Bug#1128522: linux-image-6.12.73+deb13-amd64: Recent security kernels break chrony's use of PHC clock (6.1.162, 6.12.73)

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From	Salvatore Bonaccorso <carnil@debian.org>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#1128522: linux-image-6.12.73+deb13-amd64: Recent security kernels break chrony's use of PHC clock (6.1.162, 6.12.73)
Date	Fri, 20 Feb 2026 21:50:02 +0100
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Control: reassign -1 src:chrony
Control: forcemerge 1127659 -1

Hi,

On Fri, Feb 20, 2026 at 02:20:00PM -0600, maney wrote:
> Package: linux-image-6.12.73+deb13-amd64
> Version: linux-image-6.12.73+deb13-amd64
> Severity: normal
> 
> Observed on amd64 machines with both Bookworm (6.1.162) and Trixie (6.12.73)
> current security linux-image releases. Different CPU familys (Jaguar and
> Ryzen). Different chrony versions (4.3-2+deb12u1, 4.6.1-3).
> 
> To observe problem, with security kernels installed, setup a PHC clock
> source for the existing I210 interface, eg.
> 
> refclock PHC /dev/ptp0:extpps
> 
> Observe error when starting chrony:
> 
> chronyd[837]: Fatal error : Could not enable external PHC timestamping
> 
> (wording may be different between the two systems, this was Trixie)
> 
> Both work fine under previous kernels 6.1.159 and 6.12.73 (I do not
> guarantee there weren't any other versions released between these and the
> recent security, neither machine is exposed to the internet and so don't
> always get updated immediately.)
> 
> In both cases chrony's use of the PHC for timestamping appears unimpaired by
> the kernels that fail the PHC refclock. The bookworm platform has linuxptp
> installed. phc_ctl and ts2phc work fine with either kernel.
> 
> I left the severity at normal, but it's much more serious to a machine
> that's syncing to a PPS source like this.
> 
> Workaround: roll back those security kernels, of course. And test any future
> releases for this issue, of course.

This is #1127659. Background the issue will not be fixed in src:linux
as the commit introducing this is considered a security fix, but the
maintainer of src:chrony will is preparing updates.

Regards,
Salvatore

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Bug#1128522: linux-image-6.12.73+deb13-amd64: Recent security kernels break chrony's use of PHC clock (6.1.162, 6.12.73) maney <maney@two14.net> - 2026-02-20 21:30 +0100
  Processed: Re: Bug#1128522: linux-image-6.12.73+deb13-amd64:  Recent security kernels break chrony's use of PHC clock (6.1.162, 6.12.73) "Debian Bug Tracking System" <owner@bugs.debian.org> - 2026-02-20 21:50 +0100
  Bug#1128522: linux-image-6.12.73+deb13-amd64: Recent security kernels break chrony's use of PHC clock (6.1.162, 6.12.73) Salvatore Bonaccorso <carnil@debian.org> - 2026-02-20 21:50 +0100

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