From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 459C1C77B75 for ; Tue, 23 May 2023 13:08:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235598AbjEWNIH (ORCPT ); Tue, 23 May 2023 09:08:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45136 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230283AbjEWNIE (ORCPT ); Tue, 23 May 2023 09:08:04 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3A6F6126 for ; Tue, 23 May 2023 06:08:02 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id AC5CE63235 for ; Tue, 23 May 2023 13:08:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 63831C433D2; Tue, 23 May 2023 13:07:58 +0000 (UTC) Date: Tue, 23 May 2023 14:07:55 +0100 From: Catalin Marinas To: David Hildenbrand Cc: Alexey Izbyshev , Florent Revest , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, anshuman.khandual@arm.com, joey.gouly@arm.com, mhocko@suse.com, keescook@chromium.org, peterx@redhat.com, broonie@kernel.org, szabolcs.nagy@arm.com, kpsingh@kernel.org, gthelen@google.com, toiwoton@gmail.com Subject: Re: [PATCH v2 3/5] mm: Make PR_MDWE_REFUSE_EXEC_GAIN an unsigned long Message-ID: References: <20230517150321.2890206-1-revest@chromium.org> <20230517150321.2890206-4-revest@chromium.org> <884d131bbc28ebfa0b729176e6415269@ispras.ru> <3c2e210b75bd56909322e8a3e5086d91@ispras.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 23, 2023 at 11:12:37AM +0200, David Hildenbrand wrote: > Also, how is passing "0"s to e.g., PR_GET_THP_DISABLE reliable? We need arg2 > -> arg5 to be 0. But wouldn't the following also just pass a 0 "int" ? > > prctl(PR_GET_THP_DISABLE, 0, 0, 0, 0) > > I'm easily confused by such (va_args) things, so sorry for the dummy > questions. Isn't the prctl() prototype in the user headers defined with the first argument as int while the rest as unsigned long? At least from the man page: int prctl(int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5); So there are no va_args tricks (which confuse me as well). Any int passed to arg[2-5] would be converted by the compiler to an unsigned long before being passed to the kernel. So I think the change in this patch is harmless as the conversion is happening anyway. (well, unless I completely missed what the problem is) -- Catalin