linux-kernel - Re: [PATCH 2/3] devmem: check vmalloc address on kmem read/write

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Message-Id: <20090916115015.0aeddc01.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Wed, 16 Sep 2009 11:50:15 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, Tejun Heo <tj@...nel.org>,
	Nick Piggin <npiggin@...e.de>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: [PATCH 2/3] devmem: check vmalloc address on kmem read/write

On Wed, 16 Sep 2009 09:39:41 +0800
Wu Fengguang <fengguang.wu@...el.com> wrote:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
> 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.
> 
seems reasonable.

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

> CC: Greg Kroah-Hartman <gregkh@...e.de>
> CC: Hugh Dickins <hugh.dickins@...cali.co.uk>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
> ---
>  drivers/char/mem.c |    8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> --- linux-mm.orig/drivers/char/mem.c	2009-09-16 08:52:17.000000000 +0800
> +++ linux-mm/drivers/char/mem.c	2009-09-16 09:15:03.000000000 +0800
> @@ -443,6 +443,10 @@ static ssize_t read_kmem(struct file *fi
>  			return -ENOMEM;
>  		while (count > 0) {
>  			sz = size_inside_page(p, count);
> +			if (!is_vmalloc_or_module_addr((void *)p)) {
> +				err = -ENXIO;
> +				break;
> +			}
>  			err = vread(kbuf, (char *)p, sz);
>  			if (err)
>  				break;
> @@ -543,6 +547,10 @@ static ssize_t write_kmem(struct file * 
>  			unsigned long sz = size_inside_page(p, count);
>  			unsigned long n;
>  
> +			if (!is_vmalloc_or_module_addr((void *)p)) {
> +				err = -ENXIO;
> +				break;
> +			}
>  			n = copy_from_user(kbuf, buf, sz);
>  			if (n) {
>  				err = -EFAULT;
> 
> -- 
> 
> --
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