ALSA: oss: Use kvzalloc() for local buffer allocations

PCM OSS layer may allocate a few temporary buffers, one for the core
read/write and another for the conversions via plugins.  Currently
both are allocated via vmalloc().  But as the allocation size is
equivalent with the PCM period size, the required size might be quite
small, depending on the application.

This patch replaces these vmalloc() calls with kvzalloc() for covering
small period sizes better.  Also, we use "z"-alloc variant here for
addressing the possible uninitialized access reported by syzkaller.

Reported-by: syzbot+1cb36954e127c98dd037@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/oss/pcm_oss.c

@@ -1062,8 +1062,8 @@ static int snd_pcm_oss_change_params_locked(struct snd_pcm_substream *substream)
 	runtime->oss.channels = params_channels(params);
 	runtime->oss.rate = params_rate(params);
 
-	vfree(runtime->oss.buffer);
-	runtime->oss.buffer = vmalloc(runtime->oss.period_bytes);
+	kvfree(runtime->oss.buffer);
+	runtime->oss.buffer = kvzalloc(runtime->oss.period_bytes, GFP_KERNEL);
 	if (!runtime->oss.buffer) {
 		err = -ENOMEM;
 		goto failure;
@@ -2328,7 +2328,7 @@ static void snd_pcm_oss_release_substream(struct snd_pcm_substream *substream)
 {
 	struct snd_pcm_runtime *runtime;
 	runtime = substream->runtime;
-	vfree(runtime->oss.buffer);
+	kvfree(runtime->oss.buffer);
 	runtime->oss.buffer = NULL;
 #ifdef CONFIG_SND_PCM_OSS_PLUGINS
 	snd_pcm_oss_plugin_clear(substream);

sound/core/oss/pcm_plugin.c

@@ -66,8 +66,8 @@ static int snd_pcm_plugin_alloc(struct snd_pcm_plugin *plugin, snd_pcm_uframes_t
 		return -ENXIO;
 	size /= 8;
 	if (plugin->buf_frames < frames) {
-		vfree(plugin->buf);
-		plugin->buf = vmalloc(size);
+		kvfree(plugin->buf);
+		plugin->buf = kvzalloc(size, GFP_KERNEL);
 		plugin->buf_frames = frames;
 	}
 	if (!plugin->buf) {
@@ -191,7 +191,7 @@ int snd_pcm_plugin_free(struct snd_pcm_plugin *plugin)
 	if (plugin->private_free)
 		plugin->private_free(plugin);
 	kfree(plugin->buf_channels);
-	vfree(plugin->buf);
+	kvfree(plugin->buf);
 	kfree(plugin);
 	return 0;
 }