Re: [PATCH net 2/2] gve: fix NULL dereference due to missing ptp adjfine

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

On 10/08/2026 16:55, Jordan Rhee wrote:
> On Sat, Aug 8, 2026 at 8:27 AM Vadim Fedorenko
> <vadim.fedorenko@linux.dev> wrote:
>>
>> On 07/08/2026 23:43, Harshitha Ramamurthy wrote:
>>> From: Jordan Rhee <jordanrhee@google.com>
>>>
>>> Fix NULL dereference due to missing implementation of adjfine, which can
>>> be triggered from usermode as follows:
>>>
>>> sudo ./testptp -d /dev/ptp0 -f 0
>>> [  551.943697] BUG: kernel NULL pointer dereference, address: 0000000000000000
>>> [...]
>>> [  552.061946] Call Trace:
>>> [  552.064487]  <TASK>
>>> [  552.066681]  ptp_clock_adjtime+0x1c0/0x2c0
>>> [  552.070874]  ? get_clock_desc+0x6b/0xb0
>>> [  552.074825]  pc_clock_adjtime+0x78/0xc0
>>> [  552.078755]  __do_sys_clock_adjtime+0x85/0x110
>>> [  552.083293]  do_syscall_64+0xea/0x610
>>>
>>> Cc: stable@vger.kernel.org
>>> Fixes: acd16380523b ("gve: Add initial PTP device support")
>>> Signed-off-by: Jordan Rhee <jordanrhee@google.com>
>>> Signed-off-by: Harshitha Ramamurthy <hramamurthy@google.com>
>>> ---
>>>    drivers/net/ethernet/google/gve/gve_ptp.c | 6 ++++++
>>>    1 file changed, 6 insertions(+)
>>>
>>> diff --git a/drivers/net/ethernet/google/gve/gve_ptp.c b/drivers/net/ethernet/google/gve/gve_ptp.c
>>> index 06b1cf4a5efc..1d6c59f4ead3 100644
>>> --- a/drivers/net/ethernet/google/gve/gve_ptp.c
>>> +++ b/drivers/net/ethernet/google/gve/gve_ptp.c
>>> @@ -26,6 +26,11 @@ int gve_clock_nic_ts_read(struct gve_priv *priv)
>>>        return 0;
>>>    }
>>>
>>> +static int gve_ptp_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
>>> +{
>>> +     return -EOPNOTSUPP;
>>> +}
>>> +
>>>    static int gve_ptp_gettimex64(struct ptp_clock_info *info,
>>>                              struct timespec64 *ts,
>>>                              struct ptp_system_timestamp *sts)
>>> @@ -60,6 +65,7 @@ static long gve_ptp_do_aux_work(struct ptp_clock_info *info)
>>>    static const struct ptp_clock_info gve_ptp_caps = {
>>>        .owner          = THIS_MODULE,
>>>        .name           = "gve clock",
>>> +     .adjfine        = gve_ptp_adjfine,
>>>        .gettimex64     = gve_ptp_gettimex64,
>>>        .settime64      = gve_ptp_settime64,
>>>        .do_aux_work    = gve_ptp_do_aux_work,
>>
>> .adjtime has to be implemented as well - neither adjfine nor adjtime are
>> checked within ptp_clock_adjtime()
> 
> adjtime() can only be reached if gettimex64() succeeds. Since GVE
> currently returns -EOPNOTSUPP in gettimex64(), ptp_clock_adjtime()
> will short circuit before calling the driver's adjtime callback. We
> will need to provide a stub for adjtime() when we implement
> gettimex64().
> 
> My understanding is that fixes should only address real, reproducible
> issues which is why we only sent adjfine in this patch. If the
> maintainers would prefer we send adjtime() as well, just let us know.
> That said, our preference would be not to delay the other patch in
> this series ("gve: fix zero-length skb frag with header-split").

ah, yeah, I see that gve_ptp_gettimex64 is -EOPNOTSUPP.

Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>