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Subject[patch 15/71] ALSA: fix locking in snd_pcm_open*() and snd_rawmidi_open*()
2.6.26-stable review patch.  If anyone has any objections, please let us
know.

------------------
From: Takashi Iwai <tiwai@suse.de>
Upstream-commit-id: 399ccdc1cd4e92e541d4dacbbf18c52bd693418b

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
sound/core/pcm.c | 4 ++--
sound/core/rawmidi.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -781,7 +781,7 @@ int snd_pcm_attach_substream(struct snd_
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_
break;
}
}
- up_read(&card->controls_rwsem);
+ read_unlock(&card->ctl_files_rwlock);

switch (stream) {
case SNDRV_PCM_STREAM_PLAYBACK:
--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -418,7 +418,7 @@ static int snd_rawmidi_open(struct inode
mutex_lock(&rmidi->open_mutex);
while (1) {
subdevice = -1;
- 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) {
subdevice = kctl->prefer_rawmidi_subdevice;
@@ -426,7 +426,7 @@ static int snd_rawmidi_open(struct inode
break;
}
}
- up_read(&card->controls_rwsem);
+ read_unlock(&card->ctl_files_rwlock);
err = snd_rawmidi_kernel_open(rmidi->card, rmidi->device,
subdevice, fflags, rawmidi_file);
if (err >= 0)
--


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