If there is no suitable resource, platform_get_resource() will return
NULL.
Therefore in order to avoid the dereference of the NULL pointer, it
should be better to check the 'res'.

Fixes: 27cbd7e815a8 ("mmc: sh_mmcif: rework dma channel handling")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
---
 drivers/mmc/host/sh_mmcif.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/mmc/host/sh_mmcif.c b/drivers/mmc/host/sh_mmcif.c
index e5e457037235..45dfa3b0be9c 100644
--- a/drivers/mmc/host/sh_mmcif.c
+++ b/drivers/mmc/host/sh_mmcif.c
@@ -405,6 +405,9 @@ static int sh_mmcif_dma_slave_config(struct sh_mmcif_host *host,
 	struct dma_slave_config cfg = { 0, };
 
 	res = platform_get_resource(host->pd, IORESOURCE_MEM, 0);
+	if (!res)
+		return -EINVAL;
+
 	cfg.direction = direction;
 
 	if (direction == DMA_DEV_TO_MEM) {
-- 
2.25.1

On Wed, 5 Jan 2022 at 10:41, Jiasheng Jiang <jiasheng@iscas.ac.cn> wrote:
>
> If there is no suitable resource, platform_get_resource() will return
> NULL.
> Therefore in order to avoid the dereference of the NULL pointer, it
> should be better to check the 'res'.
>
> Fixes: 27cbd7e815a8 ("mmc: sh_mmcif: rework dma channel handling")

I think this fixes tag is wrong. The problem seems to have been there
way before this point.

I suggest we instead just tag it for stable - and then let it be
applied to whatever kernel version it can. Does it make sense to you?

Kind regards
Uffe

> Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
> ---
>  drivers/mmc/host/sh_mmcif.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/mmc/host/sh_mmcif.c b/drivers/mmc/host/sh_mmcif.c
> index e5e457037235..45dfa3b0be9c 100644
> --- a/drivers/mmc/host/sh_mmcif.c
> +++ b/drivers/mmc/host/sh_mmcif.c
> @@ -405,6 +405,9 @@ static int sh_mmcif_dma_slave_config(struct sh_mmcif_host *host,
>         struct dma_slave_config cfg = { 0, };
>
>         res = platform_get_resource(host->pd, IORESOURCE_MEM, 0);
> +       if (!res)
> +               return -EINVAL;
> +
>         cfg.direction = direction;
>
>         if (direction == DMA_DEV_TO_MEM) {
> --
> 2.25.1
>