linux-kernel - Re: [BUGFIX][PATCH 0/3] fix bug for /proc/kcore causes panic (Was: [Bugme-new] [Bug 13850] New: reading /proc/kcore causes oops

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Message-Id: <20090731162146.0c211a1e.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 31 Jul 2009 16:21:46 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Mike Smith <scgtrp@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	bugzilla-daemon@...zilla.kernel.org,
	bugme-daemon@...zilla.kernel.org,
	Amerigo Wang <xiyou.wangcong@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [BUGFIX][PATCH 0/3] fix bug for /proc/kcore causes panic  (Was:
 [Bugme-new] [Bug 13850] New: reading /proc/kcore causes oops

On Fri, 31 Jul 2009 16:07:48 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:

> On Wed, 29 Jul 2009 12:32:09 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> 
> > On Tue, 28 Jul 2009 22:46:56 -0400
> > Mike Smith <scgtrp@...il.com> wrote:
> > 
> > > > What's layout of memory does your server have ?
> > > The log I gave was from my desktop, so I'll assume you wanted that
> > > instead of the server:
> > > [mike: mike in ~]$ grep "System RAM" /proc/iomem
> > > 00010000-0009efff : System RAM
> > > 00100000-1dedffff : System RAM
> > > 
> > From this, your kernel's valid direct-map address range will be
> > 
> > c0010000-c009efff
> > c0100000-ddedffff
> > 
> Ok, I reproduced the bug on x86-32 and here is a fix.
> 
> I reproduced the bug on x86-32 host with mem=512M boot option.
> 
> As I expected, the bug is from holes in vmalloc area.
> (This hole means thera are a memory hole withing [start ...start+size-PAGE_SIZE) 
>  of valid vm_struct.)
> 
> For review, I divided all into 3 patches. all series will be reply to this email.
> 
A memo.

[1/3] fixes the bug in /dev/kmem, also.
      This causes machine check on my host (and one of cpu was disabled)
      # dd if=/dev/kmem of=/dev/null bs=1024 count=1048576 skip=3145728
      I hope all users of kmem are sane people...but the patch fixes this.
      (If kmem has to access IOREMAP area, please teach me .)

[2/3] fix for this /proc/kcore bug based on [1/3]

[3/3] fix for vread/vwrite race conditions.
      not related to this reproducable bug itself but a fix for potential bug.

Thanks,
-Kame




> Thanks,
> -Kame
> 
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