{"api_version":"1","generated_at":"2026-09-12T12:04:56+00:00","cve":"CVE-2026-89670","urls":{"html":"https://cve.report/CVE-2026-89670","api":"https://cve.report/api/cve/CVE-2026-89670.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-89670","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-89670"},"summary":{"title":"nfsd: hold rcu across localio cmpxchg retry","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: hold rcu across localio cmpxchg retry\n\nnfsd_file objects are freed via call_rcu (filecache.c:296), and\nnfsd_file_slab is created without SLAB_TYPESAFE_BY_RCU\n(KMEM_CACHE(nfsd_file, 0) at filecache.c:789), so the slab page\nbacking a freed nfsd_file becomes freely reclaimable once the RCU\ngrace period elapses.\n\nThe again: retry block in nfsd_open_local_fh() loads a pointer with\ncmpxchg and then calls nfsd_file_get(new) (which is\nrefcount_inc_not_zero) without holding rcu_read_lock. The sole caller\nnfs_open_local_fh() drops rcu_read_lock before invoking this helper,\nso no outer reader-side critical section covers the load.\n\n    CPU 0 (nfsd_open_local_fh)        CPU 1 (nfsd_file_put_local)\n    -----                             -----\n    new = cmpxchg(pnf, NULL, ...)\n                                      nf = xchg(pnf, NULL)\n                                      nfsd_file_put(nf)\n                                        last ref -> call_rcu()\n                                      /* grace period elapses;\n                                         slab page recycled */\n    nfsd_file_get(new)\n      refcount_inc_not_zero(&new->nf_ref)\n      /* operates on recycled memory */\n\nA non-zero word at the nf_ref offset of the recycled object makes the\nrefcount bump appear to succeed, and the caller then dereferences\nnew->nf_net and new->nf_file out of freed memory.\n\nFix by taking rcu_read_lock() immediately before the cmpxchg and\nreleasing it on all three exits of the if (new) block: the goto-again\nretry, the lost-race cleanup path, and the install-succeeded path.\nnfsd_file_put() and nfsd_net_put() stay outside the RCU section so\nthey remain free to block.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-11 20:19:53","updated_at":"2026-09-11 20:19:53"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/559570f91a7d4d199a72105e4980bef791f4cbf1","name":"https://git.kernel.org/stable/c/559570f91a7d4d199a72105e4980bef791f4cbf1","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/763c0bad872368304db718f79af7e93048885c67","name":"https://git.kernel.org/stable/c/763c0bad872368304db718f79af7e93048885c67","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/58884694978a3d7d111edb433d7fd6a6c5af2f34","name":"https://git.kernel.org/stable/c/58884694978a3d7d111edb433d7fd6a6c5af2f34","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89670","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89670","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected e6f7e1487ab528a6c653bd0d42812ff2942846cd 763c0bad872368304db718f79af7e93048885c67 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected e6f7e1487ab528a6c653bd0d42812ff2942846cd 559570f91a7d4d199a72105e4980bef791f4cbf1 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected e6f7e1487ab528a6c653bd0d42812ff2942846cd 58884694978a3d7d111edb433d7fd6a6c5af2f34 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 986a21ace186433e0397a59491646edad8c8d636 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.15.3 6.16 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.16","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.16 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.50 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.4 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/nfsd/localio.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"763c0bad872368304db718f79af7e93048885c67","status":"affected","version":"e6f7e1487ab528a6c653bd0d42812ff2942846cd","versionType":"git"},{"lessThan":"559570f91a7d4d199a72105e4980bef791f4cbf1","status":"affected","version":"e6f7e1487ab528a6c653bd0d42812ff2942846cd","versionType":"git"},{"lessThan":"58884694978a3d7d111edb433d7fd6a6c5af2f34","status":"affected","version":"e6f7e1487ab528a6c653bd0d42812ff2942846cd","versionType":"git"},{"status":"affected","version":"986a21ace186433e0397a59491646edad8c8d636","versionType":"git"},{"lessThan":"6.16","status":"affected","version":"6.15.3","versionType":"semver"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/nfsd/localio.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.16"},{"lessThan":"6.16","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.50","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.4","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.50","versionStartIncluding":"6.