CVE-2026-89709: lockd, nfsd: RCU-protect nlmsvc_ops dispatch

CVE-2026-89709: lockd, nfsd: RCU-protect nlmsvc_ops dispatch

[Greg Kroah-Hartman]

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

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

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

lockd, nfsd: RCU-protect nlmsvc_ops dispatch

nlmsvc_ops is published by nfsd_lockd_init() and cleared by
nfsd_lockd_shutdown() with plain stores, while lockd dereferences
it unguarded from dispatch sites in fs/lockd/svcsubs.c. The pointer
targets nfsd's .rodata and the fopen/fclose callbacks live in nfsd's
.text, so a stale load after rmmod nfsd results in either a NULL
deref or a module-text use-after-free.

Declare nlmsvc_ops as __rcu, publish via rcu_assign_pointer(), clear
via RCU_INIT_POINTER() + synchronize_rcu(). Add a struct module
*owner field to nlmsvc_binding and pin the module across indirect
calls with try_module_get/module_put. When the binding is torn down,
fall back to fput() to avoid leaking struct file references.

The Linux kernel CVE team has assigned CVE-2026-89709 to this issue.


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

	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 7.2.4 with commit 3c461a1820088fb5889d73a6522369bde45527a9
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 7.3-rc1 with commit 641e5e20852359b8c31149be4598884e30652f60

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-2026-89709
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:
	fs/lockd/svc.c
	fs/lockd/svc4proc.c
	fs/lockd/svcproc.c
	fs/lockd/svcsubs.c
	fs/nfsd/lockd.c
	include/linux/lockd/bind.h


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/3c461a1820088fb5889d73a6522369bde45527a9
	https://git.kernel.org/stable/c/641e5e20852359b8c31149be4598884e30652f60