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    Subject[PATCH 3.13.y-ckt 29/43] ALSA: seq: oss: Don't drain at closing a client
    Date
    3.13.11-ckt37 -stable review patch.  If anyone has any objections, please let me know.

    ---8<------------------------------------------------------------

    From: Takashi Iwai <tiwai@suse.de>

    commit 197b958c1e76a575d77038cc98b4bebc2134279f upstream.

    The OSS sequencer client tries to drain the pending events at
    releasing. Unfortunately, as spotted by syzkaller fuzzer, this may
    lead to an unkillable process state when the event has been queued at
    the far future. Since the process being released can't be signaled
    any longer, it remains and waits for the echo-back event in that far
    future.

    Back to history, the draining feature was implemented at the time we
    misinterpreted POSIX definition for blocking file operation.
    Actually, such a behavior is superfluous at release, and we should
    just release the device as is instead of keeping it up forever.

    This patch just removes the draining call that may block the release
    for too long time unexpectedly.

    BugLink: http://lkml.kernel.org/r/CACT4Y+Y4kD-aBGj37rf-xBw9bH3GMU6P+MYg4W1e-s-paVD2pg@mail.gmail.com
    Reported-by: Dmitry Vyukov <dvyukov@google.com>
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    [ kamal: backport to 3.13-stable: context ]
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    sound/core/seq/oss/seq_oss.c | 2 --
    sound/core/seq/oss/seq_oss_device.h | 1 -
    sound/core/seq/oss/seq_oss_init.c | 17 -----------------
    3 files changed, 20 deletions(-)

    diff --git a/sound/core/seq/oss/seq_oss.c b/sound/core/seq/oss/seq_oss.c
    index 8d4d5e8..ab77495 100644
    --- a/sound/core/seq/oss/seq_oss.c
    +++ b/sound/core/seq/oss/seq_oss.c
    @@ -150,8 +150,6 @@ odev_release(struct inode *inode, struct file *file)
    if ((dp = file->private_data) == NULL)
    return 0;

    - snd_seq_oss_drain_write(dp);
    -
    mutex_lock(&register_mutex);
    snd_seq_oss_release(dp);
    mutex_unlock(&register_mutex);
    diff --git a/sound/core/seq/oss/seq_oss_device.h b/sound/core/seq/oss/seq_oss_device.h
    index c0154a9..2464112 100644
    --- a/sound/core/seq/oss/seq_oss_device.h
    +++ b/sound/core/seq/oss/seq_oss_device.h
    @@ -131,7 +131,6 @@ int snd_seq_oss_write(struct seq_oss_devinfo *dp, const char __user *buf, int co
    unsigned int snd_seq_oss_poll(struct seq_oss_devinfo *dp, struct file *file, poll_table * wait);

    void snd_seq_oss_reset(struct seq_oss_devinfo *dp);
    -void snd_seq_oss_drain_write(struct seq_oss_devinfo *dp);

    /* */
    void snd_seq_oss_process_queue(struct seq_oss_devinfo *dp, abstime_t time);
    diff --git a/sound/core/seq/oss/seq_oss_init.c b/sound/core/seq/oss/seq_oss_init.c
    index caa68d5..72b1df0 100644
    --- a/sound/core/seq/oss/seq_oss_init.c
    +++ b/sound/core/seq/oss/seq_oss_init.c
    @@ -457,23 +457,6 @@ snd_seq_oss_release(struct seq_oss_devinfo *dp)


    /*
    - * Wait until the queue is empty (if we don't have nonblock)
    - */
    -void
    -snd_seq_oss_drain_write(struct seq_oss_devinfo *dp)
    -{
    - if (! dp->timer->running)
    - return;
    - if (is_write_mode(dp->file_mode) && !is_nonblock_mode(dp->file_mode) &&
    - dp->writeq) {
    - debug_printk(("syncing..\n"));
    - while (snd_seq_oss_writeq_sync(dp->writeq))
    - ;
    - }
    -}
    -
    -
    -/*
    * reset sequencer devices
    */
    void
    --
    2.7.0
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