nfsd: fix RELEASE_LOCKOWNER

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Summary

CVECVE-2024-26629
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-03-13 14:15:07 UTC
Updated2026-05-12 12:16:18 UTC
DescriptionIn 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'.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-667

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected ef481b262bba4f454351eec43f024fec942c2d4c 10d75984495f7fe62152c3b0dbfa3f0a6b739c9b git Not specified
CNA Linux Linux affected 3097f38e91266c7132c3fdb7e778fac858c00670 99fb654d01dc3f08b5905c663ad6c89a9d83302f git Not specified
CNA Linux Linux affected e2fc17fcc503cfca57b5d1dd3b646ca7eebead97 c6f8b3fcc62725e4129f2c0fd550d022d4a7685a git Not specified
CNA Linux Linux affected ce3c4ad7f4ce5db7b4f08a1e237d8dd94b39180b e4cf8941664cae2f89f0189c29fe2ce8c6be0d03 git Not specified
CNA Linux Linux affected ce3c4ad7f4ce5db7b4f08a1e237d8dd94b39180b b7d2eee1f53899b53f069bba3a59a419fc3d331b git Not specified
CNA Linux Linux affected ce3c4ad7f4ce5db7b4f08a1e237d8dd94b39180b 8f5b860de87039b007e84a28a5eefc888154e098 git Not specified
CNA Linux Linux affected ce3c4ad7f4ce5db7b4f08a1e237d8dd94b39180b edcf9725150e42beeca42d085149f4c88fa97afd git Not specified
CNA Linux Linux affected fea1d0940301378206955264a01778700fc9c16f git Not specified
CNA Linux Linux affected 2ec65dc6635d1976bd1dbf2640ff7f810b2f6dd1 git Not specified
CNA Linux Linux affected a2235bc65ade40982c3d09025cdd34bc539d6a69 git Not specified
CNA Linux Linux affected ba747abfca27e23c42ded3912c87b70d7e16b6ab git Not specified
CNA Linux Linux affected e8020d96dd5b2dcc1f6a8ee4f87a53a373002cd5 git Not specified
CNA Linux Linux affected 5.19 Not specified
CNA Linux Linux unaffected 5.19 semver Not specified
CNA Linux Linux unaffected 4.19.306 4.19.* semver Not specified
CNA Linux Linux unaffected 5.10.220 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.154 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.79 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.15 6.6.* semver Not specified
CNA Linux Linux unaffected 6.7.3 6.7.* semver Not specified
CNA Linux Linux unaffected 6.8 * original_commit_for_fix Not specified
ADP Siemens SIMATIC S7-1500 TM MFP - GNU/Linux Subsystem affected * custom Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/8f5b860de87039b007e84a28a5eefc888154e098 af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Mailing List, Patch
git.kernel.org/stable/c/10d75984495f7fe62152c3b0dbfa3f0a6b739c9b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
cert-portal.siemens.com/productcert/html/ssa-265688.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/b7d2eee1f53899b53f069bba3a59a419fc3d331b af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Mailing List, Patch
git.kernel.org/stable/c/e4cf8941664cae2f89f0189c29fe2ce8c6be0d03 af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Mailing List, Patch
git.kernel.org/stable/c/c6f8b3fcc62725e4129f2c0fd550d022d4a7685a af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Mailing List, Patch
git.kernel.org/stable/c/99fb654d01dc3f08b5905c663ad6c89a9d83302f af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Mailing List, Patch
git.kernel.org/stable/c/edcf9725150e42beeca42d085149f4c88fa97afd af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Mailing List, Patch
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Legacy QID Mappings

  • 6000567 Debian Security Update for linux (DSA 5658-1)
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