From 3aa6b186f86c5d06d6d92d14311ffed51f091f40 Mon Sep 17 00:00:00 2001 From: Lubomir Rintel <lkundrak@v3.sk> Date: Sun, 7 Jun 2009 16:23:48 +0200 Subject: [PATCH] x86: Fix non-lazy GS handling in sys_vm86() 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 <lkundrak@v3.sk> Cc: H. Peter Anvin <hpa@zytor.com> LKML-Reference: <1244384628.2323.4.camel@bimbo> Signed-off-by: Ingo Molnar <mingo@elte.hu> --- arch/x86/kernel/vm86_32.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c index d7ac84e7fc1c7..6a177694058fe 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 @@ -343,7 +342,9 @@ 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" +#ifdef CONFIG_X86_32_LAZY_GS "mov %2, %%gs\n\t" +#endif "jmp resume_userspace" : /* no outputs */ :"r" (&info->regs), "r" (task_thread_info(tsk)), "r" (0));