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.4","versionStartIncluding":"6.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"6.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15.3","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: hold rcu across localio cmpxchg retry\n\nnfsd_file objects are freed via call_rcu (filecache.c:296), and\nnfsd_file_slab is created without SLAB_TYPESAFE_BY_RCU\n(KMEM_CACHE(nfsd_file, 0) at filecache.c:789), so the slab page\nbacking a freed nfsd_file becomes freely reclaimable once the RCU\ngrace period elapses.\n\nThe again: retry block in nfsd_open_local_fh() loads a pointer with\ncmpxchg and then calls nfsd_file_get(new) (which is\nrefcount_inc_not_zero) without holding rcu_read_lock. The sole caller\nnfs_open_local_fh() drops rcu_read_lock before invoking this helper,\nso no outer reader-side critical section covers the load.\n\n    CPU 0 (nfsd_open_local_fh)        CPU 1 (nfsd_file_put_local)\n    -----                             -----\n    new = cmpxchg(pnf, NULL, ...)\n                                      nf = xchg(pnf, NULL)\n                                      nfsd_file_put(nf)\n                                        last ref -> call_rcu()\n                                      /* grace period elapses;\n                                         slab page recycled */\n    nfsd_file_get(new)\n      refcount_inc_not_zero(&new->nf_ref)\n      /* operates on recycled memory */\n\nA non-zero word at the nf_ref offset of the recycled object makes the\nrefcount bump appear to succeed, and the caller then dereferences\nnew->nf_net and new->nf_file out of freed memory.\n\nFix by taking rcu_read_lock() immediately before the cmpxchg and\nreleasing it on all three exits of the if (new) block: the goto-again\nretry, the lost-race cleanup path, and the install-succeeded path.\nnfsd_file_put() and nfsd_net_put() stay outside the RCU section so\nthey remain free to block."}],"providerMetadata":{"dateUpdated":"2026-09-11T19:45:55.846Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/763c0bad872368304db718f79af7e93048885c67"},{"url":"https://git.kernel.org/stable/c/559570f91a7d4d199a72105e4980bef791f4cbf1"},{"url":"https://git.kernel.org/stable/c/58884694978a3d7d111edb433d7fd6a6c5af2f34"}],"title":"nfsd: hold rcu across localio cmpxchg retry","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-89670","datePublished":"2026-09-11T19:45:55.846Z","dateReserved":"2026-09-11T19:38:34.746Z","dateUpdated":"2026-09-11T19:45:55.846Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-11 20:19:53","lastModifiedDate":"2026-09-11 20:19:53","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"89670","Ordinal":"1","Title":"nfsd: hold rcu across localio cmpxchg retry","CVE":"CVE-2026-89670","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"89670","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: hold rcu across localio cmpxchg retry\n\nnfsd_file objects are freed via call_rcu (filecache.c:296), and\nnfsd_file_slab is created without SLAB_TYPESAFE_BY_RCU\n(KMEM_CACHE(nfsd_file, 0) at filecache.c:789), so the slab page\nbacking a freed nfsd_file becomes freely reclaimable once the RCU\ngrace period elapses.\n\nThe again: retry block in nfsd_open_local_fh() loads a pointer with\ncmpxchg and then calls nfsd_file_get(new) (which is\nrefcount_inc_not_zero) without holding rcu_read_lock. The sole caller\nnfs_open_local_fh() drops rcu_read_lock before invoking this helper,\nso no outer reader-side critical section covers the load.\n\n    CPU 0 (nfsd_open_local_fh)        CPU 1 (nfsd_file_put_local)\n    -----                             -----\n    new = cmpxchg(pnf, NULL, ...)\n                                      nf = xchg(pnf, NULL)\n                                      nfsd_file_put(nf)\n                                        last ref -> call_rcu()\n                                      /* grace period elapses;\n                                         slab page recycled */\n    nfsd_file_get(new)\n      refcount_inc_not_zero(&new->nf_ref)\n      /* operates on recycled memory */\n\nA non-zero word at the nf_ref offset of the recycled object makes the\nrefcount bump appear to succeed, and the caller then dereferences\nnew->nf_net and new->nf_file out of freed memory.\n\nFix by taking rcu_read_lock() immediately before the cmpxchg and\nreleasing it on all three exits of the if (new) block: the goto-again\nretry, the lost-race cleanup path, and the install-succeeded path.\nnfsd_file_put() and nfsd_net_put() stay outside the RCU section so\nthey remain free to block.","Type":"Description","Title":"nfsd: hold rcu across localio cmpxchg retry"}]}}}