2022-03-04 15:24:07

by Xin Xiong

Subject: [PATCH v4] mtd: rawnand: atmel: fix refcount issue in atmel_nand_controller_init

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 <[email protected]>
Signed-off-by: Xiyu Yang <[email protected]>
Co-developed-by: Xin Tan <[email protected]>
Signed-off-by: Xin Tan <[email protected]>
Signed-off-by: Xin Xiong <[email protected]>
---
V3 -> V4: Removed useless condition check
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..ddd93bc38ea6 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->dmac)
+ dma_release_channel(nc->dmac);
+
+ return ret;
}

static int
--
2.25.1

2022-03-14 19:48:12

by Miquel Raynal

Subject: Re: [PATCH v4] mtd: rawnand: atmel: fix refcount issue in atmel_nand_controller_init

On Fri, 2022-03-04 at 08:53:32 UTC, Xin Xiong wrote:
> 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 <[email protected]>
> Signed-off-by: Xiyu Yang <[email protected]>
> Co-developed-by: Xin Tan <[email protected]>
> Signed-off-by: Xin Tan <[email protected]>
> Signed-off-by: Xin Xiong <[email protected]>
> Reviewed-by: Claudiu Beznea <[email protected]>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next, thanks.

Miquel