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Fencer Vulns
medium 5.5

CVE-2024-26629 json

nfsd: fix RELEASE_LOCKOWNER

published 2024-03-13 2 y ago modified 2026-10-15 25 d ago also EUVD-2024-23891

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 9%
public exploits
0
none known

Summary

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

nfsd: fix RELEASE_LOCKOWNER

The test on so_count in nfsd4_release_lockowner() is nonsense and harmful. Revert to using check_for_locks(), changing that to not sleep.

First: harmful. As is documented in the kdoc comment for nfsd4_release_lockowner(), the test on so_count can transiently return a false positive resulting in a return of NFS4ERR_LOCKS_HELD when in fact no locks are held. This is clearly a protocol violation and with the Linux NFS client it can cause incorrect behaviour.

If RELEASE_LOCKOWNER is sent while some other thread is still processing a LOCK request which failed because, at the time that request was received, the given owner held a conflicting lock, then the nfsd thread processing that LOCK request can hold a reference (conflock) to the lock owner that causes nfsd4_release_lockowner() to return an incorrect error.

The Linux NFS client ignores that NFS4ERR_LOCKS_HELD error because it never sends NFS4_RELEASE_LOCKOWNER without first releasing any locks, so it knows that the error is impossible. It assumes the lock owner was in fact released so it feels free to use the same lock owner identifier in some later locking request.

When it does reuse a lock owner identifier for which a previous RELEASE failed, it will naturally use a lock_seqid of zero. However the server, which didn't release the lock owner, will expect a larger lock_seqid and so will respond with NFS4ERR_BAD_SEQID.

So clearly it is harmful to allow a false positive, which testing so_count allows.

The test is nonsense because ... well... it doesn't mean anything.

so_count is the sum of three different counts. 1/ the set of states listed on so_stateids 2/ the set of active vfs locks owned by any of those states 3/ various transient counts such as for conflicting locks.

When it is tested against '2' it is clear that one of these is the transient reference obtained by find_lockowner_str_locked(). It is not clear what the other one is expected to be.

In practice, the count is often 2 because there is precisely one state on so_stateids. If there were more, this would fail.

In my testing I see two circumstances when RELEASE_LOCKOWNER is called. In one case, CLOSE is called before RELEASE_LOCKOWNER. That results in all the lock states being removed, and so the lockowner being discarded (it is removed when there are no more references which usually happens when the lock state is discarded). When nfsd4_release_lockowner() finds that the lock owner doesn't exist, it returns success.

The other case shows an so_count of '2' and precisely one state listed in so_stateid. It appears that the Linux client uses a separate lock owner for each file resulting in one lock state per lock owner, so this test on '2' is safe. For another client it might not be safe.

So this patch changes check_for_locks() to use the (newish) find_any_file_locked() so that it doesn't take a reference on the nfs4_file and so never calls nfsd_file_put(), and so never sleeps. With this check is it safe to restore the use of check_for_locks() rather than testing so_count against the mysterious '2'.

Patch / fix

  • Linux Linux 4.10, 4.15, 4.19.306, 5.5, 5.10.220, 5.15.154, 5.18, 5.19, 6.1.79, 6.6.15, 6.7.3, 6.8
  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem V1.1.1
  • linux Debian 12 6.1.82-1
  • linux Debian 14, Debian 13 6.6.15-1

debian advisories DEBIAN-CVE-2024-26629

  • linux Ubuntu 22.04 LTS 5.15.0-116.126
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1065.71
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1064.72
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1062.68
  • linux-ibm Ubuntu 22.04 LTS 5.15.0-1058.61
  • linux-kvm Ubuntu 22.04 LTS 5.15.0-1062.67
  • linux-azure Ubuntu 22.04 LTS 5.15.0-1068.77
  • linux-gkeop Ubuntu 22.04 LTS 5.15.0-1048.55

ubuntu advisories UBUNTU-CVE-2024-26629

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 9 5.14.0-427.35.1.el9_4
  • rv RHEL 9 5.14.0-427.35.1.el9_4
  • perf RHEL 9 5.14.0-427.35.1.el9_4
  • rtla RHEL 9 5.14.0-427.35.1.el9_4
  • bpftool RHEL 9 7.3.0-427.35.1.el9_4
  • libperf RHEL 9 5.14.0-427.35.1.el9_4
  • kernel-rt RHEL 9 5.14.0-427.35.1.el9_4
  • kernel-64k RHEL 9 5.14.0-427.35.1.el9_4

