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    Subject[PATCH 3.2 31/67] ALSA: seq: Fix race at closing in virmidi driver
    3.2.78-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Takashi Iwai <tiwai@suse.de>

    commit 2d1b5c08366acd46c35a2e9aba5d650cb5bf5c19 upstream.

    The virmidi driver has an open race at closing its assigned rawmidi
    device, and this may lead to use-after-free in
    snd_seq_deliver_single_event().

    Plug the hole by properly protecting the linked list deletion and
    calling in the right order in snd_virmidi_input_close().

    BugLink: http://lkml.kernel.org/r/CACT4Y+Zd66+w12fNN85-425cVQT=K23kWbhnCEcMB8s3us-Frw@mail.gmail.com
    Reported-by: Dmitry Vyukov <dvyukov@google.com>
    Tested-by: Dmitry Vyukov <dvyukov@google.com>
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    sound/core/seq/seq_virmidi.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    --- a/sound/core/seq/seq_virmidi.c
    +++ b/sound/core/seq/seq_virmidi.c
    @@ -254,9 +254,13 @@ static int snd_virmidi_output_open(struc
    */
    static int snd_virmidi_input_close(struct snd_rawmidi_substream *substream)
    {
    + struct snd_virmidi_dev *rdev = substream->rmidi->private_data;
    struct snd_virmidi *vmidi = substream->runtime->private_data;
    - snd_midi_event_free(vmidi->parser);
    +
    + write_lock_irq(&rdev->filelist_lock);
    list_del(&vmidi->list);
    + write_unlock_irq(&rdev->filelist_lock);
    + snd_midi_event_free(vmidi->parser);
    substream->runtime->private_data = NULL;
    kfree(vmidi);
    return 0;
    \
     
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