[PATCH v2] mtd: rawnand: atmel: fix refcount issue in atmel_nand_controller_init

[Xin Xiong]

The reference counting issue happens in several error handling paths
on a refcounted object "nc->dmac". In these paths, the function simply
returns the error code, forgetting to balance the reference count of
"nc->dmac", increased earlier by dma_request_channel(), which may
cause refcount leaks.

Fix it by decrementing the refcount of specific object in those error
paths.

Fixes: f88fc122cc34 ("mtd: nand: Cleanup/rework the atmel_nand driver")
Co-developed-by: Xiyu Yang <xiyuyang19 at fudan.edu.cn>
Signed-off-by: Xiyu Yang <xiyuyang19 at fudan.edu.cn>
Co-developed-by: Xin Tan <tanxin.ctf at gmail.com>
Signed-off-by: Xin Tan <tanxin.ctf at gmail.com>
Signed-off-by: Xin Xiong <xiongx18 at fudan.edu.cn>
---
V1 -> V2: Rewrited the error handling block
---
 drivers/mtd/nand/raw/atmel/nand-controller.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/raw/atmel/nand-controller.c b/drivers/mtd/nand/raw/atmel/nand-controller.c
index f3276ee9e4fe..0efeb5d77be0 100644
--- a/drivers/mtd/nand/raw/atmel/nand-controller.c
+++ b/drivers/mtd/nand/raw/atmel/nand-controller.c
@@ -2060,13 +2060,15 @@ static int atmel_nand_controller_init(struct atmel_nand_controller *nc,
 	nc->mck = of_clk_get(dev->parent->of_node, 0);
 	if (IS_ERR(nc->mck)) {
 		dev_err(dev, "Failed to retrieve MCK clk\n");
-		return PTR_ERR(nc->mck);
+		ret = PTR_ERR(nc->mck);
+		goto out_release_dma;
 	}
 
 	np = of_parse_phandle(dev->parent->of_node, "atmel,smc", 0);
 	if (!np) {
 		dev_err(dev, "Missing or invalid atmel,smc property\n");
-		return -EINVAL;
+		ret = -EINVAL;
+		goto out_release_dma;
 	}
 
 	nc->smc = syscon_node_to_regmap(np);
@@ -2074,10 +2076,20 @@ static int atmel_nand_controller_init(struct atmel_nand_controller *nc,
 	if (IS_ERR(nc->smc)) {
 		ret = PTR_ERR(nc->smc);
 		dev_err(dev, "Could not get SMC regmap (err = %d)\n", ret);
-		return ret;
+		goto out_release_dma;
 	}
 
 	return 0;
+
+out_release_dma:
+	if (nc->caps->has_dma && !atmel_nand_avoid_dma) {
+		if (nc->dmac) {
+			dma_release_channel(nc->dmac);
+			nc->dmac = NULL;
+		}
+	}
+
+	return ret;
 }
 
 static int
-- 
2.25.1