Re: [PATCH] mci: Fix erase_grp_size extraction for SD with csd_struct v0

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Sascha,

On 01.10.24 11:57, Sascha Hauer wrote:
> In mci_extract_erase_group_size() we test for (IS_SD() && csd_struct_v1)
> which means that for non csd_struct_v1 SD cards we fall into the MMC
> path and evaluate ext_csd. This doesn't exist for SD cards and the
> code crashes with a NULL pointer deref.
> 
> Fix this by always falling into the SD case for SD cards. Add the
> missing erase_grp_size extraction for csd_struct v0 cards. The code
> for that is taken from the corresponding Linux code.
> 
> Fixes: 91a11c7d50 ("mci: add support for discarding write blocks")
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

Thanks for the fix,
Ahmad

> ---
>  drivers/mci/mci-core.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
> index ec4a5c0749..48a3df9ec9 100644
> --- a/drivers/mci/mci-core.c
> +++ b/drivers/mci/mci-core.c
> @@ -1228,9 +1228,20 @@ static void mci_extract_erase_group_size(struct mci *mci)
>  		return;
>  
>  
> -	if (IS_SD(mci) && UNSTUFF_BITS(mci->csd, 126, 2) != 0) {
> -		/* For SD with csd_struct v1, erase group is always one sector */
> -		mci->erase_grp_size = 1;
> +	if (IS_SD(mci)) {
> +		if (UNSTUFF_BITS(mci->csd, 126, 2) == 0) {
> +			unsigned int write_blkbits = UNSTUFF_BITS(mci->csd, 22, 4);
> +
> +			if (UNSTUFF_BITS(mci->csd, 46, 1)) {
> +				mci->erase_grp_size = 1;
> +			} else if (write_blkbits >= 9) {
> +				mci->erase_grp_size = UNSTUFF_BITS(mci->csd, 39, 7) + 1;
> +				mci->erase_grp_size <<= write_blkbits - 9;
> +			}
> +		} else {
> +			/* For SD with csd_struct v1, erase group is always one sector */
> +			mci->erase_grp_size = 1;
> +		}
>  	} else {
>  		if (mci->ext_csd[EXT_CSD_ERASE_GROUP_DEF] & 0x01) {
>  			/* Read out group size from ext_csd */


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