[PATCH 5.10.y] dmaengine: stm32: dmamux: fix device leak on route allocation

[Sasha Levin <sashal@kernel.org>]

From: Johan Hovold <johan@kernel.org>

[ Upstream commit dd6e4943889fb354efa3f700e42739da9bddb6ef ]

Make sure to drop the reference taken when looking up the DMA mux
platform device during route allocation.

Note that holding a reference to a device does not prevent its driver
data from going away so there is no point in keeping the reference.

Fixes: df7e762db5f6 ("dmaengine: Add STM32 DMAMUX driver")
Cc: stable@vger.kernel.org	# 4.15
Cc: Pierre-Yves MORDRET <pierre-yves.mordret@foss.st.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://patch.msgid.link/20251117161258.10679-11-johan@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/dma/stm32-dmamux.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/dma/stm32-dmamux.c b/drivers/dma/stm32-dmamux.c
index f04bcffd3c24a..07eb732ce50e1 100644
--- a/drivers/dma/stm32-dmamux.c
+++ b/drivers/dma/stm32-dmamux.c
@@ -88,23 +88,25 @@ static void *stm32_dmamux_route_allocate(struct of_phandle_args *dma_spec,
 	struct stm32_dmamux_data *dmamux = platform_get_drvdata(pdev);
 	struct stm32_dmamux *mux;
 	u32 i, min, max;
-	int ret;
+	int ret = -EINVAL;
 	unsigned long flags;
 
 	if (dma_spec->args_count != 3) {
 		dev_err(&pdev->dev, "invalid number of dma mux args\n");
-		return ERR_PTR(-EINVAL);
+		goto err_put_pdev;
 	}
 
 	if (dma_spec->args[0] > dmamux->dmamux_requests) {
 		dev_err(&pdev->dev, "invalid mux request number: %d\n",
 			dma_spec->args[0]);
-		return ERR_PTR(-EINVAL);
+		goto err_put_pdev;
 	}
 
 	mux = kzalloc(sizeof(*mux), GFP_KERNEL);
-	if (!mux)
-		return ERR_PTR(-ENOMEM);
+	if (!mux) {
+		ret = -ENOMEM;
+		goto err_put_pdev;
+	}
 
 	spin_lock_irqsave(&dmamux->lock, flags);
 	mux->chan_id = find_first_zero_bit(dmamux->dma_inuse,
@@ -131,7 +133,6 @@ static void *stm32_dmamux_route_allocate(struct of_phandle_args *dma_spec,
 	dma_spec->np = of_parse_phandle(ofdma->of_node, "dma-masters", i - 1);
 	if (!dma_spec->np) {
 		dev_err(&pdev->dev, "can't get dma master\n");
-		ret = -EINVAL;
 		goto error;
 	}
 
@@ -158,6 +159,8 @@ static void *stm32_dmamux_route_allocate(struct of_phandle_args *dma_spec,
 	dev_dbg(&pdev->dev, "Mapping DMAMUX(%u) to DMA%u(%u)\n",
 		mux->request, mux->master, mux->chan_id);
 
+	put_device(&pdev->dev);
+
 	return mux;
 
 error:
@@ -165,6 +168,9 @@ static void *stm32_dmamux_route_allocate(struct of_phandle_args *dma_spec,
 
 error_chan_id:
 	kfree(mux);
+err_put_pdev:
+	put_device(&pdev->dev);
+
 	return ERR_PTR(ret);
 }
 
-- 
2.51.0