From: Takashi Iwai <tiwai@xxxxxxx> commit 3c3201f8c7bb77eb53b08a3ca8d9a4ddc500b4c0 upstream. Like the previous fixes to hw_params and hw_free ioctl races, we need to paper over the concurrent prepare ioctl calls against hw_params and hw_free, too. This patch implements the locking with the existing runtime->buffer_mutex for prepare ioctls. Unlike the previous case for snd_pcm_hw_hw_params() and snd_pcm_hw_free(), snd_pcm_prepare() is performed to the linked streams, hence the lock can't be applied simply on the top. For tracking the lock in each linked substream, we modify snd_pcm_action_group() slightly and apply the buffer_mutex for the case stream_lock=false (formerly there was no lock applied) there. Cc: <stable@xxxxxxxxxxxxxxx> Reviewed-by: Jaroslav Kysela <perex@xxxxxxxx> Link: https://lore.kernel.org/r/20220322170720.3529-4-tiwai@xxxxxxx Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> [OP: backport to 4.14: adjusted context] Signed-off-by: Ovidiu Panait <ovidiu.panait@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- sound/core/pcm_native.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-) --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -1046,15 +1046,17 @@ struct action_ops { */ static int snd_pcm_action_group(const struct action_ops *ops, struct snd_pcm_substream *substream, - int state, int do_lock) + int state, int stream_lock) { struct snd_pcm_substream *s = NULL; struct snd_pcm_substream *s1; int res = 0, depth = 1; snd_pcm_group_for_each_entry(s, substream) { - if (do_lock && s != substream) { - if (s->pcm->nonatomic) + if (s != substream) { + if (!stream_lock) + mutex_lock_nested(&s->runtime->buffer_mutex, depth); + else if (s->pcm->nonatomic) mutex_lock_nested(&s->self_group.mutex, depth); else spin_lock_nested(&s->self_group.lock, depth); @@ -1082,18 +1084,18 @@ static int snd_pcm_action_group(const st ops->post_action(s, state); } _unlock: - if (do_lock) { - /* unlock streams */ - snd_pcm_group_for_each_entry(s1, substream) { - if (s1 != substream) { - if (s1->pcm->nonatomic) - mutex_unlock(&s1->self_group.mutex); - else - spin_unlock(&s1->self_group.lock); - } - if (s1 == s) /* end */ - break; + /* unlock streams */ + snd_pcm_group_for_each_entry(s1, substream) { + if (s1 != substream) { + if (!stream_lock) + mutex_unlock(&s1->runtime->buffer_mutex); + else if (s1->pcm->nonatomic) + mutex_unlock(&s1->self_group.mutex); + else + spin_unlock(&s1->self_group.lock); } + if (s1 == s) /* end */ + break; } return res; } @@ -1174,10 +1176,12 @@ static int snd_pcm_action_nonatomic(cons int res; down_read(&snd_pcm_link_rwsem); + mutex_lock(&substream->runtime->buffer_mutex); if (snd_pcm_stream_linked(substream)) res = snd_pcm_action_group(ops, substream, state, 0); else res = snd_pcm_action_single(ops, substream, state); + mutex_unlock(&substream->runtime->buffer_mutex); up_read(&snd_pcm_link_rwsem); return res; }
