linux-kernel - Re: [PATCH] sunrpc - fixup userspace buffer possible overrun v2

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Date:	Sun, 31 Aug 2008 16:09:10 +0200
From:	Ingo Oeser <ioe-lkml@...eria.de>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Vegard Nossum <vegard.nossum@...il.com>, bfields@...ldses.org,
	neilb@...e.de
Subject: Re: [PATCH] sunrpc - fixup userspace buffer possible overrun v2

Hi Cyrill,

On Sunday 31 August 2008, Cyrill Gorcunov wrote:
> The conclusion is that proc_do_xprt doesn't check for userside buffer
> size indeed so fix. Also set lenp to number of bytes were really written.

Why not use  simple_read_from_buffer() for the read case and
keep the -EINVAL for the write case.

> Reported-by: Vegard Nossum <vegard.nossum@...il.com>
> Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com>
> CC: David Wagner <daw@...berkeley.edu>
> ---
> 
> Please review.
> 
> Index: linux-2.6.git/net/sunrpc/sysctl.c
> ===================================================================
> --- linux-2.6.git.orig/net/sunrpc/sysctl.c	2008-08-31 13:43:46.000000000 +0400
> +++ linux-2.6.git/net/sunrpc/sysctl.c	2008-08-31 13:58:14.000000000 +0400
> @@ -60,23 +60,26 @@ static int proc_do_xprt(ctl_table *table
>  			void __user *buffer, size_t *lenp, loff_t *ppos)
>  {
>  	char tmpbuf[256];
> -	int len;
> +	size_t len;
> +
+ ssize_t ret;
>  	if ((*ppos && !write) || !*lenp) {
>  		*lenp = 0;
>  		return 0;
>  	}
> +
>  	if (write)
>  		return -EINVAL;

        len = svc_print_xprts(tmpbuf, sizeof(tmpbuf));
	ret = simple_read_from_buffer(buffer, ppos, tmpbuf, len);
	if (ret >= 0) {
		*lenp = ret;
		ret = 0;
	}

	return ret;
   }


Best Regards

Ingo Oeser
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