On Tue, Jan 08, 2013 at 01:32:05AM +0100, Markus Grabner wrote:
> On Monday 07 January 2013 21:49:36 Mariusz Kozlowski wrote:
> > This is interesting. I tried a couple of times and it always worked.
> > When I send firmware version request using 'raw data communication'
> > interface POD responds correctly with firmware version and the driver
> > completes initialisation - alsa devices are registered and usable.
> > So this is pretty cool. There is some hope ... ;) Please see attached
> > line6-4.log with my comments inlined there.
> Ok, so there doesn't remain much code to check then :-) At first sight, the 
> statement "kfree(buffer);" in "line6_version_request_async" could be a 
> problem. Can you comment it out just for testing? This creates a memory leak, 
> but shouldn't cause any troubles otherwise.

Good news :) This fixes the initialisation problem. After first firmware
request POD responds correctly with firmware version and alsa interface
gets registered. I tried that on current trunk HEAD.

I'm looking at this code and wondering why it works. Because if we free
memory before it really gets send then this should be visible on any
hardware ... unless this is tight race and for some reason you do not
observe this on your computer. Also I never got any use-after-free
etc... but on the other hand I use stock ubuntu kernel so maybe most of
checks are disabled. I wonder is some magic debugging options would show
that on custom build kernel. Freed memory poisoning might not work as
this is just data - not pointer that would get dereferenced. So the
pointer would be valid but not the memory itself that it points to.
Interesting anyway.

So please prepare final fix and I'll test it :) I think mainline needs
that fix as well.

Thanks,
-- 
Mariusz Kozlowski

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