ALSA: jack: Pin the module while debugfs files are open

With CONFIG_SND=m and CONFIG_SND_JACK_INJECTION_DEBUG enabled, an in-tree
HDA jack creates these debugfs files through snd_jack_new() and
snd_jack_add_debugfs(). Their file_operations live in snd, but none sets
.owner. full_proxy_open_regular() therefore takes no snd module reference
when it calls fops_get(real_fops).

A debugfs descriptor can outlive removal of its HDA card. Once the card
and dependent modules, including the OSS emulation modules, have been
removed, snd can be unloaded while that descriptor is still open:

  Descriptor holder                   Card/module teardown
  -----------------                   --------------------
  open jack debugfs file
    full_proxy_open_regular()
      fops_get(real_fops)
        owner == NULL: no snd pin
  keep descriptor open
                                      remove HDA card
                                        snd_card_disconnect()
                                          snd_jack_dev_disconnect()
                                          remove debugfs nodes
                                        snd_jack_dev_free()
                                      unload dependent modules
                                      rmmod snd
                                        alsa_sound_exit()
                                        free_module(): unmap snd
  close descriptor
    full_proxy_release()
      read real_fops->release
      fops_put(real_fops)
        read real_fops->owner

debugfs_remove() drains active operations, but does not wait for idle
open descriptors. Release deliberately bypasses removal protection and
reads the real table even when no release callback is installed. The
last close can therefore access unloaded snd storage.

Set .owner to THIS_MODULE in all six tables. The existing proxy
fops_get()/fops_put() pair then keeps snd loaded through the final table
access on close.

Fixes: 2d670ea2bd53 ("ALSA: jack: implement software jack injection via debugfs")
Assisted-by: LLM
Signed-off-by: Cen Zhang <zzzccc427@gmail.com>
Link: https://patch.msgid.link/pm-pmb-431ddb947e1a13b95d3a-v3-02d37dd7b4eb4774e100@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

0 files changed, 0 insertions, 0 deletions