ALSA: pcm: oss: Place the plugin buffer overflow checks correctly

The checks of the plugin buffer overflow in the previous fix by commit
  f2ecf90 ("ALSA: pcm: oss: Avoid plugin buffer overflow")
are put in the wrong places mistakenly, which leads to the expected
(repeated) sound when the rate plugin is involved.  Fix in the right
places.

Also, at those right places, the zero check is needed for the
termination node, so added there as well, and let's get it done,
finally.

Fixes: f2ecf90 ("ALSA: pcm: oss: Avoid plugin buffer overflow")
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200424193350.19678-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/oss/pcm_plugin.c

@@ -211,21 +211,23 @@ static snd_pcm_sframes_t plug_client_size(struct snd_pcm_substream *plug,
 	if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
 		plugin = snd_pcm_plug_last(plug);
 		while (plugin && drv_frames > 0) {
-			if (check_size && drv_frames > plugin->buf_frames)
-				drv_frames = plugin->buf_frames;
 			plugin_prev = plugin->prev;
 			if (plugin->src_frames)
 				drv_frames = plugin->src_frames(plugin, drv_frames);
+			if (check_size && plugin->buf_frames &&
+			    drv_frames > plugin->buf_frames)
+				drv_frames = plugin->buf_frames;
 			plugin = plugin_prev;
 		}
 	} else if (stream == SNDRV_PCM_STREAM_CAPTURE) {
 		plugin = snd_pcm_plug_first(plug);
 		while (plugin && drv_frames > 0) {
 			plugin_next = plugin->next;
+			if (check_size && plugin->buf_frames &&
+			    drv_frames > plugin->buf_frames)
+				drv_frames = plugin->buf_frames;
 			if (plugin->dst_frames)
 				drv_frames = plugin->dst_frames(plugin, drv_frames);
-			if (check_size && drv_frames > plugin->buf_frames)
-				drv_frames = plugin->buf_frames;
 			plugin = plugin_next;
 		}
 	} else
@@ -251,26 +253,28 @@ static snd_pcm_sframes_t plug_slave_size(struct snd_pcm_substream *plug,
 		plugin = snd_pcm_plug_first(plug);
 		while (plugin && frames > 0) {
 			plugin_next = plugin->next;
+			if (check_size && plugin->buf_frames &&
+			    frames > plugin->buf_frames)
+				frames = plugin->buf_frames;
 			if (plugin->dst_frames) {
 				frames = plugin->dst_frames(plugin, frames);
 				if (frames < 0)
 					return frames;
 			}
-			if (check_size && frames > plugin->buf_frames)
-				frames = plugin->buf_frames;
 			plugin = plugin_next;
 		}
 	} else if (stream == SNDRV_PCM_STREAM_CAPTURE) {
 		plugin = snd_pcm_plug_last(plug);
 		while (plugin) {
-			if (check_size && frames > plugin->buf_frames)
-				frames = plugin->buf_frames;
 			plugin_prev = plugin->prev;
 			if (plugin->src_frames) {
 				frames = plugin->src_frames(plugin, frames);
 				if (frames < 0)
 					return frames;
 			}
+			if (check_size && plugin->buf_frames &&
+			    frames > plugin->buf_frames)
+				frames = plugin->buf_frames;
 			plugin = plugin_prev;
 		}
 	} else