From 136d9d83c07c5e30ac49fc83b27e8c4842f108fc Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Thu, 6 Aug 2015 10:04:38 +0200 Subject: [PATCH] x86/ldt: Correct LDT access in single stepping logic Commit 37868fe113ff ("x86/ldt: Make modify_ldt synchronous") introduced a new struct ldt_struct anchored at mm->context.ldt. convert_ip_to_linear() was changed to reflect this, but indexing into the ldt has to be changed as the pointer is no longer void *. Signed-off-by: Juergen Gross Reviewed-by: Andy Lutomirski Cc: # On top of: 37868fe113ff: x86/ldt: Make modify_ldt synchronous Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: bp@suse.de Link: http://lkml.kernel.org/r/1438848278-12906-1-git-send-email-jgross@suse.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/step.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c index 6273324186ac..0ccb53a9fcd9 100644 --- a/arch/x86/kernel/step.c +++ b/arch/x86/kernel/step.c @@ -28,11 +28,11 @@ unsigned long convert_ip_to_linear(struct task_struct *child, struct pt_regs *re struct desc_struct *desc; unsigned long base; - seg &= ~7UL; + seg >>= 3; mutex_lock(&child->mm->context.lock); if (unlikely(!child->mm->context.ldt || - (seg >> 3) >= child->mm->context.ldt->size)) + seg >= child->mm->context.ldt->size)) addr = -1L; /* bogus selector, access would fault */ else { desc = &child->mm->context.ldt->entries[seg]; -- 2.20.1