audio/alsa-plugins: Fix two bugs in ALSA OSS backend.

When computing the oss_pointer() return value, use the application
pointer value as reference, so that ALSA audio applications at any
time don't read/write more audio data than is possible. Following the
cyclic DMA pointer is not a good idea, because it doesn't account for
under- or overruns and this quickly leads to a situation where some
applications may want to write more data, ending in infinite loops.

The SNDCTL_DSP_GET space ioctls operate on buffer fragments. Any
size less than bi.fragsize is reported as zero bytes. Don't set the
water level less than bi.fragsize, because it leads to infinite
polling the way ALSA PCM is working.

Approved by: pi (implicit)

2 files changed, 26 insertions, 37 deletions

diff --git a/audio/alsa-plugins/Makefile b/audio/alsa-plugins/Makefile
index e8a7d1eec77e..8b38f3b0bf13 100644
--- a/audio/alsa-plugins/Makefile
+++ b/audio/alsa-plugins/Makefile
@@ -2,7 +2,7 @@
 
 PORTNAME=	alsa-plugins
 PORTVERSION=	1.2.2
-PORTREVISION=	5
+PORTREVISION=	6
 DISTVERSIONPREFIX=	v
 CATEGORIES=	audio
 MASTER_SITES=	GH
diff --git a/audio/alsa-plugins/files/patch-oss_pcm__oss.c b/audio/alsa-plugins/files/patch-oss_pcm__oss.c
index 5b2e048e45b1..ca325bb68905 100644
--- a/audio/alsa-plugins/files/patch-oss_pcm__oss.c
+++ b/audio/alsa-plugins/files/patch-oss_pcm__oss.c
@@ -1,6 +1,6 @@
 --- oss/pcm_oss.c.orig	2020-02-19 09:35:42 UTC
 +++ oss/pcm_oss.c
-@@ -19,21 +19,45 @@
+@@ -19,21 +19,42 @@
   */
  
  #include <stdio.h>
@@ -39,19 +39,16 @@
 -	int fragment_set;
 -	int caps;
 +	int bufsz;
-+	int ptr;
-+	int ptr_align;
  	int format;
 -	unsigned int period_shift;
 -	unsigned int periods;
 -	unsigned int frame_bytes;
 +	int frame_bytes;
-+	int last_bytes;
 +	bool buffer_used;
  } snd_pcm_oss_t;
  
  static snd_pcm_sframes_t oss_write(snd_pcm_ioplug_t *io,
-@@ -49,8 +73,21 @@ static snd_pcm_sframes_t oss_write(snd_pcm_ioplug_t *i
+@@ -49,8 +70,21 @@ static snd_pcm_sframes_t oss_write(snd_pcm_ioplug_t *i
  	buf = (char *)areas->addr + (areas->first + areas->step * offset) / 8;
  	size *= oss->frame_bytes;
  	result = write(oss->fd, buf, size);
@@ -75,7 +72,7 @@
  	return result / oss->frame_bytes;
  }
  
-@@ -67,24 +104,66 @@ static snd_pcm_sframes_t oss_read(snd_pcm_ioplug_t *io
+@@ -67,24 +101,60 @@ static snd_pcm_sframes_t oss_read(snd_pcm_ioplug_t *io
  	buf = (char *)areas->addr + (areas->first + areas->step * offset) / 8;
  	size *= oss->frame_bytes;
  	result = read(oss->fd, buf, size);
@@ -104,21 +101,17 @@
  	snd_pcm_oss_t *oss = io->private_data;
 -	struct count_info info;
 -	int ptr;
-+	struct count_info ci;
 +	audio_buf_info bi;
++	ssize_t bytes;
  
 -	if (ioctl(oss->fd, io->stream == SND_PCM_STREAM_PLAYBACK ?
 -		  SNDCTL_DSP_GETOPTR : SNDCTL_DSP_GETIPTR, &info) < 0) {
 -		fprintf(stderr, "*** OSS: oss_pointer error\n");
 -		return 0;
 +	if (io->stream == SND_PCM_STREAM_PLAYBACK) {
-+		if (ioctl(oss->fd, SNDCTL_DSP_GETOPTR, &ci) < 0)
-+			return -EINVAL;
 +		if (ioctl(oss->fd, SNDCTL_DSP_GETOSPACE, &bi) < 0)
 +			return -EINVAL;
 +	} else {
-+		if (ioctl(oss->fd, SNDCTL_DSP_GETIPTR, &ci) < 0)
-+			return -EINVAL;
 +		if (ioctl(oss->fd, SNDCTL_DSP_GETISPACE, &bi) < 0)
 +			return -EINVAL;
  	}
@@ -136,23 +129,21 @@
 +		}
 +	}
 +
-+	if (oss->last_bytes == -1)
-+		oss->last_bytes = ci.ptr;
-+
-+	if (ci.ptr < oss->last_bytes)
-+		oss->ptr += oss->bufsz;
-+
-+	oss->ptr += ci.ptr;
-+	oss->ptr -= oss->last_bytes;
-+	oss->ptr %= oss->ptr_align;
++	if (io->stream == SND_PCM_STREAM_PLAYBACK)
++		bi.bytes = oss->bufsz - bi.bytes;
 +
-+	oss->last_bytes = ci.ptr;
++	/*
++	 * Return exactly how many bytes can be read or written,
++	 * relative to the current application pointer.
++	 */
++	bytes = snd_pcm_frames_to_bytes(io->pcm, io->appl_ptr) + bi.bytes;
++	bytes %= io->buffer_size * oss->frame_bytes;
 +
-+	return snd_pcm_bytes_to_frames(io->pcm, oss->ptr);
++	return snd_pcm_bytes_to_frames(io->pcm, bytes);
  }
  
