allocated_sectors(const uint8_t *buf, int n, int *pnum)
     return v;
 }
 
-#define IO_BUF_SIZE 65536
+#define IO_BUF_SIZE (2 * 1024 * 1024)
 
 static int img_convert(int argc, char **argv)
 {