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SubjectRe: [PATCH v2] ASoC: Intel: avoid Oops if DMA setup fails
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On 4/29/19 1:25 PM, Ross Zwisler wrote:
> Currently in sst_dsp_new() if we get an error return from sst_dma_new()
> we just print an error message and then still complete the function
> successfully. This means that we are trying to run without sst->dma
> properly set up, which will result in NULL pointer dereference when
> sst->dma is later used. This was happening for me in
> sst_dsp_dma_get_channel():
>
> struct sst_dma *dma = dsp->dma;
> ...
> dma->ch = dma_request_channel(mask, dma_chan_filter, dsp);
>
> This resulted in:
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
> IP: sst_dsp_dma_get_channel+0x4f/0x125 [snd_soc_sst_firmware]
>
> Fix this by adding proper error handling for the case where we fail to
> set up DMA.
>
> This change only affects Haswell and Broadwell systems. Baytrail
> systems explicilty opt-out of DMA via sst->pdata->resindex_dma_base
> being set to -1.
>
> Signed-off-by: Ross Zwisler <zwisler@google.com>
> Cc: stable@vger.kernel.org

Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>

Thanks Ross!

FWIW we should start deprecating this driver now and transition to SOF.
I'll double-check how the upcoming 1.3 release works on my Pixel
2015/Samus device later this week.


> ---
>
> Changes in v2:
> - Upgraded the sst_dma_new() failure message from dev_warn() to dev_err()
> (Pierre-Louis).
> - Noted in the changelog that this change only affects Haswell and
> Broadwell (Pierre-Louis).
>
> ---
> sound/soc/intel/common/sst-firmware.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/sound/soc/intel/common/sst-firmware.c b/sound/soc/intel/common/sst-firmware.c
> index 1e067504b6043..f830e59f93eaa 100644
> --- a/sound/soc/intel/common/sst-firmware.c
> +++ b/sound/soc/intel/common/sst-firmware.c
> @@ -1251,11 +1251,15 @@ struct sst_dsp *sst_dsp_new(struct device *dev,
> goto irq_err;
>
> err = sst_dma_new(sst);
> - if (err)
> - dev_warn(dev, "sst_dma_new failed %d\n", err);
> + if (err) {
> + dev_err(dev, "sst_dma_new failed %d\n", err);
> + goto dma_err;
> + }
>
> return sst;
>
> +dma_err:
> + free_irq(sst->irq, sst);
> irq_err:
> if (sst->ops->free)
> sst->ops->free(sst);
>

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