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=-10.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,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 C7CA3C4338F for ; Wed, 28 Jul 2021 17:58:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ACE376103C for ; Wed, 28 Jul 2021 17:58:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230054AbhG1R6H (ORCPT ); Wed, 28 Jul 2021 13:58:07 -0400 Received: from mga09.intel.com ([134.134.136.24]:40264 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229542AbhG1R6F (ORCPT ); Wed, 28 Jul 2021 13:58:05 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10059"; a="212710547" X-IronPort-AV: E=Sophos;i="5.84,276,1620716400"; d="scan'208";a="212710547" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Jul 2021 10:58:02 -0700 X-IronPort-AV: E=Sophos;i="5.84,276,1620716400"; d="scan'208";a="517729036" Received: from sobsiex-desk2.amr.corp.intel.com (HELO [10.212.198.197]) ([10.212.198.197]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Jul 2021 10:58:01 -0700 Subject: Re: [PATCH] x86/fault: Fix wrong signal when vsyscall fails with pkey To: Jiashuo Liang , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" Cc: linux-kernel@vger.kernel.org References: <20210728114413.287611-1-liangjs@pku.edu.cn> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; keydata= xsFNBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABzShEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gPGRhdmVAc3I3MS5uZXQ+wsF7BBMBAgAlAhsDBgsJCAcDAgYVCAIJ CgsEFgIDAQIeAQIXgAUCTo3k0QIZAQAKCRBoNZUwcMmSsMO2D/421Xg8pimb9mPzM5N7khT0 2MCnaGssU1T59YPE25kYdx2HntwdO0JA27Wn9xx5zYijOe6B21ufrvsyv42auCO85+oFJWfE K2R/IpLle09GDx5tcEmMAHX6KSxpHmGuJmUPibHVbfep2aCh9lKaDqQR07gXXWK5/yU1Dx0r VVFRaHTasp9fZ9AmY4K9/BSA3VkQ8v3OrxNty3OdsrmTTzO91YszpdbjjEFZK53zXy6tUD2d e1i0kBBS6NLAAsqEtneplz88T/v7MpLmpY30N9gQU3QyRC50jJ7LU9RazMjUQY1WohVsR56d ORqFxS8ChhyJs7BI34vQusYHDTp6PnZHUppb9WIzjeWlC7Jc8lSBDlEWodmqQQgp5+6AfhTD kDv1a+W5+ncq+Uo63WHRiCPuyt4di4/0zo28RVcjtzlGBZtmz2EIC3vUfmoZbO/Gn6EKbYAn rzz3iU/JWV8DwQ+sZSGu0HmvYMt6t5SmqWQo/hyHtA7uF5Wxtu1lCgolSQw4t49ZuOyOnQi5 f8R3nE7lpVCSF1TT+h8kMvFPv3VG7KunyjHr3sEptYxQs4VRxqeirSuyBv1TyxT+LdTm6j4a mulOWf+YtFRAgIYyyN5YOepDEBv4LUM8Tz98lZiNMlFyRMNrsLV6Pv6SxhrMxbT6TNVS5D+6 UorTLotDZKp5+M7BTQRUY85qARAAsgMW71BIXRgxjYNCYQ3Xs8k3TfAvQRbHccky50h99TUY sqdULbsb3KhmY29raw1bgmyM0a4DGS1YKN7qazCDsdQlxIJp9t2YYdBKXVRzPCCsfWe1dK/q 66UVhRPP8EGZ4CmFYuPTxqGY+dGRInxCeap/xzbKdvmPm01Iw3YFjAE4PQ4hTMr/H76KoDbD cq62U50oKC83ca/PRRh2QqEqACvIH4BR7jueAZSPEDnzwxvVgzyeuhwqHY05QRK/wsKuhq7s UuYtmN92Fasbxbw2tbVLZfoidklikvZAmotg0dwcFTjSRGEg0Gr3p/xBzJWNavFZZ95Rj7Et db0lCt0HDSY5q4GMR+SrFbH+jzUY/ZqfGdZCBqo0cdPPp58krVgtIGR+ja2Mkva6ah94/oQN lnCOw3udS+Eb/aRcM6detZr7XOngvxsWolBrhwTQFT9D2NH6ryAuvKd6yyAFt3/e7r+HHtkU kOy27D7IpjngqP+b4EumELI/NxPgIqT69PQmo9IZaI/oRaKorYnDaZrMXViqDrFdD37XELwQ gmLoSm2VfbOYY7fap/AhPOgOYOSqg3/Nxcapv71yoBzRRxOc4FxmZ65mn+q3rEM27yRztBW9 AnCKIc66T2i92HqXCw6AgoBJRjBkI3QnEkPgohQkZdAb8o9WGVKpfmZKbYBo4pEAEQEAAcLB XwQYAQIACQUCVGPOagIbDAAKCRBoNZUwcMmSsJeCEACCh7P/aaOLKWQxcnw47p4phIVR6pVL e4IEdR7Jf7ZL00s3vKSNT+nRqdl1ugJx9Ymsp8kXKMk9GSfmZpuMQB9c6io1qZc6nW/3TtvK pNGz7KPPtaDzvKA4S5tfrWPnDr7n15AU5vsIZvgMjU42gkbemkjJwP0B1RkifIK60yQqAAlT YZ14P0dIPdIPIlfEPiAWcg5BtLQU4Wg3cNQdpWrCJ1E3m/RIlXy/2Y3YOVVohfSy+4kvvYU3 lXUdPb04UPw4VWwjcVZPg7cgR7Izion61bGHqVqURgSALt2yvHl7cr68NYoFkzbNsGsye9ft M9ozM23JSgMkRylPSXTeh5JIK9pz2+etco3AfLCKtaRVysjvpysukmWMTrx8QnI5Nn5MOlJj 1Ov4/50JY9pXzgIDVSrgy6LYSMc4vKZ3QfCY7ipLRORyalFDF3j5AGCMRENJjHPD6O7bl3Xo 4DzMID+8eucbXxKiNEbs21IqBZbbKdY1GkcEGTE7AnkA3Y6YB7I/j9mQ3hCgm5muJuhM/2Fr OPsw5tV/LmQ5GXH0JQ/TZXWygyRFyyI2FqNTx4WHqUn3yFj8rwTAU1tluRUYyeLy0ayUlKBH ybj0N71vWO936MqP6haFERzuPAIpxj2ezwu0xb1GjTk4ynna6h5GjnKgdfOWoRtoWndMZxbA