linux-kernel - Re: [PATCH v2] ptp: ocp: fix NULL deref in __handle

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Message-ID: <e369b3ac-c1ba-4188-bd12-391a9932ce6e@linux.dev>
Date: Tue, 15 Apr 2025 10:58:23 +0100
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Sagi Maimon <maimon.sagi@...il.com>, jonathan.lemon@...il.com,
 richardcochran@...il.com, andrew+netdev@...n.ch, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2] ptp: ocp: fix NULL deref in __handle_s for irig/dcf

On 15/04/2025 07:46, 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.

Ok, looks like I misread the patch previously. IRIG and DCF registers
are mapped unconditionally for OCP TimeCard. The functions you are
trying to fix are HW-specific functions which you decided to reuse for
your hardware. If your hardware doesn't support this function, you have
to implement your own HW-specific callbacks used in ocp_adva_sma_op
structure. I have to take back my Rb tag, and for this patch it's
definitely NAck.

> 
> Fixes: b286f4e87e32 ("serial: core: Move tty and serdev to be children of serial core port device")
> Reviewed-by: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
> Signed-off-by: Sagi Maimon <maimon.sagi@...il.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)
> +		ptp_ocp_irig_in(bp, val & 0x00100010);
> +	if (bp->dcf_out)
> +		ptp_ocp_dcf_in(bp, val & 0x00200020);
>   }
>   
>   static u32