Re: [PATCH] ASoC: topology: Fix not to keep a reference to tplg fw

[Takashi Iwai <tiwai@suse.de>]

On Thu, 26 Nov 2015 12:01:23 +0100,
Mark Brown wrote:
> 
> On Thu, Nov 26, 2015 at 10:19:51AM +0100, Takashi Iwai wrote:
> > Vinod Koul wrote:
> 
> > > So in SKL, we do request firmware of topology binary and topology core uses
> > > that for strings here, so the patch 87b5ed8ec freed the topology binary
> > > which causes panic while accessing kcontrols.
> 
> > This is strange.  If it's about the kctl name string, the panic
> > shouldn't happen at accessing the kctl but at instantiating the kctl
> > from snd_kcontrol_new that contains the invalid string pointer.
> > The kctl object contains the string in itself, and there copies the
> > string from the template.
> 
> I guess it's possible that if the control creation happens soon enough
> after the memory is freed the data will still be valid.  This could be
> tested for by hacking things to deliberately trash the memory before we
> get to control creation.
> 
> > You really need to identify which path hits the issue exactly how.  In
> > general, the string passed to template is only for creating the kctl.
> > Once when kctl is created, the whole snd_kcontrol_new template and the
> > allocated string is no use, so they can be freed.
> 
> That does suggest a fairly simple fix of just holding on to the firmware
> for longer assuming that the analysis is correct.

Right, that would be the simplest fix.  Just assure that the whole f/w
image is kept until all objects are instantiated.


Takashi