z5cecg== Message-ID: <87c4acb3-c3a9-c682-138b-0f85246e9cb8@intel.com> Date: Wed, 28 Jul 2021 10:57:58 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210728114413.287611-1-liangjs@pku.edu.cn> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/28/21 4:44 AM, Jiashuo Liang wrote: > The function __bad_area_nosemaphore calls kernelmode_fixup_or_oops with > parameter "signal" being "pkey", which will send a signal numbered "pkey". Yikes. > When emulating vsyscall, the kernel may fail to access user-given memory > pages that are protected by pkey. In such a case, the kernel should send a > SIGSEGV signal with si_code=SEGV_PKUERR and si_pkey=pkey. This could use a bit more context. First of all this is for user address space faults in the do_user_addr_fault() path. Second, the buggy code is under a !user_mode() check, so this must be a kernel fault in the user address space. Third, the only notice this problem when the page fault handler ends up delivering a signal as a result of the fault. Most cases will simply return an error code to the faulting kernel code which will see -EFAULT come back from copy_to/from_user() and friends. The *only* condition in which we generate that signal from the fault handler is when current->thread.sig_on_uaccess_err=1, and the only place that gets used is in emulate_vsyscall(). This makes me want to add some code that tickles vsyscall emulation in the pkey selftests, but I think I'll resist the urge for now. :) Is that all correct? > So a new parameter "pkey" is added to kernelmode_fixup_or_oops to fix it. Yeah, I think that's the right fix. You also need this: Fixes: 5042d40a264c ("x86/fault: Bypass no_context() for implicit kernel faults from usermode") I believe that's where this issue originated. How did you find this, by the way? > arch/x86/mm/fault.c | 23 +++++++++++++++-------- > 1 file changed, 15 insertions(+), 8 deletions(-) > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > index b2eefdefc108..883294282e1e 100644 > --- a/arch/x86/mm/fault.c > +++ b/arch/x86/mm/fault.c > @@ -710,7 +710,8 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code, > > static noinline void > kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code, > - unsigned long address, int signal, int si_code) > + unsigned long address, int signal, int si_code, > + u32 pkey) > { > WARN_ON_ONCE(user_mode(regs)); > > @@ -735,8 +736,12 @@ kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code, > > set_signal_archinfo(address, error_code); > > - /* XXX: hwpoison faults will set the wrong code. */ > - force_sig_fault(signal, si_code, (void __user *)address); > + if (si_code == SEGV_PKUERR) { > + force_sig_pkuerr((void __user *)address, pkey); > + } else { > + /* XXX: hwpoison faults will set the wrong code. */ > + force_sig_fault(signal, si_code, (void __user *)address); > + } > } > > /* > @@ -798,7 +803,8 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, > struct task_struct *tsk = current; > > if (!user_mode(regs)) { > - kernelmode_fixup_or_oops(regs, error_code, address, pkey, si_code); > + kernelmode_fixup_or_oops(regs, error_code, address, > + SIGSEGV, si_code, pkey); > return; > } > > @@ -930,7 +936,8 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, > { > /* Kernel mode? Handle exceptions or die: */ > if (!user_mode(regs)) { > - kernelmode_fixup_or_oops(regs, error_code, address, SIGBUS, BUS_ADRERR); > + kernelmode_fixup_or_oops(regs, error_code, address, > + SIGBUS, BUS_ADRERR, 0); > return; > } Could we please use ARCH_DEFAULT_PKEY instead of 0's in all these call sites? I just detest seeing mystery functions with lots of 0's and 1's as parameters.