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>

1 files changed, 2 insertions, 2 deletions

diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 9dd9bc73fe1d..ece25c718e95 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -781,7 +781,7 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
                 return -ENODEV;
 
         card = pcm->card;
-        down_read(&card->controls_rwsem);
+        read_lock(&card->ctl_files_rwlock);
         list_for_each_entry(kctl, &card->ctl_files, list) {
                 if (kctl->pid == current->pid) {
                         prefer_subdevice = kctl->prefer_pcm_subdevice;
@@ -789,7 +789,7 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
                                 break;
                 }
         }
-        up_read(&card->controls_rwsem);
+        read_unlock(&card->ctl_files_rwlock);
 
         switch (stream) {
         case SNDRV_PCM_STREAM_PLAYBACK: