Re: [PATCH net v4 3/3] net: ti: icss-iep: Fix possible NULL pointer dereference for perout request

[Jacob Keller <jacob.e.keller@intel.com>]

On 4/15/2025 2:05 AM, Meghana Malladi wrote:
> The ICSS IEP driver tracks perout and pps enable state with flags.
> Currently when disabling pps and perout signals during icss_iep_exit(),
> results in NULL pointer dereference for perout.
> 
> To fix the null pointer dereference issue, the icss_iep_perout_enable_hw
> function can be modified to directly clear the IEP CMP registers when
> disabling PPS or PEROUT, without referencing the ptp_perout_request
> structure, as its contents are irrelevant in this case.
> 
> Fixes: 9b115361248d ("net: ti: icssg-prueth: Fix clearing of IEP_CMP_CFG registers during iep_init")
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Closes: https://lore.kernel.org/all/7b1c7c36-363a-4085-b26c-4f210bee1df6@stanley.mountain/
> Signed-off-by: Meghana Malladi <m-malladi@ti.com>
> ---
> 

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

> Changes from v3 (v4-v3):
> - Fix the logic in icss_iep_perout_enable_hw() to clear IEP registers
>   when disabling periodic signal
> 
>  drivers/net/ethernet/ti/icssg/icss_iep.c | 121 +++++++++++------------
>  1 file changed, 58 insertions(+), 63 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ti/icssg/icss_iep.c b/drivers/net/ethernet/ti/icssg/icss_iep.c
> index b4a34c57b7b4..2a1c43316f46 100644
> --- a/drivers/net/ethernet/ti/icssg/icss_iep.c
> +++ b/drivers/net/ethernet/ti/icssg/icss_iep.c
> @@ -430,64 +446,39 @@ static int icss_iep_perout_enable_hw(struct icss_iep *iep,
>  		if (ret)
>  			return ret;
>  
> -		if (on) {
> -			/* Configure CMP */
> -			regmap_write(iep->map, ICSS_IEP_CMP1_REG0, lower_32_bits(cmp));
> -			if (iep->plat_data->flags & ICSS_IEP_64BIT_COUNTER_SUPPORT)
> -				regmap_write(iep->map, ICSS_IEP_CMP1_REG1, upper_32_bits(cmp));
> -			/* Configure SYNC, based on req on width */
> -			regmap_write(iep->map, ICSS_IEP_SYNC_PWIDTH_REG,
> -				     div_u64(ns_width, iep->def_inc));
> -			regmap_write(iep->map, ICSS_IEP_SYNC0_PERIOD_REG, 0);
> -			regmap_write(iep->map, ICSS_IEP_SYNC_START_REG,
> -				     div_u64(ns_start, iep->def_inc));
> -			regmap_write(iep->map, ICSS_IEP_SYNC_CTRL_REG, 0); /* one-shot mode */
> -			/* Enable CMP 1 */
> -			regmap_update_bits(iep->map, ICSS_IEP_CMP_CFG_REG,
> -					   IEP_CMP_CFG_CMP_EN(1), IEP_CMP_CFG_CMP_EN(1));
> -		} else {
> -			/* Disable CMP 1 */
> -			regmap_update_bits(iep->map, ICSS_IEP_CMP_CFG_REG,
> -					   IEP_CMP_CFG_CMP_EN(1), 0);
> -
> -			/* clear regs */
> -			regmap_write(iep->map, ICSS_IEP_CMP1_REG0, 0);
> -			if (iep->plat_data->flags & ICSS_IEP_64BIT_COUNTER_SUPPORT)
> -				regmap_write(iep->map, ICSS_IEP_CMP1_REG1, 0);
> -		}
> +		/* Configure CMP */
> +		regmap_write(iep->map, ICSS_IEP_CMP1_REG0, lower_32_bits(cmp));
> +		if (iep->plat_data->flags & ICSS_IEP_64BIT_COUNTER_SUPPORT)
> +			regmap_write(iep->map, ICSS_IEP_CMP1_REG1, upper_32_bits(cmp));
> +		/* Configure SYNC, based on req on width */
> +		regmap_write(iep->map, ICSS_IEP_SYNC_PWIDTH_REG,
> +			     div_u64(ns_width, iep->def_inc));
> +		regmap_write(iep->map, ICSS_IEP_SYNC0_PERIOD_REG, 0);
> +		regmap_write(iep->map, ICSS_IEP_SYNC_START_REG,
> +			     div_u64(ns_start, iep->def_inc));
> +		regmap_write(iep->map, ICSS_IEP_SYNC_CTRL_REG, 0); /* one-shot mode */
> +		/* Enable CMP 1 */
> +		regmap_update_bits(iep->map, ICSS_IEP_CMP_CFG_REG,
> +				   IEP_CMP_CFG_CMP_EN(1), IEP_CMP_CFG_CMP_EN(1));

Nice to see this also has a marked improvement with removing a level of
indentation.

> @@ -498,11 +489,21 @@ static int icss_iep_perout_enable(struct icss_iep *iep,
>  {
>  	int ret = 0;
>  
> +	if (!on)
> +		goto disable;
> +
>  	/* Reject requests with unsupported flags */
>  	if (req->flags & ~(PTP_PEROUT_DUTY_CYCLE |
>  			  PTP_PEROUT_PHASE))
>  		return -EOPNOTSUPP;
>  

This likely causes a textual conflict with my .supported_perout_flags
patch. It looks like it wouldn't be too difficult to resolve though.

> +	/* Set default "on" time (1ms) for the signal if not passed by the app */
> +	if (!(req->flags & PTP_PEROUT_DUTY_CYCLE)) {
> +		req->on.sec = 0;
> +		req->on.nsec = NSEC_PER_MSEC;
> +	}
> +

Regards,
Jake