red hat advisories RHSA-2024:6567

  • kernel-azure SLE Module for Public Cloud 15 SP5, openSUSE Leap 15.5 5.14.21-150500.33.48.1
  • kernel-syms-azure SLE Module for Public Cloud 15 SP5, openSUSE Leap 15.5 5.14.21-150500.33.48.1
  • kernel-source-azure SLE Module for Public Cloud 15 SP5, openSUSE Leap 15.5 5.14.21-150500.33.48.1
  • dtb-aarch64 openSUSE Leap 15.5 5.14.21-150500.55.59.1
  • kernel-64kb SLE Module for Basesystem 15 SP5, openSUSE Leap 15.5 5.14.21-150500.55.59.1
  • kernel-syms SLE Module for Development Tools 15 SP5, openSUSE Leap 15.5 5.14.21-150500.55.59.1
  • kernel-obs-qa openSUSE Leap 15.5 5.14.21-150500.55.59.1
  • kernel-source SLE Module for Development Tools 15 SP5, SLE Module for Basesystem 15 SP5, openSUSE Leap 15.5 5.14.21-150500.55.59.1

suse advisories SUSE-SU-2024:1490-1SUSE-SU-2024:1480-1SUSE-SU-2024:1466-1

  • kernel AlmaLinux 9 5.14.0-427.35.1.el9_4
  • rv AlmaLinux 9 5.14.0-427.35.1.el9_4
  • perf AlmaLinux 9 5.14.0-427.35.1.el9_4
  • rtla AlmaLinux 9 5.14.0-427.35.1.el9_4
  • bpftool AlmaLinux 9 7.3.0-427.35.1.el9_4
  • libperf AlmaLinux 9 5.14.0-427.35.1.el9_4
  • kernel-rt AlmaLinux 9 5.14.0-427.35.1.el9_4
  • kernel-64k AlmaLinux 9 5.14.0-427.35.1.el9_4

almalinux advisories ALSA-2024:6567

  • kernel Rocky Linux 9 5.14.0-427.35.1.el9_4.cloud.1.0
  • kernel Rocky Linux 9 5.14.0-427.35.1.el9_4

rocky linux advisories RXSA-2024:6567RLSA-2024:6567

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2024-26629 updated cvss 5.5

kernel: nfsd: fix RELEASE_LOCKOWNER

  • Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-427.35.1.el9_4, perf 5.14.0-427.35.1.el9_4, rtla 5.14.0-427.35.1.el9_4, kernel-devel-matched 5.14.0-427.35.1.el9_4, kernel-64k-devel-matched 5.14.0-427.35.1.el9_4, kernel-debug-devel-matched 5.14.0-427.35.1.el9_4, +6 more Red Hat Enterprise Linux BaseOS (v. 9) bpftool 7.3.0-427.35.1.el9_4, kernel 5.14.0-427.35.1.el9_4, kernel-64k 5.14.0-427.35.1.el9_4, kernel-core 5.14.0-427.35.1.el9_4, kernel-tools 5.14.0-427.35.1.el9_4, python3-perf 5.14.0-427.35.1.el9_4, +28 more Red Hat Enterprise Linux CRB (v. 9) libperf 5.14.0-427.35.1.el9_4, kernel-debuginfo-common-s390x 5.14.0-427.35.1.el9_4, kernel-debuginfo-common-x86_64 5.14.0-427.35.1.el9_4, kernel-debuginfo-common-aarch64 5.14.0-427.35.1.el9_4, kernel-debuginfo-common-ppc64le 5.14.0-427.35.1.el9_4 Red Hat Enterprise Linux NFV (v. 9) kernel-rt 5.14.0-427.35.1.el9_4, kernel-rt-kvm 5.14.0-427.35.1.el9_4, kernel-rt-core 5.14.0-427.35.1.el9_4, kernel-rt-modules 5.14.0-427.35.1.el9_4, kernel-rt-debug-kvm 5.14.0-427.35.1.el9_4, kernel-rt-debug-core 5.14.0-427.35.1.el9_4, +6 more Red Hat Enterprise Linux RT (v. 9) kernel-rt 5.14.0-427.35.1.el9_4, kernel-rt-core 5.14.0-427.35.1.el9_4, kernel-rt-modules 5.14.0-427.35.1.el9_4, kernel-rt-debug-core 5.14.0-427.35.1.el9_4, kernel-rt-modules-core 5.14.0-427.35.1.el9_4, kernel-rt-debug-modules 5.14.0-427.35.1.el9_4, +4 more
    fixed: vendor fix RHSA-2024:6567
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-24-102-01 updated cvss 5.5

Siemens SIMATIC S7-1500 TM MFP

  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 y ago

Exploit prediction

0.19% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux
  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.