linux-kernel - Re: [PATCH 2.6.24] Add new string functions strict_strto* and convert kernel params to use them, take 2

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Date:	Thu, 31 Jan 2008 23:36:26 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	yi.y.yang@...el.com
Cc:	gregkh@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.24] Add new string functions strict_strto* and
 convert kernel params to use them, take 2

On Fri, 01 Feb 2008 06:11:43 +0800 Yi Yang <yi.y.yang@...el.com> wrote:

> This patch is a resend, it changes previous name "real_" to "strict_" 
> according to Randy Dunlap's feedback. Please consider to apply. thanks.
> 
> Currently, for every sysfs node, the callers will be responsible for
> implementing store operation, so many many callers are doing duplicate
> things to validate input, they have the same mistakes because they are
> calling simple_strtol/ul/ll/uul, especially for module params, they are
> just numeric, but you can echo such values as 0x1234xxx, 07777888 and
> 1234aaa, for these cases, module params store operation just ignores
> succesive invalid char and converts prefix part to a numeric although
> input is acctually invalid.
> 
> This patch tries to fix the aforementioned issues and implements strict_strtox
> serial functions, kernel/params.c uses them to strictly validate input,
> so module params will reject such values as 0x1234xxxx and returns an error:
> 
> write error: Invalid argument
> 
> Any modules which export numeric sysfs node can use strict_strtox instead of
> simple_strtox to reject any invalid input.
> 
> Here are some test results:
> 
> Before applying this patch:
> 
> [root@...gyi-dev /]# cat /sys/module/e1000/parameters/copybreak
> 4096
> [root@...gyi-dev /]# echo 0x1000 > /sys/module/e1000/parameters/copybreak
> [root@...gyi-dev /]# cat /sys/module/e1000/parameters/copybreak
> 4096
> [root@...gyi-dev /]# echo 0x1000g > /sys/module/e1000/parameters/copybreak
> [root@...gyi-dev /]# cat /sys/module/e1000/parameters/copybreak
> 4096
> [root@...gyi-dev /]# echo 0x1000gggggggg > /sys/module/e1000/parameters/copybreak
> [root@...gyi-dev /]# cat /sys/module/e1000/parameters/copybreak
> 4096
> [root@...gyi-dev /]# echo 010000 > /sys/module/e1000/parameters/copybreak
> [root@...gyi-dev /]# cat /sys/module/e1000/parameters/copybreak
> 4096
> [root@...gyi-dev /]# echo 0100008 > /sys/module/e1000/parameters/copybreak
> [root@...gyi-dev /]# cat /sys/module/e1000/parameters/copybreak
> 4096
> [root@...gyi-dev /]# echo 010000aaaaa > /sys/module/e1000/parameters/copybreak
> [root@...gyi-dev /]# cat /sys/module/e1000/parameters/copybreak
> 4096
> [root@...gyi-dev /]#
> 
> 
> After applying this patch:
> 
> [root@...gyi-dev /]# cat /sys/module/e1000/parameters/copybreak
> 4096
> [root@...gyi-dev /]# echo 0x1000 > /sys/module/e1000/parameters/copybreak
> [root@...gyi-dev /]# cat /sys/module/e1000/parameters/copybreak
> 4096
> [root@...gyi-dev /]# echo 0x1000g > /sys/module/e1000/parameters/copybreak
> -bash: echo: write error: Invalid argument
> [root@...gyi-dev /]# cat /sys/module/e1000/parameters/copybreak
> 4096
> [root@...gyi-dev /]# echo 0x1000gggggggg > /sys/module/e1000/parameters/copybreak
> -bash: echo: write error: Invalid argument
> [root@...gyi-dev /]# echo 010000 > /sys/module/e1000/parameters/copybreak
> [root@...gyi-dev /]# echo 0100008 > /sys/module/e1000/parameters/copybreak
> -bash: echo: write error: Invalid argument
> [root@...gyi-dev /]# echo 010000aaaaa > /sys/module/e1000/parameters/copybreak
> -bash: echo: write error: Invalid argument
> [root@...gyi-dev /]# cat /sys/module/e1000/parameters/copybreak
> 4096
> [root@...gyi-dev /]# echo -n 4096 > /sys/module/e1000/parameters/copybreak
> [root@...gyi-dev /]# cat /sys/module/e1000/parameters/copybreak
> 4096
> [root@...gyi-dev /]#
> 

Oh dear.  So if someone has an existing script which does

	echo 0x1000g > /sys/module/e1000/parameters/copybreak

we just broke their setup.

This is what happens when we screw up kernel interfaces: we should remain
bug-for-bug compatible with earlier releases.  argh, we suck :(

I'm inclined to merge it anyway - everyone already knows we suck, and
not many people will be affected and they suck too.

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