block/vpc: Don't take address of fields in packed structs

Taking the address of a field in a packed struct is a bad idea, because
it might not be actually aligned enough for that pointer type (and
thus cause a crash on dereference on some host architectures). Newer
versions of clang warn about this. Avoid the bug by generating the
UUID into a local variable which is definitely safely aligned and
then copying it into place.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/block/vpc.c b/block/vpc.c
index d886465b7e29f8e732d5a05454f6eadc11e86cdb..52ab7176427db3e8e2167b78f1dfe7e3d61377d2 100644 (file)
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -979,6 +979,7 @@ static int coroutine_fn vpc_co_create(BlockdevCreateOptions *opts,
     int64_t total_size;
     int disk_type;
     int ret = -EIO;
+    QemuUUID uuid;
 
     assert(opts->driver == BLOCKDEV_DRIVER_VPC);
     vpc_opts = &opts->u.vpc;
@@ -1062,7 +1063,8 @@ static int coroutine_fn vpc_co_create(BlockdevCreateOptions *opts,
 
     footer->type = cpu_to_be32(disk_type);
 
-    qemu_uuid_generate(&footer->uuid);
+    qemu_uuid_generate(&uuid);
+    footer->uuid = uuid;
 
     footer->checksum = cpu_to_be32(vpc_checksum(buf, HEADER_SIZE));