linux-kernel - [PATCH 4.9 27/28] ASoC: Intel: avoid Oops if DMA setup fails

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Date:   Thu,  9 May 2019 20:42:19 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ross Zwisler <zwisler@...gle.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>
Subject: [PATCH 4.9 27/28] ASoC: Intel: avoid Oops if DMA setup fails

From: Ross Zwisler <zwisler@...omium.org>

commit 0efa3334d65b7f421ba12382dfa58f6ff5bf83c4 upstream.

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@...gle.com>
Cc: stable@...r.kernel.org
Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 sound/soc/intel/common/sst-firmware.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/sound/soc/intel/common/sst-firmware.c
+++ b/sound/soc/intel/common/sst-firmware.c
@@ -1252,11 +1252,15 @@ struct sst_dsp *sst_dsp_new(struct devic
 		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);