From patchwork Wed Nov 4 14:54:23 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jarkko Sakkinen X-Patchwork-Id: 11880861 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=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 7727EC388F9 for ; Wed, 4 Nov 2020 14:56:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B10620729 for ; Wed, 4 Nov 2020 14:56:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730485AbgKDO4a (ORCPT ); Wed, 4 Nov 2020 09:56:30 -0500 Received: from mail.kernel.org ([198.145.29.99]:50372 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727651AbgKDO42 (ORCPT ); Wed, 4 Nov 2020 09:56:28 -0500 Received: from suppilovahvero.lan (83-245-197-237.elisa-laajakaista.fi [83.245.197.237]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8D15120729; Wed, 4 Nov 2020 14:56:21 +0000 (UTC) From: Jarkko Sakkinen To: x86@kernel.org, linux-sgx@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Sean Christopherson , Jethro Beekman , Jarkko Sakkinen , akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com, asapek@google.com, bp@alien8.de, cedric.xing@intel.com, chenalexchen@google.com, conradparker@google.com, cyhanish@google.com, dave.hansen@intel.com, haitao.huang@intel.com, kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com, ludloff@google.com, luto@kernel.org, nhorman@redhat.com, npmccallum@redhat.com, puiterwijk@redhat.com, rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com, mikko.ylinen@intel.com Subject: [PATCH v40 17/24] x86/fault: Add helper function to sanitize error code Date: Wed, 4 Nov 2020 16:54:23 +0200 Message-Id: <20201104145430.300542-18-jarkko.sakkinen@linux.intel.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20201104145430.300542-1-jarkko.sakkinen@linux.intel.com> References: <20201104145430.300542-1-jarkko.sakkinen@linux.intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org From: Sean Christopherson vDSO exception fixup is a replacement for signals in limited situations. Signals and vDSO exception fixup need to provide similar information to userspace, including the hardware error code. That hardware error code needs to be sanitized. For instance, if userspace accesses a kernel address, the error code could indicate to userspace whether the address had a Present=1 PTE. That can leak information about the kernel layout to userspace, which is bad. The existing signal code does this sanitization, but fairly late in the signal process. The vDSO exception code runs before the sanitization happens. Move error code sanitization out of the signal code and into a helper. Call the helper in the signal code. Acked-by: Jethro Beekman Signed-off-by: Sean Christopherson Signed-off-by: Jarkko Sakkinen --- Changes from v39: * Add the missing change to the set_signal_archinfo() that removes the snippet contained in sanitize_error_code(). arch/x86/mm/fault.c | 26 ++++++++++++++------------ 1 file changed, 14 insertions(+), 12 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 9339fee83784..0161d4acf3ad 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -602,11 +602,9 @@ pgtable_bad(struct pt_regs *regs, unsigned long error_code, oops_end(flags, regs, sig); } -static void set_signal_archinfo(unsigned long address, - unsigned long error_code) +static void sanitize_error_code(unsigned long address, + unsigned long *error_code) { - struct task_struct *tsk = current; - /* * To avoid leaking information about the kernel page * table layout, pretend that user-mode accesses to @@ -617,7 +615,13 @@ static void set_signal_archinfo(unsigned long address, * information and does not appear to cause any problems. */ if (address >= TASK_SIZE_MAX) - error_code |= X86_PF_PROT; + *error_code |= X86_PF_PROT; +} + +static void set_signal_archinfo(unsigned long address, + unsigned long error_code) +{ + struct task_struct *tsk = current; tsk->thread.trap_nr = X86_TRAP_PF; tsk->thread.error_code = error_code | X86_PF_USER; @@ -658,6 +662,8 @@ no_context(struct pt_regs *regs, unsigned long error_code, * faulting through the emulate_vsyscall() logic. */ if (current->thread.sig_on_uaccess_err && signal) { + sanitize_error_code(address, &error_code); + set_signal_archinfo(address, error_code); /* XXX: hwpoison faults will set the wrong code. */ @@ -806,13 +812,7 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, if (is_errata100(regs, address)) return; - /* - * To avoid leaking information about the kernel page table - * layout, pretend that user-mode accesses to kernel addresses - * are always protection faults. - */ - if (address >= TASK_SIZE_MAX) - error_code |= X86_PF_PROT; + sanitize_error_code(address, &error_code); if (likely(show_unhandled_signals)) show_signal_msg(regs, error_code, address, tsk); @@ -931,6 +931,8 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, if (is_prefetch(regs, error_code, address)) return; + sanitize_error_code(address, &error_code); + set_signal_archinfo(address, error_code); #ifdef CONFIG_MEMORY_FAILURE