linux-kernel - Re: Faking MMIO ops? Fooling a driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4DFA4672.5080307@lwfinger.net>
Date:	Thu, 16 Jun 2011 13:07:46 -0500
From:	Larry Finger <Larry.Finger@...inger.net>
To:	Rafał Miłecki <zajec5@...il.com>
CC:	linux-wireless@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Pekka Paalanen <pq@....fi>
Subject: Re: Faking MMIO ops? Fooling a driver

On 06/16/2011 12:20 PM, Rafał Miłecki wrote:
> W dniu 16 czerwca 2011 16:44 użytkownik Rafał Miłecki
> <zajec5@...il.com>  napisał:
>> I analyze MMIO dumps of closed source driver and found such a place:
>> W 2 3855.911536 9 0xb06003fc 0x810 0x0 0
>> R 2 3855.911540 9 0xb06003fe 0x0 0x0 0
>> W 2 3855.911541 9 0xb06003fe 0x0 0x0 0
>>
>> After translation:
>>   phy_read(0x0810) ->  0x0000
>> phy_write(0x0810)<- 0x0000
>>
>> So it's quite obvious, the driver is reading PHY register, masking it
>> and writing masked value. Unfortunately from just looking at such
>> place we can not guess the mask driver uses.
>>
>> I'd like to fake value read from 0xb06003fe to be 0xFFFF.
>> Is there some ready method for doing such a trick?
>>
>> Dump comes from Kernel hacking → Tracers → MMIO and ndiswrapper.
>
> I can see values in MMIO trace struct are filled in
> arch/x86/mm/mmio-mod.c in "pre" and "post". However still no idea how
> to hack the returned value.
>
> Should I try hacking read[bwl] instead? :|

Probably. I do not see any way to trace and modify the results for a particular 
address without special code.

FYI, my reference driver for reverse engineering has no instance of a 
read/modify/write for PHY register 0x810. Is the code in question for a PHY type 
 > 6?

Larry
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/