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 AE790C4332F for ; Fri, 21 Oct 2022 02:11:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229757AbiJUCLx (ORCPT ); Thu, 20 Oct 2022 22:11:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38166 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229489AbiJUCLw (ORCPT ); Thu, 20 Oct 2022 22:11:52 -0400 Received: from smtpout.efficios.com (smtpout.efficios.com [IPv6:2607:5300:203:5aae::31e5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AC84E1EEA2D; Thu, 20 Oct 2022 19:11:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1666318308; bh=YYLNRpLFjpOx3zPbx2dWD9ifcWMbbBXNZdhWZRlErMs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=FCRNNf/SxQz2jg1jx9wfUn4kq/dv5zt3ogNg+jvjR7fS5A7T6AVrzviTCEDYrY5/b SJgfcXBIEmQ5L11Ay9HdYW93i85isJ+0SIeZdw02lZnI4dv3iUu30oGo21olvHTfcL J6IOMo7TSic7m5KnQ1U65cMtPwNtzwgqCozc3DPKYPIwsLSWRF7Mdi3NlFHxALjyp4 kepwEM+z7d+b34Bvu1x0N0AgkijDlgmmPPPF9M7NDjQd0y4fGclhlA59mXCMxmAArT yaIAsNIQvGz5JiEVp251at8ZUA1GTHhI5inajwK24QP6h6qdFcTUo5geWRYKebeXBp jtMmYS/jv2s/g== Received: from [10.1.0.216] (192-222-188-69.qc.cable.ebox.net [192.222.188.69]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4Mtnyr1BYXzVCZ; Thu, 20 Oct 2022 22:11:48 -0400 (EDT) Message-ID: <7652446f-424f-35c1-6ebb-c8ffd8c99b1a@efficios.com> Date: Thu, 20 Oct 2022 22:11:42 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.0 Subject: Re: [RFC PATCH] rseq: Use pr_warn_once() when deprecated/unknown ABI flags are encountered Content-Language: en-US To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , "Paul E . McKenney" , Boqun Feng , "H . Peter Anvin" , Paul Turner , linux-api@vger.kernel.org, Peter Oskolkov , Mark Rutland References: <20220929141227.205343-1-mathieu.desnoyers@efficios.com> From: Mathieu Desnoyers In-Reply-To: <20220929141227.205343-1-mathieu.desnoyers@efficios.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On 2022-09-29 10:12, Mathieu Desnoyers wrote: > These commits use WARN_ON_ONCE() and kill the offending processes when > deprecated and unknown flags are encountered: > > commit c17a6ff93213 ("rseq: Kill process when unknown flags are encountered in ABI structures") > commit 0190e4198e47 ("rseq: Deprecate RSEQ_CS_FLAG_NO_RESTART_ON_* flags") > > The WARN_ON_ONCE() triggered by userspace input prevents use of > Syzkaller to fuzz the rseq system call. > > Replace this WARN_ON_ONCE() by pr_warn_once() messages which contain > actually useful information. Hi Peter, Should I resubmit this or can you simply pick up the Acked-by from Paul McKenney and Mark Rutland and route this through the tip tree ? Thanks, Mathieu > > Reported-by: Mark Rutland > Signed-off-by: Mathieu Desnoyers > --- > kernel/rseq.c | 19 +++++++++++++++++-- > 1 file changed, 17 insertions(+), 2 deletions(-) > > diff --git a/kernel/rseq.c b/kernel/rseq.c > index bda8175f8f99..d38ab944105d 100644 > --- a/kernel/rseq.c > +++ b/kernel/rseq.c > @@ -171,12 +171,27 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) > return 0; > } > > +static bool rseq_warn_flags(const char *str, u32 flags) > +{ > + u32 test_flags; > + > + if (!flags) > + return false; > + test_flags = flags & RSEQ_CS_NO_RESTART_FLAGS; > + if (test_flags) > + pr_warn_once("Deprecated flags (%u) in %s ABI structure", test_flags, str); > + test_flags = flags & ~RSEQ_CS_NO_RESTART_FLAGS; > + if (test_flags) > + pr_warn_once("Unknown flags (%u) in %s ABI structure", test_flags, str); > + return true; > +} > + > static int rseq_need_restart(struct task_struct *t, u32 cs_flags) > { > u32 flags, event_mask; > int ret; > > - if (WARN_ON_ONCE(cs_flags & RSEQ_CS_NO_RESTART_FLAGS) || cs_flags) > + if (rseq_warn_flags("rseq_cs", cs_flags)) > return -EINVAL; > > /* Get thread flags. */ > @@ -184,7 +199,7 @@ static int rseq_need_restart(struct task_struct *t, u32 cs_flags) > if (ret) > return ret; > > - if (WARN_ON_ONCE(flags & RSEQ_CS_NO_RESTART_FLAGS) || flags) > + if (rseq_warn_flags("rseq", flags)) > return -EINVAL; > > /* -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com