Re: [PATCH] mmc: dw_mmc: Add a defensive check to prevent potential null-pointer dereferences in dw_mci_runtime_resume()

[Shawn Lin <shawn.lin@rock-chips.com>]

Hi Tuo,

在 2025/12/12 星期五 0:13, Tuo Li 写道:
> In this function, the variable host->slot is checked and then dereferenced
> in several places which indicates it can be NULL, for example:
> 
>    if (host->slot && host->slot->mmc->pm_flags & MMC_PM_KEEP_POWER)
> 		dw_mci_set_ios(host->slot->mmc, &host->slot->mmc->ios);
> 
> However, in the following cases, host->slot is dereferenced without a
> preceding NULL check, which introduces a risk of null-pointer dereference:
> 
>    dw_mci_setup_bus(host->slot, true);
> 
>    if (sdio_irq_claimed(host->slot->mmc))
>      __dw_mci_enable_sdio_irq(host->slot, 1);
> 
>    dw_mci_enable_cd(host);
> 
> To prevent such issues, add a defensive check to ensure host->slot is not
> NULL before dereferencing it.
> 

Thanks for your patch. we plan to remove the slot design
entirely soon, probably this cycle.

> Signed-off-by: Tuo Li <islituo@gmail.com>
> ---
>   drivers/mmc/host/dw_mmc.c | 17 ++++++++++-------
>   1 file changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 9e74b675e92d..e74dea0a32d4 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -3670,15 +3670,18 @@ int dw_mci_runtime_resume(struct device *dev)
>   	if (host->slot && host->slot->mmc->pm_flags & MMC_PM_KEEP_POWER)
>   		dw_mci_set_ios(host->slot->mmc, &host->slot->mmc->ios);
>   
> -	/* Force setup bus to guarantee available clock output */
> -	dw_mci_setup_bus(host->slot, true);
>   
> -	/* Re-enable SDIO interrupts. */
> -	if (sdio_irq_claimed(host->slot->mmc))
> -		__dw_mci_enable_sdio_irq(host->slot, 1);
> +	if (host->slot) {
> +		/* Force setup bus to guarantee available clock output */
> +		dw_mci_setup_bus(host->slot, true);
>   
> -	/* Now that slots are all setup, we can enable card detect */
> -	dw_mci_enable_cd(host);
> +		/* Re-enable SDIO interrupts. */
> +		if (sdio_irq_claimed(host->slot->mmc))
> +			__dw_mci_enable_sdio_irq(host->slot, 1);
> +
> +		/* Now that slots are all setup, we can enable card detect */
> +		dw_mci_enable_cd(host);
> +	}
>   
>   	return 0;
>