Re: [PATCH net v1] ptp: fix NULL deref when adjtime/adjfine are missing

[Vadim Fedorenko <vadim.fedorenko@linux.dev>]

On 26/08/2026 11:10, Xuanqiang Luo wrote:
> From: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
> 
> ptp_clock_adjtime() invokes ->adjtime and ->adjfine unconditionally,
> but both callbacks are optional. 

Could you please link to the source of this statement?

clock_adjtime() with ADJ_SETOFFSET
> or ADJ_FREQUENCY therefore oopses on a PHC that implements neither.
> 
> iavf registers such a read-only clock: no adjtime/adjfine, and
> max_adj left at 0. ADJ_SETOFFSET hits the NULL ->adjtime after the
> offset is validated. ADJ_FREQUENCY with freq 0 converts to 0 ppb,
> passes the max_adj check, and hits the NULL ->adjfine.
> 
> Return -EOPNOTSUPP when the requested callback is missing, as the
> adjphase path already does, rather than adding driver stubs.

If PHC does not implement adjtime/adjfine/adjphase then it is a free-
running clock. ptp_clock_adjtime() has the check for such clocks.
To properly fix core part we have to extend ptp_clock and/or
ptp_clock_info to properly signal that registered clock is
free-running/read-only.