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 X-Spam-Level: X-Spam-Status: No, score=-18.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 76F07C4338F for ; Fri, 30 Jul 2021 12:22:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4FA5260230 for ; Fri, 30 Jul 2021 12:22:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238739AbhG3MWs (ORCPT ); Fri, 30 Jul 2021 08:22:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:50810 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230325AbhG3MWq (ORCPT ); Fri, 30 Jul 2021 08:22:46 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 73F3360F0F; Fri, 30 Jul 2021 12:22:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627647761; bh=6rPDKOhXYLbds6nrD5HJGHt+dOnovarXwROp9/CyKZQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WlMh3a4XCuGOTkoRFslKFOC5+jQetKCuY/TGSoGMd8duetvdFMbYrlk/juRI5DszS o/21RNLixzIm0twxsanZdlfA9ud7qzIXIoCTJy+w35c9BZN88mAzALUXUYZ+0BC6SE bgQQk3N64Kl+qQs+4ne9MHMNxzLRLU77mcDeA+Nk8307mNHaa4l6Rje9ium3weZmQB aRt65/xJkTlgY899amR/yd+aDgBxS8/hVeVb5eQiCGPasZEEsgfLWvyOYFYQpUY7rb ZaEVIQOLmgwZOHs93DOhsRVASXlP9jOud2GALq738PRXWobe6a4Gzy9Zu0iaobh8oo F89/OkH6DsLBg== Date: Fri, 30 Jul 2021 13:22:37 +0100 From: Will Deacon To: Yuchen Wei , mark.rutland@arm.com Cc: catalin.marinas@arm.com, vincenzo.frascino@arm.com, keescook@chromium.org, pcc@google.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64: audit: fix return value high 32bit truncation problem Message-ID: <20210730122236.GE23589@willie-the-truck> References: <20210722060707.531-1-weiyuchen3@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210722060707.531-1-weiyuchen3@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 22, 2021 at 02:07:07PM +0800, Yuchen Wei wrote: > From: weiyuchen > > Add error code judgment in invoke_syscall() to prevent kernel > components such as audit and tracepoint from obtaining incorrect > return values. For example: > > type=SYSCALL msg=audit(342.780:69): arch=40000028 syscall=235 > success=yes exit=4294967235 > > The syscall return value is -61, but due to the following process in > invoke_syscall(): > > if (is_compat_task()) > ret = lower_32_bits(ret); > regs->regs[0] = ret; > > The return value audit or tracepoint get from regs[0] is 4294967235, > which is an incorrect return value. > > Signed-off-by: weiyuchen > --- > arch/arm64/kernel/syscall.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c > index 263d6c1a525f..f9f042d9a088 100644 > --- a/arch/arm64/kernel/syscall.c > +++ b/arch/arm64/kernel/syscall.c > @@ -54,7 +54,7 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno, > ret = do_ni_syscall(regs, scno); > } > > - if (is_compat_task()) > + if (is_compat_task() && !IS_ERR_VALUE(ret)) > ret = lower_32_bits(ret); Hmm, I'm worried this might break other users who don't expect to see non-zero bits for the upper 32-bits of a compat task. Mark -- I remember you looking into this relatively recently. Where did you get to with it? Will