Re: [PATCH] net: fix /proc/net/snmp as memory corruptor

[Alexey Dobriyan <adobriyan@gmail.com>]

On Sat, Nov 08, 2008 at 06:53:31AM +0100, Eric Dumazet wrote:
> Alexey Dobriyan a écrit :
>> On Sat, Nov 08, 2008 at 05:52:56AM +0300, Alexey Dobriyan wrote:
>>> On Sat, Nov 08, 2008 at 04:02:37AM +0300, Alexey Dobriyan wrote:
>>>> On Sat, Nov 08, 2008 at 01:22:08AM +0100, Eric Sesterhenn wrote:
>>>>> running a bunch of network related stresstests (isic, isicng, 
>>>>> ...) and trying to read all files in /proc afterwards gave me two
>>>>> oopses. I was able to reproduce them on another box with
>>>>> a different config. I was able to reproduce this on 2.6.24 too,
>>>>> so this is no regression. The icmpsic is version 0.06. The 
>>>>> minimal testcase to trigger this:
>>>>>
>>>>> ------------8<----------------
>>>>> #!/bin/bash
>>>>>
>>>>> icmpsic -s 127.0.0.1 -d 127.0.0.1 -p 100000
>>>>>
>>>>> find /proc/net/ | xargs cat > /dev/null
>>>>>
>>>>> cat /proc/net/ip_mr_cache
>>>>> cat /proc/net/ip_mr_vif
>>>>> ------------8<----------------
>>>>>
>>>>>
>>>>> root@computer-desktop:~/testing# cat /proc/338/net/ip_mr_cache
>>>>>
>>>>> [ 1572.702100] BUG: unable to handle kernel NULL pointer dereferenceat 000001c1
>>>>> [ 1572.702588] IP: [<c05942c6>] ipmr_mfc_seq_show+0x26/0xf0
>>>> Reproduced.
>>> 	icmpsic -s 127.0.0.1 -d 127.0.0.1 -p 100000
>>> 	cat /proc/net/snmp				# sic
>>> 	cat /proc/net/ip_mr_cache
>>>
>>> mfc_cache_array is full of small integers
>>>
>>> 	[0] = 0x1a8
>>> 	[1] = 0x1a9
>>>
>>> and so on.
>>
>> OK, this minimally fixes mfc_cache_array corruption.
>>
>> Someone was scared of 16 integers on stack. :^)
>
> Good spot Alexey :)

This patch works too.