  static int oss_start(snd_pcm_ioplug_t *io)
-@@ -93,12 +172,25 @@ static int oss_start(snd_pcm_ioplug_t *io)
+@@ -93,12 +163,23 @@ static int oss_start(snd_pcm_ioplug_t *io)
  	int tmp = io->stream == SND_PCM_STREAM_PLAYBACK ?
  		PCM_ENABLE_OUTPUT : PCM_ENABLE_INPUT;
  
@@ -171,14 +162,12 @@
 +#endif
  	}
 +
-+	oss->last_bytes = -1;
-+	oss->ptr = 0;
 +	oss->buffer_used = false;
 +
  	return 0;
  }
  
-@@ -107,6 +199,10 @@ static int oss_stop(snd_pcm_ioplug_t *io)
+@@ -107,6 +188,10 @@ static int oss_stop(snd_pcm_ioplug_t *io)
  	snd_pcm_oss_t *oss = io->private_data;
  	int tmp = 0;
  
@@ -189,7 +178,7 @@
  	ioctl(oss->fd, SNDCTL_DSP_SETTRIGGER, &tmp);
  	return 0;
  }
-@@ -115,101 +211,176 @@ static int oss_drain(snd_pcm_ioplug_t *io)
+@@ -115,101 +200,176 @@ static int oss_drain(snd_pcm_ioplug_t *io)
  {
  	snd_pcm_oss_t *oss = io->private_data;
  
@@ -301,7 +290,6 @@
 -		oss->format = AFMT_S16_BE;
 -		break;
 -	default:
-+	oss->ptr_align = io->buffer_size * oss->frame_bytes;
 +
 +	oss->format = 0;
 +	for (i = 0; i != ARRAY_SIZE(oss_formats_tab); i++) {
@@ -411,8 +399,9 @@
 +	tmp = io->period_size * oss->frame_bytes;
 +	if (tmp > oss->bufsz)
 +		tmp = oss->bufsz;
-+	else if (tmp == 0)
-+		tmp = 1;
++	else if (tmp < bi.fragsize)
++		tmp = bi.fragsize;
++
 +	if (ioctl(oss->fd, SNDCTL_DSP_LOW_WATER, &tmp) < 0)
 +		perror("SNDCTL_DSP_LOW_WATER");
 +#endif
@@ -431,7 +420,7 @@
  	if ((flags = fcntl(oss->fd, F_GETFL)) < 0) {
  		err = -errno;
  		perror("F_GETFL");
-@@ -229,16 +400,148 @@ static int oss_hw_params(snd_pcm_ioplug_t *io,
+@@ -229,16 +389,148 @@ static int oss_hw_params(snd_pcm_ioplug_t *io,
  	return 0;
  }
  
@@ -582,7 +571,7 @@
  	unsigned int format[5];
  	unsigned int nchannels;
  	unsigned int channel[6];
-@@ -317,6 +620,7 @@ static int oss_hw_constraint(snd_pcm_oss_t *oss)
+@@ -317,6 +609,7 @@ static int oss_hw_constraint(snd_pcm_oss_t *oss)
  		return err;
  
  	return 0;
@@ -590,7 +579,7 @@
  }
  
  
-@@ -324,6 +628,10 @@ static int oss_close(snd_pcm_ioplug_t *io)
+@@ -324,6 +617,10 @@ static int oss_close(snd_pcm_ioplug_t *io)
  {
  	snd_pcm_oss_t *oss = io->private_data;
  
@@ -601,7 +590,7 @@
  	close(oss->fd);
  	free(oss->device);
  	free(oss);
-@@ -337,8 +645,8 @@ static const snd_pcm_ioplug_callback_t oss_playback_ca
+@@ -337,8 +634,8 @@ static const snd_pcm_ioplug_callback_t oss_playback_ca
  	.pointer = oss_pointer,
  	.close = oss_close,
  	.hw_params = oss_hw_params,
@@ -611,7 +600,7 @@
  };
  
  static const snd_pcm_ioplug_callback_t oss_capture_callback = {
-@@ -348,8 +656,8 @@ static const snd_pcm_ioplug_callback_t oss_capture_cal
+@@ -348,8 +645,8 @@ static const snd_pcm_ioplug_callback_t oss_capture_cal
  	.pointer = oss_pointer,
  	.close = oss_close,
  	.hw_params = oss_hw_params,
@@ -621,7 +610,7 @@
  };
  
  
-@@ -360,6 +668,10 @@ SND_PCM_PLUGIN_DEFINE_FUNC(oss)
+@@ -360,6 +657,10 @@ SND_PCM_PLUGIN_DEFINE_FUNC(oss)
  	int err;
  	snd_pcm_oss_t *oss;