Re: [PATCH v2] ALSA: hda: Do not unset preset when cleaning up codec

[Takashi Iwai <tiwai@suse.de>]

On Thu, 19 Jan 2023 15:32:35 +0100,
Cezary Rojewski wrote:
> 
> Several functions that take part in codec's initialization and removal
> are re-used by ASoC codec drivers implementations. Drivers mimic the
> behavior of hda_codec_driver_probe/remove() found in
> sound/pci/hda/hda_bind.c with their component->probe/remove() instead.
> 
> One of the reasons for that is the expectation of
> snd_hda_codec_device_new() to receive a valid pointer to an instance of
> struct snd_card. This expectation can be met only once sound card
> components probing commences.
> 
> As ASoC sound card may be unbound without codec device being actually
> removed from the system, unsetting ->preset in
> snd_hda_codec_cleanup_for_unbind() interferes with module unload -> load
> scenario causing null-ptr-deref. Preset is assigned only once, during
> device/driver matching whereas ASoC codec driver's module reloading may
> occur several times throughout the lifetime of an audio stack.
> 
> Suggested-by: Takashi Iwai <tiwai@suse.com>
> Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
> ---
> 
> Changes in v2:
> - relocated the operation to routines found in hda_bind.c rather than
>   just removing it from the cleanup function
> 
> 
> This is a continuation of a discussion that begun in the middle of 2022
> [1] and was part of a larger series addressing several HDAudio topics.
> 
> Single rmmod on ASoC's codec driver module is enough to cause a panic.
> Given our results, no regression shows up with modprobe/rmmod on
> snd_hda_intel side with this patch applied.
> 
> [1]: https://lore.kernel.org/alsa-devel/20220706120230.427296-2-cezary.rojewski@intel.com/

Thanks, applied now.


Takashi