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

From: Eric Sesterhenn <[email-masked]>
Date: Sat, 8 Nov 2008 10:48:24 +0100

* Alexey Dobriyan ([email-masked]) wrote:
> 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.

Wow, that was fast :-) Also verified that the patch fixes the issue.

Thanks, Eric