Re: [PATCH v2 2/5] ata: libata-scsi: Fail MODE SELECT for unsupported mode pages

[Niklas Cassel <cassel@kernel.org>]

On Fri, Apr 18, 2025 at 04:55:14PM +0900, Damien Le Moal wrote:
> For devices that do not support CDL, the subpage F2h of the control mode
> page 0Ah should not be supported. However, the function
> ata_mselect_control_ata_feature() does not fail for a device that does
> not have the ATA_DFLAG_CDL device flag set, which can lead to an invalid
> SET FEATURES command (which will be failed by the device) to be issued.
> 
> Modify ata_mselect_control_ata_feature() to return -EOPNOTSUPP if it is
> executed for a device without CDL support. This error code is checked by
> ata_scsi_mode_select_xlat() (through ata_mselect_control()) to fail the
> MODE SELECT command immediately with an ILLEGAL REQUEST / INVALID FIELD
> IN CDB asc/ascq as mandated by the SPC specifications for unsupported
> mode pages.
> 
> Fixes: df60f9c64576 ("scsi: ata: libata: Add ATA feature control sub-page translation")
> Cc: stable@vger.kernel.org
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---
>  drivers/ata/libata-scsi.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index 24e662c837e3..15661b05cb48 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -3896,6 +3896,15 @@ static int ata_mselect_control_ata_feature(struct ata_queued_cmd *qc,
>  	struct ata_taskfile *tf = &qc->tf;
>  	u8 cdl_action;
>  
> +	/*
> +	 * The sub-page f2h should only be supported for devices that support
> +	 * the T2A and T2B command duration limits mode pages (note here the
> +	 * "should" which is what SAT-6 defines). So fail this command if the
> +	 * device does not support CDL.
> +	 */
> +	if (!(dev->flags & ATA_DFLAG_CDL))
> +		return -EOPNOTSUPP;
> +
>  	/*
>  	 * The first four bytes of ATA Feature Control mode page are a header,
>  	 * so offsets in mpage are off by 4 compared to buf.  Same for len.
> @@ -4101,6 +4110,8 @@ static unsigned int ata_scsi_mode_select_xlat(struct ata_queued_cmd *qc)
>  	case CONTROL_MPAGE:
>  		ret = ata_mselect_control(qc, spg, p, pg_len, &fp);
>  		if (ret < 0) {
> +			if (ret == -EOPNOTSUPP)
> +				goto invalid_fld;
>  			fp += hdr_len + bd_len;
>  			goto invalid_param;
>  		}
> -- 

I would prefer if we did not merge this patch, as it is already handled in
higher up in the (only) calling function:
https://github.com/torvalds/linux/blob/v6.15-rc2/drivers/ata/libata-scsi.c#L2582-L2589

We only break if "dev->flags & ATA_DFLAG_CDL && pg == CONTROL_MPAGE"

if this expression is false, we do a fallthrough,
which means fp = 3; goto invalid_fld;


Kind regards,
Niklas