netdev - Re: [PATCH] ptp: guard ptp_clock_gettime() if neither gettimex64 nor

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Message-ID: <9e1ccd0f-ecb6-438e-9763-5ba04bce5928@linux.dev>
Date: Tue, 28 Oct 2025 23:56:22 +0000
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Kuniyuki Iwashima <kuniyu@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>, richardcochran@...il.com,
 andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
 junjie.cao@...el.com, linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 pabeni@...hat.com, syzbot+c8c0e7ccabd456541612@...kaller.appspotmail.com,
 syzkaller-bugs@...glegroups.com, thostet@...gle.com
Subject: Re: [PATCH] ptp: guard ptp_clock_gettime() if neither gettimex64 nor

On 28.10.2025 23:54, Kuniyuki Iwashima wrote:
> On Tue, Oct 28, 2025 at 4:45 PM Vadim Fedorenko
> <vadim.fedorenko@...ux.dev> wrote:
>>
>> On 28.10.2025 23:13, Jakub Kicinski wrote:
>>> On Tue, 28 Oct 2025 15:51:50 +0000 Kuniyuki Iwashima wrote:
>>>> From: Richard Cochran <richardcochran@...il.com>
>>>> Date: Tue, 28 Oct 2025 07:09:41 -0700
>>>>> On Tue, Oct 28, 2025 at 05:51:43PM +0800, Junjie Cao wrote:
>>>>>> Syzbot reports a NULL function pointer call on arm64 when
>>>>>> ptp_clock_gettime() falls back to ->gettime64() and the driver provides
>>>>>> neither ->gettimex64() nor ->gettime64(). This leads to a crash in the
>>>>>> posix clock gettime path.
>>>>>
>>>>> Drivers must provide a gettime method.
>>>>>
>>>>> If they do not, then that is a bug in the driver.
>>>>
>>>> AFAICT, only GVE does not have gettime() and settime(), and
>>>> Tim (CCed) was preparing a fix and mostly ready to post it.
>>>
>>> cc: Vadim who promised me a PTP driver test :) Let's make sure we
>>> tickle gettime/setting in that test..
>>
>> Heh, call gettime/settime is easy. But in case of absence of these callbacks
>> the kernel will crash - not sure we can gather good signal in such case?
> 
> At least we could catch it on NIPA.
> 
> but I suggested Tim adding WARN_ON_ONCE(!info->gettime64 &&
> !info-> getimex64) in ptp_clock_register() so that a developer can
> notice that even while loading a buggy module.

Yeah, that looks like a solution