From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752807AbZFFSXe (ORCPT ); Sat, 6 Jun 2009 14:23:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751380AbZFFSX0 (ORCPT ); Sat, 6 Jun 2009 14:23:26 -0400 Received: from norkia.v3.sk ([92.240.234.41]:44882 "EHLO norkia.v3.sk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751131AbZFFSXZ (ORCPT ); Sat, 6 Jun 2009 14:23:25 -0400 Subject: [PATCH] Fix non-lazy GS handling in sys_vm86() From: Lubomir Rintel To: Tejun Heo , Andrew Morton , Linux Kernel Mailing List , x86@kernel.org Content-Type: text/plain Date: Sat, 06 Jun 2009 20:23:25 +0200 Message-Id: <1244312605.28613.4.camel@bimbo> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 (2.26.1-2.fc11) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This fixes a stack corruption panic or null dereference oops due to a bad GS in resume_userspace() when returning from sys_vm86() and calling lockdep_sys_exit(). Only a problem when CONFIG_LOCKDEP and CONFIG_CC_STACKPROTECTOR enabled. Signed-off-by: Lubomir Rintel --- arch/x86/kernel/vm86_32.c | 13 +++++++------ 1 files changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c index d7ac84e..177d976 100644 --- a/arch/x86/kernel/vm86_32.c +++ b/arch/x86/kernel/vm86_32.c @@ -287,10 +287,9 @@ static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk info->regs.pt.ds = 0; info->regs.pt.es = 0; info->regs.pt.fs = 0; - -/* we are clearing gs later just before "jmp resume_userspace", - * because it is not saved/restored. - */ +#ifndef CONFIG_X86_32_LAZY_GS + info->regs.pt.gs = 0; +#endif /* * The flags register is also special: we cannot trust that the user @@ -343,10 +342,12 @@ static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk __asm__ __volatile__( "movl %0,%%esp\n\t" "movl %1,%%ebp\n\t" - "mov %2, %%gs\n\t" +#ifdef CONFIG_X86_32_LAZY_GS + "mov $0, %%gs\n\t" +#endif "jmp resume_userspace" : /* no outputs */ - :"r" (&info->regs), "r" (task_thread_info(tsk)), "r" (0)); + :"r" (&info->regs), "r" (task_thread_info(tsk))); /* we never return here */ } -- "Excuse all the blood" -- Dead