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    Subject[PATCH AUTOSEL 5.19 38/48] ALSA: pcm: Use deferred fasync helper
    Date
    From: Takashi Iwai <tiwai@suse.de>

    [ Upstream commit 96b097091c66df4f6fbf5cbff21df6cc02a2f055 ]

    For avoiding the potential deadlock via kill_fasync() call, use the
    new fasync helpers to defer the invocation from timer API. Note that
    it's merely a workaround.

    Reported-by: syzbot+8285e973a41b5aa68902@syzkaller.appspotmail.com
    Reported-by: syzbot+669c9abf11a6a011dd09@syzkaller.appspotmail.com
    Link: https://lore.kernel.org/r/20220728125945.29533-4-tiwai@suse.de
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    include/sound/pcm.h | 2 +-
    sound/core/pcm.c | 1 +
    sound/core/pcm_lib.c | 2 +-
    sound/core/pcm_native.c | 2 +-
    4 files changed, 4 insertions(+), 3 deletions(-)

    diff --git a/include/sound/pcm.h b/include/sound/pcm.h
    index 6b99310b5b88..6987110843f0 100644
    --- a/include/sound/pcm.h
    +++ b/include/sound/pcm.h
    @@ -399,7 +399,7 @@ struct snd_pcm_runtime {
    snd_pcm_uframes_t twake; /* do transfer (!poll) wakeup if non-zero */
    wait_queue_head_t sleep; /* poll sleep */
    wait_queue_head_t tsleep; /* transfer sleep */
    - struct fasync_struct *fasync;
    + struct snd_fasync *fasync;
    bool stop_operating; /* sync_stop will be called */
    struct mutex buffer_mutex; /* protect for buffer changes */
    atomic_t buffer_accessing; /* >0: in r/w operation, <0: blocked */
    diff --git a/sound/core/pcm.c b/sound/core/pcm.c
    index 977d54320a5c..c917ac84a7e5 100644
    --- a/sound/core/pcm.c
    +++ b/sound/core/pcm.c
    @@ -1005,6 +1005,7 @@ void snd_pcm_detach_substream(struct snd_pcm_substream *substream)
    substream->runtime = NULL;
    }
    mutex_destroy(&runtime->buffer_mutex);
    + snd_fasync_free(runtime->fasync);
    kfree(runtime);
    put_pid(substream->pid);
    substream->pid = NULL;
    diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
    index 1fc7c50ffa62..40751e5aff09 100644
    --- a/sound/core/pcm_lib.c
    +++ b/sound/core/pcm_lib.c
    @@ -1822,7 +1822,7 @@ void snd_pcm_period_elapsed_under_stream_lock(struct snd_pcm_substream *substrea
    snd_timer_interrupt(substream->timer, 1);
    #endif
    _end:
    - kill_fasync(&runtime->fasync, SIGIO, POLL_IN);
    + snd_kill_fasync(runtime->fasync, SIGIO, POLL_IN);
    }
    EXPORT_SYMBOL(snd_pcm_period_elapsed_under_stream_lock);

    diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
    index 4adaee62ef33..16fcf57c6f03 100644
    --- a/sound/core/pcm_native.c
    +++ b/sound/core/pcm_native.c
    @@ -3945,7 +3945,7 @@ static int snd_pcm_fasync(int fd, struct file * file, int on)
    runtime = substream->runtime;
    if (runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
    return -EBADFD;
    - return fasync_helper(fd, file, on, &runtime->fasync);
    + return snd_fasync_helper(fd, file, on, &runtime->fasync);
    }

    /*
    --
    2.35.1
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