Convert jffs2 acl to struct_size

Need to tell the compiler that the acl entries follow the acl header.
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

fs/jffs2/acl.c

@@ -133,7 +133,8 @@ static void *jffs2_acl_to_medium(const struct posix_acl *acl, size_t *size)
 	size_t i;
 
 	*size = jffs2_acl_size(acl->a_count);
-	header = kmalloc(sizeof(*header) + acl->a_count * sizeof(*entry), GFP_KERNEL);
+	header = kmalloc(struct_size(header, a_entries, acl->a_count),
+			GFP_KERNEL);
 	if (!header)
 		return ERR_PTR(-ENOMEM);
 	header->a_version = cpu_to_je32(JFFS2_ACL_VERSION);

fs/jffs2/acl.h

@@ -22,6 +22,7 @@ struct jffs2_acl_entry_short {
 
 struct jffs2_acl_header {
 	jint32_t	a_version;
+	struct jffs2_acl_entry	a_entries[];
 };
 
 #ifdef CONFIG_JFFS2_FS_POSIX_ACL