[PATCH 3/4] ASoC: stm32: sai: fix OF node leak on probe

[Johan Hovold <johan@kernel.org>]

The reference taken to the sync provider OF node when probing the
platform device is currently only dropped if the set_sync() callback
fails during DAI probe.

Make sure to drop the reference on platform probe failures (e.g. probe
deferral) and on driver unbind.

This also avoids a potential use-after-free in case the DAI is ever
reprobed without first rebinding the platform driver.

Fixes: 5914d285f6b7 ("ASoC: stm32: sai: Add synchronization support")
Fixes: d4180b4c02e7 ("ASoC: stm32: sai: fix set_sync service")
Cc: Olivier Moysan <olivier.moysan@st.com>
Cc: stable@vger.kernel.org      # 4.16: d4180b4c02e7
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 sound/soc/stm/stm32_sai.c     | 12 +++---------
 sound/soc/stm/stm32_sai_sub.c | 23 ++++++++++++++++-------
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/sound/soc/stm/stm32_sai.c b/sound/soc/stm/stm32_sai.c
index 7065aeb0e524..00cf24ceca2d 100644
--- a/sound/soc/stm/stm32_sai.c
+++ b/sound/soc/stm/stm32_sai.c
@@ -138,7 +138,6 @@ static int stm32_sai_set_sync(struct stm32_sai_data *sai_client,
 	if (!pdev) {
 		dev_err(&sai_client->pdev->dev,
 			"Device not found for node %pOFn\n", np_provider);
-		of_node_put(np_provider);
 		return -ENODEV;
 	}
 
@@ -147,21 +146,16 @@ static int stm32_sai_set_sync(struct stm32_sai_data *sai_client,
 	if (!sai_provider) {
 		dev_err(&sai_client->pdev->dev,
 			"SAI sync provider data not found\n");
-		ret = -EINVAL;
-		goto error;
+		return -EINVAL;
 	}
 
 	/* Configure sync client */
 	ret = stm32_sai_sync_conf_client(sai_client, synci);
 	if (ret < 0)
-		goto error;
+		return ret;
 
 	/* Configure sync provider */
-	ret = stm32_sai_sync_conf_provider(sai_provider, synco);
-
-error:
-	of_node_put(np_provider);
-	return ret;
+	return stm32_sai_sync_conf_provider(sai_provider, synco);
 }
 
 static int stm32_sai_get_parent_clk(struct stm32_sai_data *sai)
diff --git a/sound/soc/stm/stm32_sai_sub.c b/sound/soc/stm/stm32_sai_sub.c
index 7a005b4ad304..5ae4d2577f28 100644
--- a/sound/soc/stm/stm32_sai_sub.c
+++ b/sound/soc/stm/stm32_sai_sub.c
@@ -1586,7 +1586,8 @@ static int stm32_sai_sub_parse_of(struct platform_device *pdev,
 				dev_err(&pdev->dev,
 					"External synchro not supported\n");
 				of_node_put(args.np);
-				return -EINVAL;
+				ret = -EINVAL;
+				goto err_put_sync_provider;
 			}
 			sai->sync = SAI_SYNC_EXTERNAL;
 
@@ -1595,7 +1596,8 @@ static int stm32_sai_sub_parse_of(struct platform_device *pdev,
 			    (sai->synci > (SAI_GCR_SYNCIN_MAX + 1))) {
 				dev_err(&pdev->dev, "Wrong SAI index\n");
 				of_node_put(args.np);
-				return -EINVAL;
+				ret = -EINVAL;
+				goto err_put_sync_provider;
 			}
 
 			if (of_property_match_string(args.np, "compatible",
@@ -1609,7 +1611,8 @@ static int stm32_sai_sub_parse_of(struct platform_device *pdev,
 			if (!sai->synco) {
 				dev_err(&pdev->dev, "Unknown SAI sub-block\n");
 				of_node_put(args.np);
-				return -EINVAL;
+				ret = -EINVAL;
+				goto err_put_sync_provider;
 			}
 		}
 
@@ -1619,13 +1622,15 @@ static int stm32_sai_sub_parse_of(struct platform_device *pdev,
 
 	of_node_put(args.np);
 	sai->sai_ck = devm_clk_get(&pdev->dev, "sai_ck");
-	if (IS_ERR(sai->sai_ck))
-		return dev_err_probe(&pdev->dev, PTR_ERR(sai->sai_ck),
-				     "Missing kernel clock sai_ck\n");
+	if (IS_ERR(sai->sai_ck)) {
+		ret = dev_err_probe(&pdev->dev, PTR_ERR(sai->sai_ck),
+				    "Missing kernel clock sai_ck\n");
+		goto err_put_sync_provider;
+	}
 
 	ret = clk_prepare(sai->pdata->pclk);
 	if (ret < 0)
-		return ret;
+		goto err_put_sync_provider;
 
 	if (STM_SAI_IS_F4(sai->pdata))
 		return 0;
@@ -1647,6 +1652,8 @@ static int stm32_sai_sub_parse_of(struct platform_device *pdev,
 
 err_unprepare_pclk:
 	clk_unprepare(sai->pdata->pclk);
+err_put_sync_provider:
+	of_node_put(sai->np_sync_provider);
 
 	return ret;
 }
@@ -1720,6 +1727,7 @@ static int stm32_sai_sub_probe(struct platform_device *pdev)
 
 err_unprepare_pclk:
 	clk_unprepare(sai->pdata->pclk);
+	of_node_put(sai->np_sync_provider);
 
 	return ret;
 }
@@ -1732,6 +1740,7 @@ static void stm32_sai_sub_remove(struct platform_device *pdev)
 	snd_dmaengine_pcm_unregister(&pdev->dev);
 	snd_soc_unregister_component(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
+	of_node_put(sai->np_sync_provider);
 }
 
 static int stm32_sai_sub_suspend(struct device *dev)
-- 
2.51.2