Commit 37a7ea4a authored Feb 06, 2017 by Takashi Iwai

ALSA: seq: Don't handle loop timeout at snd_seq_pool_done()

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

parent d5adbfcd

sound/core/seq/seq_memory.c

+1 −8

Original line number	Diff line number	Diff line
		@@ -419,7 +419,6 @@ 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;
		@@ -432,14 +431,8 @@ 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) {
		pr_warn("ALSA: 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);