Convert vhost to struct_size

Signed-off-by: Matthew Wilcox <[e-mail]>
Signed-off-by: Kees Cook <[e-mail]>

drivers/vhost/vhost.c

···
 		return -EOPNOTSUPP;
 	if (mem.nregions > max_mem_regions)
 		return -E2BIG;
-	newmem = kvzalloc(size + mem.nregions * sizeof(*m->regions), GFP_KERNEL);
+	newmem = kvzalloc(struct_size(newmem, regions, mem.nregions),
+			GFP_KERNEL);
 	if (!newmem)
 		return -ENOMEM;