Re: [PATCH] ALSA: hda: fix NULL pointer dereference during suspend

[Takashi Iwai <tiwai@suse.de>]

On Wed, 29 Jul 2020 17:03:22 +0200,
Ranjani Sridharan wrote:
> 
> On Wed, 2020-07-29 at 09:48 +0200, Takashi Iwai wrote:
> > On Wed, 29 Jul 2020 01:10:11 +0200,
> > Ranjani Sridharan wrote:
> > > When the ASoC card registration fails and the codec component
> > > driver
> > > never probes, the codec device is not initialized and therefore
> > > memory for codec->wcaps is not allocated. This results in a NULL
> > > pointer
> > > dereference when the codec driver suspend callback is invoked
> > > during
> > > system suspend. Fix this by returning without performing any
> > > actions
> > > during codec suspend/resume if the card was not registered
> > > successfully.
> > > 
> > > Reviewed-by: Pierre-Louis Bossart <
> > > pierre-louis.bossart@linux.intel.com>
> > > Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com
> > > >
> > 
> > The code changes look OK to apply, but I still wonder how the runtime
> > PM gets invoked even if the device is not instantiated properly?
> Hi Takashi,
> 
> Its not runtime PM suspend but rather the system PM suspend callback
> that is invoked when the system is suspended that ends up callling the
> the runtime PM callback. So, the sequence is:
> hda_codec_pm_suspend()
>    -> pm_runtime_force_suspend()
>           -> hda_codec_runtime_suspend()

OK, but the problem is still same.  The basic problem is that the
hda_codec_driver_probe() is called for the hda_codec object that
hasn't been initialized and bypasses to ext_ops.hdev_attach.

So, we can factor out the fundamental part of
snd_hda_codec_device_new() that is irrelevant with the card object and
call it in hdac_hda_dev_probe().  Most of the legacy HD-audio codec
can work without the card object, including suspend/resume.

But this will be a more intensive surgery, and maybe not much worth
for the corner case, so I already applied your patch as is.


thanks,

Takashi