CVE-2026-89765: timers/itimer: Zero-init old itimerval before copy to userspace

CVE-2026-89765: timers/itimer: Zero-init old itimerval before copy to userspace

[Greg Kroah-Hartman]

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

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

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

timers/itimer: Zero-init old itimerval before copy to userspace

On native sparc64, struct __kernel_old_timeval contains a four-byte hole
after tv_usec because tv_sec is 64-bit while __kernel_suseconds_t is 32-bit.
put_itimerval() fills only the named fields in a stack-allocated
__kernel_old_itimerval and copies the entire object to userspace, so
getitimer() can expose the two padding holes.

Zero-initialize the aggregate before assigning the fields so implicit
padding is deterministic before it crosses the user/kernel boundary.

The Linux kernel CVE team has assigned CVE-2026-89765 to this issue.


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

	Fixed in 6.12.109 with commit 4c66719dd1e4023c5e3f7d050f1bbefec3dfbeb4
	Fixed in 6.18.50 with commit 2bf5e8f7c9bf4ad3be343a9a6e3e50a34264d25e
	Fixed in 7.2.4 with commit 00ef529a5402f41eb1d227916437e237450719f9
	Fixed in 7.3-rc1 with commit 18c7d85864e554adc8fad1e8d2e9d2cb6c3911c8

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-2026-89765
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/itimer.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/4c66719dd1e4023c5e3f7d050f1bbefec3dfbeb4
	https://git.kernel.org/stable/c/2bf5e8f7c9bf4ad3be343a9a6e3e50a34264d25e
	https://git.kernel.org/stable/c/00ef529a5402f41eb1d227916437e237450719f9
	https://git.kernel.org/stable/c/18c7d85864e554adc8fad1e8d2e9d2cb6c3911c8