From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752841AbdLDQvh (ORCPT ); Mon, 4 Dec 2017 11:51:37 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:59903 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752559AbdLDQvJ (ORCPT ); Mon, 4 Dec 2017 11:51:09 -0500 Message-Id: <20171204150606.572577316@linutronix.de> User-Agent: quilt/0.63-1 Date: Mon, 04 Dec 2017 15:07:27 +0100 From: Thomas Gleixner To: LKML Cc: x86@kernel.org, Linus Torvalds , Andy Lutomirsky , Peter Zijlstra , Dave Hansen , Borislav Petkov , Greg KH , keescook@google.com, hughd@google.com, Brian Gerst , Josh Poimboeuf , Denys Vlasenko , Rik van Riel , Boris Ostrovsky , Juergen Gross , David Laight , Eduardo Valentin , aliguori@amazon.com, Will Deacon , daniel.gruss@iaik.tugraz.at, Ingo Molnar , Borislav Petkov , Dave Hansen Subject: [patch 21/60] x86/entry/64: Remove the SYSENTER stack canary References: <20171204140706.296109558@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Disposition: inline; filename=x86-entry-64--Remove_the_SYSENTER_stack_canary.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andy Lutomirski Now that the SYSENTER stack has a guard page, there's no need for a canary to detect overflow after the fact. Signed-off-by: Andy Lutomirski Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner Reviewed-by: Thomas Gleixner Reviewed-by: Borislav Petkov Cc: Rik van Riel Cc: Denys Vlasenko Cc: Peter Zijlstra Cc: Brian Gerst Cc: Dave Hansen Cc: Josh Poimboeuf Cc: Linus Torvalds Link: https://lkml.kernel.org/r/be3179c0a38c392fa44ebeb7dd89391ff5c010c3.1511497875.git.luto@kernel.org --- arch/x86/include/asm/processor.h | 1 - arch/x86/kernel/dumpstack.c | 3 +-- arch/x86/kernel/process.c | 1 - arch/x86/kernel/traps.c | 7 ------- 4 files changed, 1 insertion(+), 11 deletions(-) --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -342,7 +342,6 @@ struct tss_struct { * Space for the temporary SYSENTER stack, used for SYSENTER * and the entry trampoline as well. */ - unsigned long SYSENTER_stack_canary; unsigned long SYSENTER_stack[64]; /* --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -48,8 +48,7 @@ bool in_sysenter_stack(unsigned long *st int cpu = smp_processor_id(); struct tss_struct *tss = &get_cpu_entry_area(cpu)->tss; - /* Treat the canary as part of the stack for unwinding purposes. */ - void *begin = &tss->SYSENTER_stack_canary; + void *begin = &tss->SYSENTER_stack; void *end = (void *)&tss->SYSENTER_stack + sizeof(tss->SYSENTER_stack); if ((void *)stack < begin || (void *)stack >= end) --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -81,7 +81,6 @@ */ .io_bitmap = { [0 ... IO_BITMAP_LONGS] = ~0 }, #endif - .SYSENTER_stack_canary = STACK_END_MAGIC, }; EXPORT_PER_CPU_SYMBOL(cpu_tss); --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -819,13 +819,6 @@ dotraplinkage void do_debug(struct pt_re debug_stack_usage_dec(); exit: - /* - * This is the most likely code path that involves non-trivial use - * of the SYSENTER stack. Check that we haven't overrun it. - */ - WARN(this_cpu_read(cpu_tss.SYSENTER_stack_canary) != STACK_END_MAGIC, - "Overran or corrupted SYSENTER stack\n"); - ist_exit(regs); } NOKPROBE_SYMBOL(do_debug);