Re: [PATCH v2] ptp: ocp: fix NULL deref in __handle_s for irig/dcf

[Michal Swiatkowski <michal.swiatkowski@linux.intel.com>]

On Tue, Apr 15, 2025 at 09:46:38AM +0300, Sagi Maimon wrote:
> SMA store/get operations via sysfs can call __handle_signal_outputs
> or __handle_signal_inputs while irig and dcf pointers remain
> uninitialized. This leads to a NULL pointer dereference in
> __handle_s. Add NULL checks for irig and dcf to prevent crashes.
> 
> Fixes: b286f4e87e32 ("serial: core: Move tty and serdev to be children of serial core port device")
> Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
> Signed-off-by: Sagi Maimon <maimon.sagi@gmail.com>
> ---
> Addressed comments from Paolo Abeni:
>  - https://www.spinics.net/lists/netdev/msg1082406.html
> Changes since v1:
>  - Expanded commit message to clarify the NULL dereference scenario.
> ---
>  drivers/ptp/ptp_ocp.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/ptp/ptp_ocp.c b/drivers/ptp/ptp_ocp.c
> index 7945c6be1f7c..4e4a6f465b01 100644
> --- a/drivers/ptp/ptp_ocp.c
> +++ b/drivers/ptp/ptp_ocp.c
> @@ -2434,15 +2434,19 @@ ptp_ocp_dcf_in(struct ptp_ocp *bp, bool enable)
>  static void
>  __handle_signal_outputs(struct ptp_ocp *bp, u32 val)
>  {
> -	ptp_ocp_irig_out(bp, val & 0x00100010);
> -	ptp_ocp_dcf_out(bp, val & 0x00200020);
> +	if (bp->irig_out)
> +		ptp_ocp_irig_out(bp, val & 0x00100010);
> +	if (bp->dcf_out)
> +		ptp_ocp_dcf_out(bp, val & 0x00200020);
>  }
>  
>  static void
>  __handle_signal_inputs(struct ptp_ocp *bp, u32 val)
>  {
> -	ptp_ocp_irig_in(bp, val & 0x00100010);
> -	ptp_ocp_dcf_in(bp, val & 0x00200020);
> +	if (bp->irig_out)
Why not irig_in? Can we asssume that "in" isn't NULL if "out" isn't?

> +		ptp_ocp_irig_in(bp, val & 0x00100010);
> +	if (bp->dcf_out)
The same here.

> +		ptp_ocp_dcf_in(bp, val & 0x00200020);

Just my opinion, I will move these checks into ptp_ocp_...() functions
as bp is passed to a function not bp->sth.

>  }
>  
>  static u32
> -- 
> 2.47.0