NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-89712
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:19:58 UTC
Updated2026-09-11 20:19:58 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock nfsd4_ssc_expire_umount() walks nn->nfsd_ssc_mount_list with list_for_each_entry_safe(ni, tmp, ...). For each expired entry it sets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the source vfsmount, then reacquires the lock to list_del + kfree the entry and continue iterating via the macro's saved tmp pointer. The nsui_busy flag protects the current ni from concurrent nfsd4_ssc_setup_dul() finders during the lock-drop window, but it does not pin tmp. Another nfsd RPC thread that fails its source- server mount and reaches nfsd4_ssc_cancel_dul() will, during that same window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount item, and release the lock. If that item is the saved tmp of the expire walk, the next iteration dereferences a freed nfsd4_ssc_umount_item. Restart the walk from the head after the mntput() unlock window so no saved next pointer survives the lock-drop. The list is bounded by the number of active inter-server source mounts (typically small) and the expire delayed-work runs periodically rather than per-IO, so the restart is cheap.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected f4e44b393389c77958f7c58bf4415032b4cda15b 77de363d9a1c8cd35f20482782c612cda085791a git Not specified
CNA Linux Linux affected f4e44b393389c77958f7c58bf4415032b4cda15b 4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8 git Not specified
CNA Linux Linux affected f4e44b393389c77958f7c58bf4415032b4cda15b 7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9 git Not specified
CNA Linux Linux affected f4e44b393389c77958f7c58bf4415032b4cda15b 036c1b182f4da65363e79ec0ac276edc6b7296e5 git Not specified
CNA Linux Linux affected a4bc287943f5695209ff36bdc89f17b48d68fae7 git Not specified
CNA Linux Linux affected 5.10.220 5.11 semver Not specified
CNA Linux Linux affected 5.14 Not specified
CNA Linux Linux unaffected 5.14 semver Not specified
CNA Linux Linux unaffected 6.12.109 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.50 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/036c1b182f4da65363e79ec0ac276edc6b7296e5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/77de363d9a1c8cd35f20482782c612cda085791a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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