CVE-2026-80927: timekeeping: Check the return value of tk_get_aux_ts64 in __do_adjtimex()

CVE-2026-80927: timekeeping: Check the return value of tk_get_aux_ts64 in __do_adjtimex()

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

timekeeping: Check the return value of tk_get_aux_ts64 in __do_adjtimex()

If the auxiliary clock is disabled during tk_get_aux_ts64() but is enabled
before tks->clock_valid is checked, then uninitialized stackdata will be
used in the calculations and indirectly leaked to userspace.

The same race window also exists after this change and also for the core
timekeeper. But in these cases the only effect would be incorrect
adjustments and this is userspace's responsibility to avoid this.

The Linux kernel CVE team has assigned CVE-2026-80927 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.17 with commit 4eca49d0b621b314ac7c80f363932ec6f6c8abc8 and fixed in 6.18.50 with commit fecf1e37775269ad38c172b468ad4ecc3968aa63
	Issue introduced in 6.17 with commit 4eca49d0b621b314ac7c80f363932ec6f6c8abc8 and fixed in 7.2.4 with commit bc59dac50cb45a725f7a50760c7cc72a0964f722
	Issue introduced in 6.17 with commit 4eca49d0b621b314ac7c80f363932ec6f6c8abc8 and fixed in 7.3-rc1 with commit 4b61084b11bcecce86d03804ff30f8d7b465593c

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-80927
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	kernel/time/timekeeping.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/fecf1e37775269ad38c172b468ad4ecc3968aa63
	https://git.kernel.org/stable/c/bc59dac50cb45a725f7a50760c7cc72a0964f722
	https://git.kernel.org/stable/c/4b61084b11bcecce86d03804ff30f8d7b465593c