From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754552AbeBNHjQ (ORCPT ); Wed, 14 Feb 2018 02:39:16 -0500 Received: from mail-wm0-f67.google.com ([74.125.82.67]:34122 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754489AbeBNHjP (ORCPT ); Wed, 14 Feb 2018 02:39:15 -0500 X-Google-Smtp-Source: AH8x2253IjK/oFMmNtU3TMAhAKPcb+/VBCjFLfsg2EVxAxTv5ue9TjTdms/Y4Q5aW96Hr3KXr7G6hA== Date: Wed, 14 Feb 2018 08:39:11 +0100 From: Ingo Molnar To: Dave Hansen Cc: Josh Poimboeuf , x86@kernel.org, linux-kernel@vger.kernel.org, Andy Lutomirski , Peter Zijlstra , David Woodhouse , Thomas Gleixner , Linus Torvalds , Peter Zijlstra Subject: Re: [PATCH] x86/entry/64: Fix CR3 restore order in paranoid_exit() Message-ID: <20180214073910.boevmg65upbk3vqb@gmail.com> References: <2b8ce3a31bcdfffa434269f4abf5d46816b75773.1518575248.git.jpoimboe@redhat.com> <9f6d258e-8191-9b57-4839-aa7c84e4c829@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9f6d258e-8191-9b57-4839-aa7c84e4c829@intel.com> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Dave Hansen wrote: > On 02/13/2018 06:27 PM, Josh Poimboeuf wrote: > > --- a/arch/x86/entry/entry_64.S > > +++ b/arch/x86/entry/entry_64.S > > @@ -1167,10 +1167,10 @@ ENTRY(paranoid_exit) > > UNWIND_HINT_REGS > > DISABLE_INTERRUPTS(CLBR_ANY) > > TRACE_IRQS_OFF_DEBUG > > + RESTORE_CR3 scratch_reg=%r15 save_reg=%r14 > > testl %ebx, %ebx /* swapgs needed? */ > > jnz .Lparanoid_exit_no_swapgs > > TRACE_IRQS_IRETQ > > - RESTORE_CR3 scratch_reg=%rbx save_reg=%r14 > > SWAPGS_UNSAFE_STACK > > jmp .Lparanoid_exit_restore > > .Lparanoid_exit_no_swapgs: > > TRACE_IRQS_* call non-entry functions that are not mapped by the user > CR3. How can this possibly work? What am I missing? How about something like the patch below? (Totally untested) Thanks, Ingo --- arch/x86/entry/entry_64.S | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index cd216c9431e1..8971bd64d515 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1175,6 +1175,7 @@ ENTRY(paranoid_exit) jmp .Lparanoid_exit_restore .Lparanoid_exit_no_swapgs: TRACE_IRQS_IRETQ_DEBUG + RESTORE_CR3 scratch_reg=%rbx save_reg=%r14 .Lparanoid_exit_restore: jmp restore_regs_and_return_to_kernel END(paranoid_exit)