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[PATCH] x86/ldt: correct ldt access in single stepping logic

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From	Juergen Gross <jgross@suse.com>
Newsgroups	linux.kernel
Subject	[PATCH] x86/ldt: correct ldt access in single stepping logic
Date	Thu, 06 Aug 2015 10:10:02 +0200
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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 *.

Cc: <stable@vger.kernel.org> # 37868fe113ff: x86/ldt: Make modify_ldt synchronous
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 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 6273324..0ccb53a 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];
-- 
2.1.4

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[PATCH] x86/ldt: correct ldt access in single stepping logic Juergen Gross <jgross@suse.com> - 2015-08-06 10:10 +0200
  Re: [PATCH] x86/ldt: correct ldt access in single stepping logic Andy Lutomirski <luto@amacapital.net> - 2015-08-06 20:40 +0200
  [tip:x86/urgent] x86/ldt:   Correct LDT access in single stepping logic tip-bot for Juergen Gross <tipbot@zytor.com> - 2015-08-09 12:30 +0200

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