From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965854AbcCJLFo (ORCPT ); Thu, 10 Mar 2016 06:05:44 -0500 Received: from torg.zytor.com ([198.137.202.12]:38230 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965843AbcCJLFW (ORCPT ); Thu, 10 Mar 2016 06:05:22 -0500 Date: Thu, 10 Mar 2016 03:04:16 -0800 From: tip-bot for Andy Lutomirski Message-ID: Cc: oleg@redhat.com, peterz@infradead.org, andrew.cooper3@citrix.com, dvlasenk@redhat.com, luto@kernel.org, hpa@zytor.com, luto@amacapital.net, mingo@kernel.org, bp@alien8.de, linux-kernel@vger.kernel.org, brgerst@gmail.com, torvalds@linux-foundation.org, tglx@linutronix.de Reply-To: brgerst@gmail.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, tglx@linutronix.de, andrew.cooper3@citrix.com, dvlasenk@redhat.com, oleg@redhat.com, peterz@infradead.org, luto@kernel.org, hpa@zytor.com, mingo@kernel.org, luto@amacapital.net, bp@alien8.de In-Reply-To: <6ff9a806f39098b166dc2c41c1db744df5272f29.1457578375.git.luto@kernel.org> References: <6ff9a806f39098b166dc2c41c1db744df5272f29.1457578375.git.luto@kernel.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/asm] x86/entry/32: Add and check a stack canary for the SYSENTER stack Git-Commit-ID: 2a41aa4feb25af3ead60b740c43df80c576efea2 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 2a41aa4feb25af3ead60b740c43df80c576efea2 Gitweb: http://git.kernel.org/tip/2a41aa4feb25af3ead60b740c43df80c576efea2 Author: Andy Lutomirski AuthorDate: Wed, 9 Mar 2016 19:00:33 -0800 Committer: Ingo Molnar CommitDate: Thu, 10 Mar 2016 09:48:14 +0100 x86/entry/32: Add and check a stack canary for the SYSENTER stack The first instruction of the SYSENTER entry runs on its own tiny stack. That stack can be used if a #DB or NMI is delivered before the SYSENTER prologue switches to a real stack. We have code in place to prevent us from overflowing the tiny stack. For added paranoia, add a canary to the stack and check it in do_debug() -- that way, if something goes wrong with the #DB logic, we'll eventually notice. Signed-off-by: Andy Lutomirski Cc: Andrew Cooper Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/6ff9a806f39098b166dc2c41c1db744df5272f29.1457578375.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/include/asm/processor.h | 3 ++- arch/x86/kernel/process.c | 3 +++ arch/x86/kernel/traps.c | 8 ++++++++ 3 files changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 7cd01b7..50a6dc8 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -299,8 +299,9 @@ struct tss_struct { #ifdef CONFIG_X86_32 /* - * Space for the temporary SYSENTER stack: + * Space for the temporary SYSENTER stack. */ + unsigned long SYSENTER_stack_canary; unsigned long SYSENTER_stack[64]; #endif diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 9f7c21c..ee9a979 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -57,6 +57,9 @@ __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = { */ .io_bitmap = { [0 ... IO_BITMAP_LONGS] = ~0 }, #endif +#ifdef CONFIG_X86_32 + .SYSENTER_stack_canary = STACK_END_MAGIC, +#endif }; EXPORT_PER_CPU_SYMBOL(cpu_tss); diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index b0ddb819..49e2e77 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -713,6 +713,14 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) debug_stack_usage_dec(); exit: +#if defined(CONFIG_X86_32) + /* + * 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"); +#endif ist_exit(regs); } NOKPROBE_SYMBOL(do_debug);