linux-kernel - Re: [PATCH RESEND] early_ioremap has a fencepost error

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Date:	Fri, 10 Oct 2008 12:21:28 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Greg KH <greg@...ah.com>, stable@...nel.org, torvalds@...l.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Yinghai Lu <yinghai@...nel.org>
Subject: Re: [PATCH RESEND] early_ioremap has a fencepost error


* Alan Cox <alan@...rguk.ukuu.org.uk> wrote:

> Can we get this into 2.6.27.x at some point as its a regression and a 
> crash on boot for some users moving from 2.6.26

yes, have your fix patch from yesterday in tip/x86/urgent already, with 
a stable@...nel.org tag included as well - see below. Thanks Alan!

	Ingo

-------------->
>From dd5698f42a5f2b494c3e811598403f105b00f4f2 Mon Sep 17 00:00:00 2001
From: Alan Cox <alan@...hat.com>
Date: Fri, 10 Oct 2008 10:46:45 +0100
Subject: [PATCH] x86, early_ioremap: fix fencepost error

The x86 implementation of early_ioremap has an off by one error. If we get
an object which ends on the first byte of a page we undermap by one page and
this causes a crash on boot with the ASUS P5QL whose DMI table happens to fit
this alignment.

The size computation is currently

	last_addr = phys_addr + size - 1;
	npages = (PAGE_ALIGN(last_addr) - phys_addr)

(Consider a request for 1 byte at alignment 0...)

Closes #11693

Debugging work by Ian Campbell/Felix Geyer

Signed-off-by: Alan Cox <alan@...at.com>
Cc: <stable@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 arch/x86/mm/ioremap.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index d4b6e6a..d0975fc 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -595,7 +595,7 @@ void __init *early_ioremap(unsigned long phys_addr, unsigned long size)
 	 */
 	offset = phys_addr & ~PAGE_MASK;
 	phys_addr &= PAGE_MASK;
-	size = PAGE_ALIGN(last_addr) - phys_addr;
+	size = PAGE_ALIGN(last_addr + 1) - phys_addr;
 
 	/*
 	 * Mappings have to fit in the FIX_BTMAP area.
--
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