linux-kernel - Re: [stable] [PATCH] devmem: check vmalloc address on kmem read/write

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Message-Id: <20100204122742.2e1c38f8.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 4 Feb 2010 12:27:42 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Greg KH <greg@...ah.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	Andi Kleen <andi@...stfloor.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"stable@...nel.org" <stable@...nel.org>,
	"juha_motorsportcom@...kku.com" <juha_motorsportcom@...kku.com>
Subject: Re: [stable] [PATCH] devmem: check vmalloc address on kmem
 read/write

On Thu, 4 Feb 2010 11:18:54 +0800
Wu Fengguang <fengguang.wu@...el.com> wrote:

> On Thu, Feb 04, 2010 at 10:58:01AM +0800, KAMEZAWA Hiroyuki wrote:
> > On Thu, 4 Feb 2010 10:42:02 +0800
> > Wu Fengguang <fengguang.wu@...el.com> wrote:
> > 
> > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > > 
> > > commit 325fda71d0badc1073dc59f12a948f24ff05796a upstream.
> > > 
> > > Otherwise vmalloc_to_page() will BUG().
> > > 
> > > This also makes the kmem read/write implementation aligned with mem(4):
> > > "References to nonexistent locations cause errors to be returned." Here
> > > we return -ENXIO (inspired by Hugh) if no bytes have been transfered
> > > to/from user space, otherwise return partial read/write results.
> > > 
> > 
> > Wu-san, I have additonal fix to this patch. Now, *ppos update is unstable..
> > Could you make merged one ?
> > Maybe this one makes the all behavior clearer.
> > 
> > ==
> > This is a more fix for devmem-check-vmalloc-address-on-kmem-read-write.patch
> > Now, the condition for updating *ppos is not good. (it's updated even if EFAULT
> > occurs..). This fixes that.
> > 
> > 
> > Reported-by: "Juha Leppanen" <juha_motorsportcom@...kku.com>
> 
> Sorry, can you elaborate the problem? How it break the application?
> 
> It looks that do_generic_file_read() also updates *ppos progressively,
> no one complains about that.
> 
Ah...it seems I misunderstood something...ok, *ppos should be updated every time.

I startted from adding comment on following line and got into a maze.

>   return (virtr + wrote) ? : err;

Sorry for noise.

-Kame

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