Re: [PATCH net v3 3/3] net: ti: icss-iep: Fix possible NULL pointer dereference for perout request

[Roger Quadros <rogerq@kernel.org>]

Meghana,

On 28/03/2025 12:24, Meghana Malladi wrote:
> ICSS IEP driver has flags to check if perout or pps has been enabled
> at any given point of time. Whenever there is request to enable or
> disable the signal, the driver first checks its enabled or disabled
> and acts accordingly.
> 
> After bringing the interface down and up, calling PPS/perout enable
> doesn't work as the driver believes PPS is already enabled,

How? aren't we calling icss_iep_pps_enable(iep, false)?
wouldn't this disable the IEP and clear the iep->pps_enabled flag?

And, what if you brought 2 interfaces of the same ICSS instances up
but put only 1 interface down and up?

> (iep->pps_enabled is not cleared during interface bring down)
> and driver will just return true even though there is no signal.
> Fix this by setting pps and perout flags to false instead of
> disabling perout to avoid possible null pointer dereference.
> 
> 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>
> ---
> 
> Changes from v2(v3-v2):
> - Add Reported-by tag and link to the bug reported by Dan Carpenter <dan.carpenter@linaro.org>
> - drop calling icss_iep_perout_enable() for disabling perout and set perout to false instead
> 
>  drivers/net/ethernet/ti/icssg/icss_iep.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ti/icssg/icss_iep.c b/drivers/net/ethernet/ti/icssg/icss_iep.c
> index b4a34c57b7b4..b70e4c482d74 100644
> --- a/drivers/net/ethernet/ti/icssg/icss_iep.c
> +++ b/drivers/net/ethernet/ti/icssg/icss_iep.c
> @@ -820,9 +820,9 @@ int icss_iep_exit(struct icss_iep *iep)
>  	icss_iep_disable(iep);
>  
>  	if (iep->pps_enabled)
> -		icss_iep_pps_enable(iep, false);
> +		iep->pps_enabled = false;
>  	else if (iep->perout_enabled)
> -		icss_iep_perout_enable(iep, NULL, false);
> +		iep->perout_enabled = false;
>  
>  	return 0;
>  }

-- 
cheers,
-roger