qcow2: Assert against snapshot name/ID overflow

qcow2_write_snapshots relies on the length of every snapshot ID and name
fitting into an unsigned 16 bit integer. This is currently ensured by
QEMU through generally only allowing 128 byte IDs and 256 byte names.
However, if this should change in the future, the length written to the
image file should not be silently truncated (though the name itself
would be written completely).

Since this is currently not an issue but might require attention due to
internal QEMU changes in the future, an assert ensuring sanity is enough
for now.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index f6f3e6423d5cb8b9a8408dea1b85daeed8cb05ba..812dab2aa5d32b5e6caedae28915b2de6549a4e8 100644 (file)
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -221,6 +221,7 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
 
         id_str_size = strlen(sn->id_str);
         name_size = strlen(sn->name);
+        assert(id_str_size <= UINT16_MAX && name_size <= UINT16_MAX);
         h.id_str_size = cpu_to_be16(id_str_size);
         h.name_size = cpu_to_be16(name_size);
         offset = align_offset(offset, 8);