ALSA: fix locking in snd_pcm_open*() and snd_rawmidi_open*()
authorTakashi Iwai <tiwai@suse.de>
Thu, 25 Sep 2008 12:51:03 +0000 (14:51 +0200)
committerTakashi Iwai <tiwai@suse.de>
Thu, 25 Sep 2008 12:51:03 +0000 (14:51 +0200)
commit399ccdc1cd4e92e541d4dacbbf18c52bd693418b
tree4e9ecc896adb79397166c02bdd4cedd690a54a98
parentb0b8daf7849cc98217ca018fbe82c61cd2b735bc
ALSA: fix locking in snd_pcm_open*() and snd_rawmidi_open*()

The PCM and rawmidi open callbacks have a lock against card->controls_list
but it takes a wrong one, card->controls_rwsem, instead of a right one
card->ctl_files_rwlock.  This patch fixes them.

This change also fixes automatically the potential deadlocks due to
mm->mmap_sem in munmap and copy_from/to_user, reported by Sitsofe
Wheeler:

  A: snd_ctl_elem_user_tlv(): card->controls_rwsem => mm->mmap_sem
  B: snd_pcm_open(): card->open_mutex => card->controls_rwsem
  C: munmap: mm->mmap_sem => snd_pcm_release(): card->open_mutex

The patch breaks the chain.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
sound/core/pcm.c
sound/core/rawmidi.c