linux-kernel - Re: [PATCH 8/8] hwpoison: prevent /dev/kcore from accessing hwpoison pages

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Date:	Wed, 13 Jan 2010 22:23:57 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Andi Kleen <andi@...stfloor.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Nick Piggin <npiggin@...e.de>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH 8/8] hwpoison: prevent /dev/kcore from accessing
	hwpoison pages


Your $subject, I think you mean /proc/kcore...

On Wed, Jan 13, 2010 at 09:53:13PM +0800, Wu Fengguang wrote:
>Silently fill buffer with zeros when encounter hwpoison pages
>(accessing the hwpoison page content is deadly).
>
>This patch does not cover X86_32 - which has a dumb kern_addr_valid().
>It is unlikely anyone run a 32bit kernel will care about the hwpoison
>feature - its usable memory is limited.
>
>CC: Ingo Molnar <mingo@...e.hu>
>CC: Andi Kleen <andi@...stfloor.org> 
>CC: Pekka Enberg <penberg@...helsinki.fi>
>Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>

This patch looks fine for me.
Reviewed-by: WANG Cong <xiyou.wangcong@...il.com>

>---
> arch/x86/mm/init_64.c |   16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
>--- linux-mm.orig/arch/x86/mm/init_64.c	2010-01-13 21:23:04.000000000 +0800
>+++ linux-mm/arch/x86/mm/init_64.c	2010-01-13 21:25:32.000000000 +0800
>@@ -825,6 +825,7 @@ int __init reserve_bootmem_generic(unsig
> int kern_addr_valid(unsigned long addr)
> {
> 	unsigned long above = ((long)addr) >> __VIRTUAL_MASK_SHIFT;
>+	unsigned long pfn;
> 	pgd_t *pgd;
> 	pud_t *pud;
> 	pmd_t *pmd;
>@@ -845,14 +846,23 @@ int kern_addr_valid(unsigned long addr)
> 	if (pmd_none(*pmd))
> 		return 0;
> 
>-	if (pmd_large(*pmd))
>-		return pfn_valid(pmd_pfn(*pmd));
>+	if (pmd_large(*pmd)) {
>+		pfn = pmd_pfn(*pmd);
>+		pfn += pte_index(addr);
>+		goto check_pfn;
>+	}
> 
> 	pte = pte_offset_kernel(pmd, addr);
> 	if (pte_none(*pte))
> 		return 0;
> 
>-	return pfn_valid(pte_pfn(*pte));
>+	pfn = pte_pfn(*pte);
>+check_pfn:
>+	if (!pfn_valid(pfn))
>+		return 0;
>+	if (PageHWPoison(pfn_to_page(pfn)))
>+		return 0;
>+	return 1;
> }
> 
> /*
>
>
>--
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