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    Subject[PATCH 3.10 037/268] ALSA: seq: Don't handle loop timeout at snd_seq_pool_done()
    Date
    From: Takashi Iwai <tiwai@suse.de>

    commit 37a7ea4a9b81f6a864c10a7cb0b96458df5310a3 upstream.

    snd_seq_pool_done() syncs with closing of all opened threads, but it
    aborts the wait loop with a timeout, and proceeds to the release
    resource even if not all threads have been closed. The timeout was 5
    seconds, and if you run a crazy stuff, it can exceed easily, and may
    result in the access of the invalid memory address -- this is what
    syzkaller detected in a bug report.

    As a fix, let the code graduate from naiveness, simply remove the loop
    timeout.

    BugLink: http://lkml.kernel.org/r/CACT4Y+YdhDV2H5LLzDTJDVF-qiYHUHhtRaW4rbb4gUhTCQB81w@mail.gmail.com
    Reported-by: Dmitry Vyukov <dvyukov@google.com>
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Willy Tarreau <w@1wt.eu>
    ---
    sound/core/seq/seq_memory.c | 9 +--------
    1 file changed, 1 insertion(+), 8 deletions(-)

    diff --git a/sound/core/seq/seq_memory.c b/sound/core/seq/seq_memory.c
    index f478f77..fbe8d94 100644
    --- a/sound/core/seq/seq_memory.c
    +++ b/sound/core/seq/seq_memory.c
    @@ -416,7 +416,6 @@ int snd_seq_pool_done(struct snd_seq_pool *pool)
    {
    unsigned long flags;
    struct snd_seq_event_cell *ptr;
    - int max_count = 5 * HZ;

    if (snd_BUG_ON(!pool))
    return -EINVAL;
    @@ -429,14 +428,8 @@ int snd_seq_pool_done(struct snd_seq_pool *pool)
    if (waitqueue_active(&pool->output_sleep))
    wake_up(&pool->output_sleep);

    - while (atomic_read(&pool->counter) > 0) {
    - if (max_count == 0) {
    - snd_printk(KERN_WARNING "snd_seq_pool_done timeout: %d cells remain\n", atomic_read(&pool->counter));
    - break;
    - }
    + while (atomic_read(&pool->counter) > 0)
    schedule_timeout_uninterruptible(1);
    - max_count--;
    - }

    /* release all resources */
    spin_lock_irqsave(&pool->lock, flags);
    --
    2.8.0.rc2.1.gbe9624a
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