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CVE-2026-89662

NFSD: Prevent lock owner use-after-free during client teardown

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 4.10, 4.15, 4.16, 5.10.270, 5.15.221, and 5 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: total

Summary

In the Linux kernel, the following vulnerability has been resolved: NFSD: Prevent lock owner use-after-free during client teardown __destroy_client() releases a client's open owners, but a lock owner whose only reference is a blocked lock (nbl) stays on cl_ownerstr_hashtbl. client_has_state() does not count a bare owner, so DESTROY_CLIENTID can reach __destroy_client() with such owners present. __destroy_client() then walks the table, calling remove_blocked_locks() on each owner without a reference. Freeing a blocked lock drops the owner reference held via flc_owner. The per-net laundromat reaps blocked locks from nn->blocked_locks_lru independently of client state. The two paths share blocked_locks_lock only for the list splice, not the owner's lifetime. The laundromat therefore frees the owner as __destroy_client() dereferences it, a NULL dereference in remove_blocked_locks(). nfsd4_release_lockowner() holds a reference across the same call; __destroy_client() does not. Hold cl_lock across the walk, taking a reference and unhashing each owner, then drop it before remove_blocked_locks() and nfs4_put_stateowner(), which take blocked_locks_lock and cl_lock.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 68ef3bc3166468678d5e1fdd216628c35bd1186f · fixed in 42d7954b0a1907d4ef122aef94561952a033cdc3; From 68ef3bc3166468678d5e1fdd216628c35bd1186f · fixed in bb38ff8b4dafbbd1781ad37cd96722fdf2cd972a; From 68ef3bc3166468678d5e1fdd216628c35bd1186f · fixed in b8bad5a11416b26cc7fd4b18fba46d75ff636558; From 68ef3bc3166468678d5e1fdd216628c35bd1186f · fixed in 1ce74d1b7770e69735e8f8e509807af4ff9c8ee7; From 68ef3bc3166468678d5e1fdd216628c35bd1186f · fixed in a6ead6fff3a7d03e49845f048f7000a2e0d34431; From 68ef3bc3166468678d5e1fdd216628c35bd1186f · fixed in 4804c58f73a80d12df1de323bf97a164f6ee8743; From 68ef3bc3166468678d5e1fdd216628c35bd1186f · fixed in 8cf4ff0a7c083dd5e0067f517d63979b74b66649; From 68ef3bc3166468678d5e1fdd216628c35bd1186f · fixed in 5e2fa29d223a9a1e6a948e40b109d09081d1decd; From 4.9.91 · fixed in 4.10; From 4.14.31 · fixed in 4.15; From 4.15.14 · fixed in 4.16

  • Linux Linux

    4.16

  • KernelLinux

    From 4.16.0 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.109; From 6.13.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 8

git.kernel.org