From 60b1bd4fc5b2f5046b7b64fa5ce9c2930d482eac Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Wed, 17 Feb 2010 12:32:59 +0100
Subject: [PATCH] qemu-img: Fix segfault during rebase

This fixes a possible read beyond the end of the temporary buffers used for
comparing data in the old and the new backing file.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---
 qemu-img.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/qemu-img.c b/qemu-img.c
index 0db8d4f194..0465e4a3a8 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1224,7 +1224,7 @@ static int img_rebase(int argc, char **argv)
                 int pnum;
 
                 if (compare_sectors(buf_old + written * 512,
-                    buf_new + written * 512, n, &pnum))
+                    buf_new + written * 512, n - written, &pnum))
                 {
                     ret = bdrv_write(bs, sector + written,
                         buf_old + written * 512, pnum);
-- 
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