lsm: align based on pointer length in lsm_fill_user_ctx()

Using the size of a void pointer is much cleaner than
BITS_PER_LONG / 8.
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/security.c

@@ -792,7 +792,7 @@ int lsm_fill_user_ctx(struct lsm_ctx __user *uctx, size_t *uctx_len,
 	size_t nctx_len;
 	int rc = 0;
 
-	nctx_len = ALIGN(struct_size(nctx, ctx, val_len), BITS_PER_LONG / 8);
+	nctx_len = ALIGN(struct_size(nctx, ctx, val_len), sizeof(void *));
 	if (nctx_len > *uctx_len) {
 		rc = -E2BIG;
 		goto out;