CVE-2026-68455: liveupdate: validate session type before performing operation

From: Greg Kroah-Hartman <[email protected]>

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

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

liveupdate: validate session type before performing operation

The sessions ioctls are not applicable to all session types. PRESERVE_FD
is only applicable to outgoing sessions. RETRIEVE_FD and FINISH are only
valid for incoming session. Calling a incoming ioctl on an outgoing
session is invalid and can cause file handlers to run into unexpected
errors.

For example, a user can create a (outgoing) session, preserve a memfd,
and then immediately do a retrieve without doing a kexec in between.
This would result in memfd's retrieve handler to run. The handlers
expects to be called from a post-kexec context, and will try to do a
kho_restore_vmalloc() or kho_restore_folio() to try and restore memory.

KHO catches this (thanks to KHO_PAGE_MAGIC) and returns an error, but
since this is considered an internal error and KHO throws out a bunch of
WARN()s.

Associate a type with each ioctl op and validate the type in
luo_session_ioctl() before dispatching the ioctl handler to make sure
the op is being called for the right session type.

The Linux kernel CVE team has assigned CVE-2026-68455 to this issue.


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

	Issue introduced in 6.19 with commit 16cec0d265219f14a7fcebcc43aeb69205adba56 and fixed in 7.1.5 with commit 3dc8a46d08a8a060d4128e9f497060b8d03c1595
	Issue introduced in 6.19 with commit 16cec0d265219f14a7fcebcc43aeb69205adba56 and fixed in 7.2-rc1 with commit 507e3b479f9c6d85135eb5e1a77fb3fddb259ad8

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-2026-68455
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/liveupdate/luo_session.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/3dc8a46d08a8a060d4128e9f497060b8d03c1595
	https://git.kernel.org/stable/c/507e3b479f9c6d85135eb5e1a77fb3fddb259ad8