RE: [PATCH] ASoC: da7219: Fix general protection fault in da7219_register_dai_clks

[Adam Thomson <Adam.Thomson.Opensource@diasemi.com>]

On 30 July 2020 17:06, Yong Zhi wrote:
> >
> > > clkdev_drop(cl) does not null the removed cl, if
> > > da7219_register_dai_clks() entered again after card removal,
> > > devm_clk_register() will return -EEXIST, the goto err to clkdev_drop() will
> > trigger board reboot.
> > >
> > > Test commands:
> > >    modprobe -r snd_sof_pci
> > >    modprobe snd_sof_pci
> > >
> > > The oops looks like:
> > >
> > > da7219 i2c-DLGS7219:00: Using default DAI clk names: da7219-dai-wclk,
> > > da7219- dai-bclk
> > > da7219 i2c-DLGS7219:00: Failed to register da7219-dai-wclk: -17
> > > general protection fault: 0000 [#1] PREEMPT SMP NOPTI
> > > RIP: 0010:clkdev_drop+0x20/0x52
> > > Call Trace:
> > >  da7219_probe+0x52e/0x6dc [snd_soc_da7219]
> > >  soc_probe_component+0x206/0x3a1
> > >  snd_soc_bind_card+0x4ee/0x9a6
> > >  devm_snd_soc_register_card+0x48/0x7b
> > >  audio_probe+0x1f0/0x221 [snd_soc_sof_da7219_max98373]
> > >  platform_drv_probe+0x89/0xa2
> > >  really_probe+0x129/0x30d
> > >  driver_probe_device+0x59/0xec
> > >  ? driver_sysfs_remove+0x55/0x55
> > >  bus_for_each_drv+0xa1/0xdc
> > >  __device_attach+0xc2/0x146
> > >  bus_probe_device+0x32/0x97
> > >  device_add+0x311/0x3b4
> > >  platform_device_add+0x184/0x1eb
> > >
> > > Fix by marking (nullifying) the da7219->dai_clks_lookup[i] after
> > > clkdev_drop().
> > >
> > > Signed-off-by: Yong Zhi <yong.zhi@intel.com>
> > > ---
> > >  sound/soc/codecs/da7219.c | 4 +++-
> > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/sound/soc/codecs/da7219.c b/sound/soc/codecs/da7219.c
> > > index 153ea30b5a8f..54da7cfbb5f4 100644
> > > --- a/sound/soc/codecs/da7219.c
> > > +++ b/sound/soc/codecs/da7219.c
> > > @@ -2369,8 +2369,10 @@ static void da7219_remove(struct
> > > snd_soc_component *component)
> > >
> > >  #ifdef CONFIG_COMMON_CLK
> > >  	for (i = DA7219_DAI_NUM_CLKS - 1; i >= 0; --i) {
> > > -		if (da7219->dai_clks_lookup[i])
> > > +		if (da7219->dai_clks_lookup[i]) {
> > >  			clkdev_drop(da7219->dai_clks_lookup[i]);
> > > +			da7219->dai_clks_lookup[i] = NULL;
> > > +		}
> >
> > It seems to me that devm_* functions should have freed up everything when
> the
> > codec module was removed. I can only assume the codec isn't being removed
> in
> > your test hence devm is never freeing the clock resource and is why you're
> > getting -EEXIST. Is this the case and is your use-case expected behaviour? It's
> > not something that has been reported previously so am keen to understand
> > exactly what's happening here.
> >
> > >  	}
> > >  #endif
> > >
> 
> When the card was uninstalled with modprobe -r, the da7219 codec was not
> removed, only component da7219_remove() is invoked, do you suggest the
> component driver probe and remove has to happen with da7219_i2_driver probe
> and remove together? Thanks for the code review.

Well as far as I understand it the the devm_* allocated resources are tied to
the i2c dev. If I'm correct then unless that's removed then those resources
won't be freed. If this is a valid scenario then we would probably have to look
at avoiding all devm_ calls in the da7219_probe() code as they wouldn't be
released when doing what you are here.

Mark, what's your take on this? Am I missing something obvious?