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Commit 7910b4a1 authored by Jaroslav Kysela's avatar Jaroslav Kysela
Browse files

ALSA: pcm_native - fix runtime->boundary calculation 



The code in pcm_lib updating runtime->hw_ptr_interrupt expects
that runtime->boundary is divisible with runtime->period_size.
Thanks are going to Clemens Ladisch for the notice.

Fix the runtime->boundary calculation using buffer_size * period_size
as base and find a least common multiple for 32bit platforms when
the expression might overflow.

Signed-off-by: default avatarJaroslav Kysela <perex@perex.cz>
parent e7636925

sound/core/pcm_native.c

+36 −3
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ 
#include <linux/pm_qos_params.h>

#include <linux/uio.h>

#include <linux/dma-mapping.h>

#include <linux/math64.h>

#include <sound/core.h>

#include <sound/control.h>

#include <sound/info.h>
@@ -366,6 +367,38 @@ static int period_to_usecs(struct snd_pcm_runtime *runtime) 
	return usecs;

}



static int calc_boundary(struct snd_pcm_runtime *runtime)

{

	u_int64_t boundary;



	boundary = (u_int64_t)runtime->buffer_size *

		   (u_int64_t)runtime->period_size;

#if BITS_PER_LONG < 64

	/* try to find lowest common multiple for buffer and period */

	if (boundary > LONG_MAX - runtime->buffer_size) {

		u_int32_t remainder = -1;

		u_int32_t divident = runtime->buffer_size;

		u_int32_t divisor = runtime->period_size;

		while (remainder) {

			remainder = divident % divisor;

			if (remainder) {

				divident = divisor;

				divisor = remainder;

			}

		}

		boundary = div_u64(boundary, divisor);

		if (boundary > LONG_MAX - runtime->buffer_size)

			return -ERANGE;

	}

#endif

	if (boundary == 0)

		return -ERANGE;

	runtime->boundary = boundary;

	while (runtime->boundary * 2 <= LONG_MAX - runtime->buffer_size)

		runtime->boundary *= 2;

	return 0;

}



static int snd_pcm_hw_params(struct snd_pcm_substream *substream,

			     struct snd_pcm_hw_params *params)

{
@@ -441,9 +474,9 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream, 
	runtime->stop_threshold = runtime->buffer_size;

	runtime->silence_threshold = 0;

	runtime->silence_size = 0;

	runtime->boundary = runtime->buffer_size;

	while (runtime->boundary * 2 <= LONG_MAX - runtime->buffer_size)

		runtime->boundary *= 2;

	err = calc_boundary(runtime);

	if (err < 0)

		goto _error;



	snd_pcm_timer_resolution_change(substream);

	runtime->status->state = SNDRV_PCM_STATE_SETUP;