CVE-2026-89694: nfsd: check client ownership when cancelling a copy-notify stateid

CVE-2026-89694: nfsd: check client ownership when cancelling a copy-notify stateid

[Greg Kroah-Hartman]

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

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

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

nfsd: check client ownership when cancelling a copy-notify stateid

On the OFFLOAD_CANCEL path (clp != NULL), manage_cpntf_state() freed the
target cpntf state without checking ownership. The lookup key
st->si_opaque.so_id is allocated cyclically (guessable) and the embedded
clientid is the fixed per-net nn->s2s_cp_cl_id, so any authenticated
NFSv4.2 client could cancel and free another client's copy-notify
stateid.

Compare the creating clientid recorded in state->cp_p_clid against the
requesting client's cl_clientid and return nfserr_bad_stateid on a
mismatch instead of freeing the entry.

The Linux kernel CVE team has assigned CVE-2026-89694 to this issue.


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

	Issue introduced in 5.6 with commit ce0887ac96d35c7105090e166bb0807dc0a0e838 and fixed in 6.12.109 with commit b1eca07303594ca27f5dc360a6946bd7e1f5b04c
	Issue introduced in 5.6 with commit ce0887ac96d35c7105090e166bb0807dc0a0e838 and fixed in 6.18.50 with commit b42dc26a14b4ad5d6daaada11ec4c70744141c25
	Issue introduced in 5.6 with commit ce0887ac96d35c7105090e166bb0807dc0a0e838 and fixed in 7.2.4 with commit d801906165cb5cc250d5cbe44935594e170be3e2
	Issue introduced in 5.6 with commit ce0887ac96d35c7105090e166bb0807dc0a0e838 and fixed in 7.3-rc1 with commit 6bdbfab96e0cf25e5f57dac5c09dc1749751a4bf

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-2026-89694
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/nfsd/nfs4state.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/b1eca07303594ca27f5dc360a6946bd7e1f5b04c
	https://git.kernel.org/stable/c/b42dc26a14b4ad5d6daaada11ec4c70744141c25
	https://git.kernel.org/stable/c/d801906165cb5cc250d5cbe44935594e170be3e2
	https://git.kernel.org/stable/c/6bdbfab96e0cf25e5f57dac5c09dc1749751a4bf