[libvirt] [PATCH 09/30] storagefile: Push extension_end calc to qcow2GetBackingStoreFormat
This is a step towards making this qcow2GetBackingStoreFormat into
a generic qcow2 extensions parser
Signed-off-by: Cole Robinson <crobinso(a)redhat.com>
---
src/util/virstoragefile.c | 66 +++++++++++++++++++++------------------
1 file changed, 35 insertions(+), 31 deletions(-)
diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
index 4a3c9df7a2..b8f7faf580 100644
--- a/src/util/virstoragefile.c
+++ b/src/util/virstoragefile.c
@@ -429,11 +429,11 @@ cowGetBackingStore(char **res,
static int
qcow2GetBackingStoreFormat(int *format,
const char *buf,
- size_t buf_size,
- size_t extension_end)
+ size_t buf_size)
{
size_t offset;
size_t extension_start;
+ size_t extension_end;
int version = virReadBufInt32BE(buf + QCOWX_HDR_VERSION);
if (version < 2) {
@@ -447,6 +447,37 @@ qcow2GetBackingStoreFormat(int *format,
else
extension_start = virReadBufInt32BE(buf + QCOW2v3_HDR_SIZE);
+ /*
+ * Traditionally QCow2 files had a layout of
+ *
+ * [header]
+ * [backingStoreName]
+ *
+ * Although the backingStoreName typically followed
+ * the header immediately, this was not required by
+ * the format. By specifying a higher byte offset for
+ * the backing file offset in the header, it was
+ * possible to leave space between the header and
+ * start of backingStore.
+ *
+ * This hack is now used to store extensions to the
+ * qcow2 format:
+ *
+ * [header]
+ * [extensions]
+ * [backingStoreName]
+ *
+ * Thus the file region to search for extensions is
+ * between the end of the header (QCOW2_HDR_TOTAL_SIZE)
+ * and the start of the backingStoreName (offset)
+ *
+ * for qcow2 v3 images, the length of the header
+ * is stored at QCOW2v3_HDR_SIZE
+ */
+ extension_end = virReadBufInt64BE(buf + QCOWX_HDR_BACKING_FILE_OFFSET);
+ if (extension_end > buf_size)
+ return -1;
+
/*
* The extensions take format of
*
@@ -506,6 +537,7 @@ qcowXGetBackingStore(char **res,
if (buf_size < QCOWX_HDR_BACKING_FILE_OFFSET+8+4)
return BACKING_STORE_INVALID;
+
offset = virReadBufInt64BE(buf + QCOWX_HDR_BACKING_FILE_OFFSET);
if (offset > buf_size)
return BACKING_STORE_INVALID;
@@ -529,35 +561,7 @@ qcowXGetBackingStore(char **res,
memcpy(*res, buf + offset, size);
(*res)[size] = '\0';
- /*
- * Traditionally QCow2 files had a layout of
- *
- * [header]
- * [backingStoreName]
- *
- * Although the backingStoreName typically followed
- * the header immediately, this was not required by
- * the format. By specifying a higher byte offset for
- * the backing file offset in the header, it was
- * possible to leave space between the header and
- * start of backingStore.
- *
- * This hack is now used to store extensions to the
- * qcow2 format:
- *
- * [header]
- * [extensions]
- * [backingStoreName]
- *
- * Thus the file region to search for extensions is
- * between the end of the header (QCOW2_HDR_TOTAL_SIZE)
- * and the start of the backingStoreName (offset)
- *
- * for qcow2 v3 images, the length of the header
- * is stored at QCOW2v3_HDR_SIZE
- */
-
- if (qcow2GetBackingStoreFormat(format, buf, buf_size, offset) < 0)
+ if (qcow2GetBackingStoreFormat(format, buf, buf_size) < 0)
return BACKING_STORE_INVALID;
return BACKING_STORE_OK;
--
2.23.0