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@xxxxxxxx> > Signed-off-by: Cezary Rojewski <cezary.rojewski@xxxxxxxxx> > --- > > 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@xxxxxxxxx/ Thanks, applied now. Takashi
