[Qemu-devel] [PATCH EMBARGOED 4/7] vmdk: check granularity field in opening

[Fam Zheng]

Granularity is used to calculate the cluster size and allocate r/w
buffer. Check the value from image before using it, so we don't abort()
for unbounded memory allocation.

Signed-off-by: Fam Zheng <address@hidden>
---
 block/vmdk.c           | 13 +++++++++++++
 tests/qemu-iotests/059 |  6 ++++++
 2 files changed, 19 insertions(+)

diff --git a/block/vmdk.c b/block/vmdk.c
index 3c6fa47..dbedff7 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -475,6 +475,13 @@ static int vmdk_open_vmdk3(BlockDriverState *bs,
     if (ret < 0) {
         return ret;
     }
+
+    if (le32_to_cpu(header.granularity) > 0x200000) {
+        /* 1GB for one cluster is unrealistic */
+        error_report("invalid granularity, image may be corrupt");
+        return -EINVAL;
+    }
+
     extent = vmdk_add_extent(bs,
                              bs->file, false,
                              le32_to_cpu(header.disk_sectors),
@@ -561,6 +568,12 @@ static int vmdk_open_vmdk4(BlockDriverState *bs,
         header = footer.header;
     }
 
+    if (le32_to_cpu(header.granularity) > 0x200000) {
+        /* 1GB for one cluster is unrealistic */
+        error_report("invalid granularity, image may be corrupt");
+        return -EINVAL;
+    }
+
     if (le32_to_cpu(header.version) >= 3) {
         char buf[64];
         snprintf(buf, sizeof(buf), "VMDK version %d",
diff --git a/tests/qemu-iotests/059 b/tests/qemu-iotests/059
index 996d85c..18807d3 100755
--- a/tests/qemu-iotests/059
+++ b/tests/qemu-iotests/059
@@ -45,6 +45,12 @@ _supported_os Linux
 
 granularity_offset=16
 
+echo "=== Testing invalid granularity ==="
+echo
+_make_test_img 64M
+poke_file "$TEST_IMG" "$granularity_offset" "\xff\xff\xff\xff\xff\xff\xff\xff"
+$QEMU_IO -c "read 0 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir
+
 # success, all done
 echo "*** done"
 rm -f $seq.full
-- 
1.8.3.4