ALSA: pcm_dmaengine: Properly synchronize DMA on shutdown

Use the new dmaengine_synchronize() function to make sure that all complete
callbacks have finished running before the runtime data, which is accessed
in the completed callback, is freed.

This fixes a long standing use-after-free race condition that has been
observed on some systems.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c
index fba365a..697c166 100644 (file)
--- a/sound/core/pcm_dmaengine.c
+++ b/sound/core/pcm_dmaengine.c
@@ -202,13 +202,13 @@ int snd_dmaengine_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
                if (runtime->info & SNDRV_PCM_INFO_PAUSE)
                        dmaengine_pause(prtd->dma_chan);
                else
-                       dmaengine_terminate_all(prtd->dma_chan);
+                       dmaengine_terminate_async(prtd->dma_chan);
                break;
        case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
                dmaengine_pause(prtd->dma_chan);
                break;
        case SNDRV_PCM_TRIGGER_STOP:
-               dmaengine_terminate_all(prtd->dma_chan);
+               dmaengine_terminate_async(prtd->dma_chan);
                break;
        default:
                return -EINVAL;
@@ -346,6 +346,7 @@ int snd_dmaengine_pcm_close(struct snd_pcm_substream *substream)
 {
        struct dmaengine_pcm_runtime_data *prtd = substream_to_prtd(substream);
 
+       dmaengine_synchronize(prtd->dma_chan);
        kfree(prtd);
 
        return 0;
@@ -362,9 +363,11 @@ int snd_dmaengine_pcm_close_release_chan(struct snd_pcm_substream *substream)
 {
        struct dmaengine_pcm_runtime_data *prtd = substream_to_prtd(substream);
 
+       dmaengine_synchronize(prtd->dma_chan);
        dma_release_channel(prtd->dma_chan);
+       kfree(prtd);
 
-       return snd_dmaengine_pcm_close(substream);
+       return 0;
 }
 EXPORT_SYMBOL_GPL(snd_dmaengine_pcm_close_release_chan);