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[libvirt] [PATCH 02/12] storage: avoid mishandling backing store > 2GB



Detected by Coverity.  The code was doing math on shifted unsigned
char (which promotes to int), then promoting that to unsigned long
during assignment to size.  On 64-bit platforms, this risks sign
extending values of size > 2GiB.  Bug present since commit
489fd3 (v0.6.0).

I'm not sure if a specially-crafted bogus qcow2 image could
exploit this, although it's probably not possible, since we
were already checking for the computed results being within
range of our fixed-size buffer.

* src/util/storage_file.c (qcowXGetBackingStore): Avoid sign
extension.
---
 src/util/storage_file.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/src/util/storage_file.c b/src/util/storage_file.c
index 6b3b756..6749599 100644
--- a/src/util/storage_file.c
+++ b/src/util/storage_file.c
@@ -27,6 +27,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <stdint.h>
 #ifdef __linux__
 # if HAVE_LINUX_MAGIC_H
 #  include <linux/magic.h>
@@ -274,7 +275,7 @@ qcowXGetBackingStore(char **res,
                      bool isQCow2)
 {
     unsigned long long offset;
-    unsigned long size;
+    uint32_t size;

     *res = NULL;
     if (format)
-- 
1.7.4.4


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