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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 DF371ECDFB8 for ; Thu, 19 Jul 2018 23:39:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9978120856 for ; Thu, 19 Jul 2018 23:39:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9978120856 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zytor.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731035AbeGTAZV (ORCPT ); Thu, 19 Jul 2018 20:25:21 -0400 Received: from terminus.zytor.com ([198.137.202.136]:41267 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727553AbeGTAZV (ORCPT ); Thu, 19 Jul 2018 20:25:21 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id w6JNcqBO2454662 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 19 Jul 2018 16:38:52 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id w6JNcqim2454659; Thu, 19 Jul 2018 16:38:52 -0700 Date: Thu, 19 Jul 2018 16:38:52 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Joerg Roedel Message-ID: Cc: dvlasenk@redhat.com, boris.ostrovsky@oracle.com, David.Laight@aculab.com, llong@redhat.com, luto@kernel.org, hpa@zytor.com, jroedel@suse.de, peterz@infradead.org, pavel@ucw.cz, eduval@amazon.com, aarcange@redhat.com, jpoimboe@redhat.com, jgross@suse.com, mingo@kernel.org, bp@alien8.de, torvalds@linux-foundation.org, brgerst@gmail.com, dhgutteridge@sympatico.ca, linux-kernel@vger.kernel.org, will.deacon@arm.com, dave.hansen@intel.com, jkosina@suse.cz, tglx@linutronix.de, gregkh@linuxfoundation.org Reply-To: aarcange@redhat.com, jpoimboe@redhat.com, eduval@amazon.com, pavel@ucw.cz, hpa@zytor.com, peterz@infradead.org, jroedel@suse.de, David.Laight@aculab.com, luto@kernel.org, llong@redhat.com, boris.ostrovsky@oracle.com, dvlasenk@redhat.com, jkosina@suse.cz, dave.hansen@intel.com, will.deacon@arm.com, gregkh@linuxfoundation.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, dhgutteridge@sympatico.ca, brgerst@gmail.com, bp@alien8.de, mingo@kernel.org, jgross@suse.com, torvalds@linux-foundation.org In-Reply-To: <1531906876-13451-40-git-send-email-joro@8bytes.org> References: <1531906876-13451-40-git-send-email-joro@8bytes.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/pti] x86/entry/32: Add debug code to check entry/exit CR3 Git-Commit-ID: 97193702c6d353e12aefc0fb2f73a98ca421cd56 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 97193702c6d353e12aefc0fb2f73a98ca421cd56 Gitweb: https://git.kernel.org/tip/97193702c6d353e12aefc0fb2f73a98ca421cd56 Author: Joerg Roedel AuthorDate: Wed, 18 Jul 2018 11:41:16 +0200 Committer: Thomas Gleixner CommitDate: Fri, 20 Jul 2018 01:11:49 +0200 x86/entry/32: Add debug code to check entry/exit CR3 Add code to check whether the kernel is entered and left with the correct CR3 and make it depend on CONFIG_DEBUG_ENTRY. This is needed because there is no NX protection of user-addresses in the kernel-CR3 on x86-32 and that type of bug would not be detected otherwise. Signed-off-by: Joerg Roedel Signed-off-by: Thomas Gleixner Tested-by: Pavel Machek Cc: "H . Peter Anvin" Cc: linux-mm@kvack.org Cc: Linus Torvalds Cc: Andy Lutomirski Cc: Dave Hansen Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Jiri Kosina Cc: Boris Ostrovsky Cc: Brian Gerst Cc: David Laight Cc: Denys Vlasenko Cc: Eduardo Valentin Cc: Greg KH Cc: Will Deacon Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Cc: Andrea Arcangeli Cc: Waiman Long Cc: "David H . Gutteridge" Cc: joro@8bytes.org Link: https://lkml.kernel.org/r/1531906876-13451-40-git-send-email-joro@8bytes.org --- arch/x86/entry/entry_32.S | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index b1541c74c71a..010cdb41e3c7 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -166,6 +166,24 @@ .Lend_\@: .endm +.macro BUG_IF_WRONG_CR3 no_user_check=0 +#ifdef CONFIG_DEBUG_ENTRY + ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI + .if \no_user_check == 0 + /* coming from usermode? */ + testl $SEGMENT_RPL_MASK, PT_CS(%esp) + jz .Lend_\@ + .endif + /* On user-cr3? */ + movl %cr3, %eax + testl $PTI_SWITCH_MASK, %eax + jnz .Lend_\@ + /* From userspace with kernel cr3 - BUG */ + ud2 +.Lend_\@: +#endif +.endm + /* * Switch to kernel cr3 if not already loaded and return current cr3 in * \scratch_reg @@ -213,6 +231,8 @@ .macro SAVE_ALL_NMI cr3_reg:req SAVE_ALL + BUG_IF_WRONG_CR3 + /* * Now switch the CR3 when PTI is enabled. * @@ -224,6 +244,7 @@ .Lend_\@: .endm + /* * This is a sneaky trick to help the unwinder find pt_regs on the stack. The * frame pointer is replaced with an encoded pointer to pt_regs. The encoding @@ -287,6 +308,8 @@ .Lswitched_\@: + BUG_IF_WRONG_CR3 + RESTORE_REGS pop=\pop .endm @@ -357,6 +380,8 @@ ALTERNATIVE "", "jmp .Lend_\@", X86_FEATURE_XENPV + BUG_IF_WRONG_CR3 + SWITCH_TO_KERNEL_CR3 scratch_reg=%eax /* @@ -799,6 +824,7 @@ ENTRY(entry_SYSENTER_32) */ pushfl pushl %eax + BUG_IF_WRONG_CR3 no_user_check=1 SWITCH_TO_KERNEL_CR3 scratch_reg=%eax popl %eax popfl @@ -893,6 +919,7 @@ ENTRY(entry_SYSENTER_32) * whereas POPF does not.) */ btrl $X86_EFLAGS_IF_BIT, (%esp) + BUG_IF_WRONG_CR3 no_user_check=1 popfl popl %eax @@ -970,6 +997,8 @@ restore_all: /* Switch back to user CR3 */ SWITCH_TO_USER_CR3 scratch_reg=%eax + BUG_IF_WRONG_CR3 + /* Restore user state */ RESTORE_REGS pop=4 # skip orig_eax/error_code .Lirq_return: @@ -983,6 +1012,7 @@ restore_all: restore_all_kernel: TRACE_IRQS_IRET PARANOID_EXIT_TO_KERNEL_MODE + BUG_IF_WRONG_CR3 RESTORE_REGS 4 jmp .Lirq_return @@ -990,6 +1020,19 @@ restore_all_kernel: ENTRY(iret_exc ) pushl $0 # no error code pushl $do_iret_error + +#ifdef CONFIG_DEBUG_ENTRY + /* + * The stack-frame here is the one that iret faulted on, so its a + * return-to-user frame. We are on kernel-cr3 because we come here from + * the fixup code. This confuses the CR3 checker, so switch to user-cr3 + * as the checker expects it. + */ + pushl %eax + SWITCH_TO_USER_CR3 scratch_reg=%eax + popl %eax +#endif + jmp common_exception .previous _ASM_EXTABLE(.Lirq_return, iret_exc)