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@fudan.edu.cn>
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Co-developed-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn>
---
V2 -> V3: Removed redundant lines
V1 -> V2: Rewrited the error handling block
---
 drivers/mtd/nand/raw/atmel/nand-controller.c | 14 +++++++++++---
 1 file changed, 11 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..3dc4a4bacde5 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 +2076,16 @@ 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 && nc->dmac)
+		dma_release_channel(nc->dmac);
+
+	return ret;
 }
 
 static int
-- 
2.25.1

On 02.03.2022 15:27, Xin Xiong wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> 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@fudan.edu.cn>
> Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Co-developed-by: Xin Tan <tanxin.ctf@gmail.com>
> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
> Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn>
> ---
> V2 -> V3: Removed redundant lines
> V1 -> V2: Rewrited the error handling block
> ---
>  drivers/mtd/nand/raw/atmel/nand-controller.c | 14 +++++++++++---
>  1 file changed, 11 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..3dc4a4bacde5 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 +2076,16 @@ 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 && nc->dmac)

As Boris also suggested previously, checking nc->dmac should be enough here.

> +               dma_release_channel(nc->dmac);
> +
> +       return ret;
>  }
> 
>  static int
> --
> 2.25.1
>