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CVE-2026-89712

NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
None on Exploit-DB, Metasploit or GitHub

Summary

In 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.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From a4bc287943f5695209ff36bdc89f17b48d68fae7 · fixed in 2b59029b8f24a99b5d844af2da3950d39d36eeea; From f4e44b393389c77958f7c58bf4415032b4cda15b · fixed in d9e151fea5ed706c1284adacabd869b0be745db2; From f4e44b393389c77958f7c58bf4415032b4cda15b · fixed in 659ee3da073164e1e6e40dfcbc26eeed85845f93; From f4e44b393389c77958f7c58bf4415032b4cda15b · fixed in 60680ae7243b22de3d09be990d8e23bcfc4af837; From f4e44b393389c77958f7c58bf4415032b4cda15b · fixed in 77de363d9a1c8cd35f20482782c612cda085791a; From f4e44b393389c77958f7c58bf4415032b4cda15b · fixed in 4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8; From f4e44b393389c77958f7c58bf4415032b4cda15b · fixed in 7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9; From f4e44b393389c77958f7c58bf4415032b4cda15b · fixed in 036c1b182f4da65363e79ec0ac276edc6b7296e5; From 5.10.220 · fixed in 5.10.270

  • Linux Linux

    5.14

  • KernelLinux

    fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.14.0 · fixed in 6.1.188; From 5.16.0 · fixed in 6.6.157; From 6.2.0 · fixed in 6.12.109; From 6.7.0 · fixed in 6.18.50; From 6.13.0 · fixed in 7.2.4

References 8

git.kernel.org