Re: [PATCH v3] mtd: rawnand: atmel: fix refcount issue in atmel_nand_controller_init

From: Claudiu.Beznea
Date: Fri Mar 04 2022 - 02:34:52 EST


On 02.03.2022 15:27, Xin Xiong wrote:
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>
> 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@xxxxxxxxxxxx>
> Signed-off-by: Xiyu Yang <xiyuyang19@xxxxxxxxxxxx>
> Co-developed-by: Xin Tan <tanxin.ctf@xxxxxxxxx>
> Signed-off-by: Xin Tan <tanxin.ctf@xxxxxxxxx>
> Signed-off-by: Xin Xiong <xiongx18@xxxxxxxxxxxx>
> ---
> 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
>