ld.so.preload of libmediaclient.so is *very* harmful

c.hoffmann at bnet.at c.hoffmann at bnet.at
Fri Feb 4 01:46:23 MST 2011

I didn´t take a closer look to what the sundtek driver did to my system
since I didn´t run into problems before.
For now I have to live with the LD_PRELOAD option since I need the driver
for my vdr.

Thanks for your help, hopefully sundtek will adapt their driver for future

On Fri, 04 Feb 2011 14:10:24 +1100, Andrew Bartlett <abartlet at samba.org>
> On Thu, 2011-02-03 at 13:28 +0100, c.hoffmann at bnet.at wrote:
>> Could finish provision!
>> There was a problem with the libmediaclient.so which is installed with
> the
>> driver for my tv-card (sundtek) I am using.
>> Deinstalled the driver and did provision again, this time it worked!
>> Reinstall the driver and it hopefully does not interfere with samba4.
>> br
> After a very good guess by tridge, I found:
> http://www.sundtek.com/support/install.sh.txt
> This script, which I presume you used, modifies /etc/ld.so.preload, and
> causes libmediaclient.so to be preloaded into every single process on
> the system.  Any process that calls net_read() will call into your TV
> card driver, and will break badly.
> You are lucky that you only got a hang, as the preloading (equivalent to
> LD_PRELOAD set over every program on the system) of Sundtek's
> libmediaclient.so could easily have caused a segfault, or simply random
> data corruption.
> I suggest you never install this library on any system for which you
> care for it's integrity.  Once loaded, this library can override any
> function in any program, with all the checks overridden.  We have taken
> considerable care to ensure that we don't use random library functions,
> but cannot prevent a preload.
> I've observed other backtraces on the net showing this library providing
> functions as basic as 'poll', so even avoiding using a function by this
> particular name won't help.
> You could, as suggested in the sundtek forums, simply load this library
> for the only particular applications you need using LD_PRELOAD, but I
> would simply recommend avoiding this code entirely.
> Andrew Bartlett
> --
> Andrew Bartlett                               
> Authentication Developer, Samba Team           http://samba.org
> Samba Developer, Cisco Inc.

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