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Message-ID: <s5h37x5g56w.wl-tiwai@suse.de> Date: Tue, 20 Oct 2015 13:17:11 +0200 From: Takashi Iwai <tiwai@...e.de> To: "Lars-Peter Clausen" <lars@...afoo.de> Cc: "Vinod Koul" <vinod.koul@...el.com>, <alsa-devel@...a-project.org>, "Russell King" <rmk+kernel@....linux.org.uk>, "Shengjiu Wang" <shengjiu.wang@...escale.com>, "Laurent Pinchart" <renesas@...asonboard.com>, "Dan Williams" <dan.j.williams@...el.com>, "Jonah Petri" <jpetri@...tope.com>, "Matt Campbell" <mcampbell@...tope.com>, "Qiao Zhou" <zhouqiao@...vell.com>, "Kuninori Morimoto" <kuninori.morimoto.gx@...esas.com>, <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 4/4] ALSA: pcm_dmaengine: Properly synchronize DMA on shutdown On Tue, 20 Oct 2015 11:46:31 +0200, Lars-Peter Clausen wrote: > > 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. What if a substream is restarted immediately after the stop? Takashi > > Signed-off-by: Lars-Peter Clausen <lars@...afoo.de> > --- > sound/core/pcm_dmaengine.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c > index fba365a..697c166 100644 > --- 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); > > -- > 2.1.4 > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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