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

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Message-ID: <cd154e3c-0cac-4ead-a3d0-39dc617efa74@linux.dev>
Date: Tue, 28 Oct 2025 23:45:13 +0000
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Jakub Kicinski <kuba@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>
Cc: 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 23:13, 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?