linux-kernel - [PATCH] x86: fix initialization of 'l' bit in ldt descriptors

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Date:	Sun, 27 Jul 2008 08:42:32 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Glauber de Oliveira Costa <gcosta@...hat.com>
Subject: [PATCH] x86: fix initialization of 'l' bit in ldt descriptors

Make sure that fill_ldt() initializes the 'l' bit in the descriptor.
It always sets it to 0, ignoring 'lm' in user_desc, preserving original
x86_64 behaviour.

Previously it was leaving 'l' uninitialized.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Cc: Glauber de Oliveira Costa <gcosta@...hat.com>
---
 include/asm-x86/desc.h |    5 +++++
 1 file changed, 5 insertions(+)

diff -r c79984cfb996 include/asm-x86/desc.h
--- a/include/asm-x86/desc.h	Fri Jul 25 16:09:12 2008 -0700
+++ b/include/asm-x86/desc.h	Sun Jul 27 08:31:08 2008 -0700
@@ -24,6 +24,9 @@
 	desc->d = info->seg_32bit;
 	desc->g = info->limit_in_pages;
 	desc->base2 = (info->base_addr & 0xff000000) >> 24;
+	/* Don't allow setting of the lm bit. It is useless anyways
+	   because 64bit system calls require __USER_CS. */
+	desc->l = 0;
 }
 
 extern struct desc_ptr idt_descr;


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