ALSA: snd-aloop - fix issue in the timer start function

In some circumstances (the rate shift value was changed), the irq_pos
value may be higher than the fraction value in the timer start function.
Check for it.

Also, to avoid value overflow, decrease maximum period size.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

1 files changed, 7 insertions, 1 deletions

diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
index 3c0088272095..838ad86311b8 100644
--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -171,6 +171,10 @@ static void loopback_timer_start(struct loopback_pcm *dpcm)
                 dpcm->pcm_rate_shift = rate_shift;
                 dpcm->period_size_frac = frac_pos(dpcm, dpcm->pcm_period_size);
         }
+        if (dpcm->period_size_frac <= dpcm->irq_pos) {
+                dpcm->irq_pos %= dpcm->period_size_frac;
+                dpcm->period_update_pending = 1;
+        }
         tick = dpcm->period_size_frac - dpcm->irq_pos;
         tick = (tick + dpcm->pcm_bps - 1) / dpcm->pcm_bps;
         dpcm->timer.expires = jiffies + tick;
@@ -531,7 +535,9 @@ static struct snd_pcm_hardware loopback_pcm_hardware =
         .channels_max =         32,
         .buffer_bytes_max =     2 * 1024 * 1024,
         .period_bytes_min =     64,
-        .period_bytes_max =     2 * 1024 * 1024,
+        /* note check overflow in frac_pos() using pcm_rate_shift before
+           changing period_bytes_max value */
+        .period_bytes_max =     1024 * 1024,
         .periods_min =          1,
         .periods_max =          1024,
         .fifo_size =            0,