{"id":"CVE-2026-31404","summary":"NFSD: Defer sub-object cleanup in export put callbacks","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Defer sub-object cleanup in export put callbacks\n\nsvc_export_put() calls path_put() and auth_domain_put() immediately\nwhen the last reference drops, before the RCU grace period. RCU\nreaders in e_show() and c_show() access both ex_path (via\nseq_path/d_path) and ex_client-\u003ename (via seq_escape) without\nholding a reference. If cache_clean removes the entry and drops the\nlast reference concurrently, the sub-objects are freed while still\nin use, producing a NULL pointer dereference in d_path.\n\nCommit 2530766492ec (\"nfsd: fix UAF when access ex_uuid or\nex_stats\") moved kfree of ex_uuid and ex_stats into the\ncall_rcu callback, but left path_put() and auth_domain_put() running\nbefore the grace period because both may sleep and call_rcu\ncallbacks execute in softirq context.\n\nReplace call_rcu/kfree_rcu with queue_rcu_work(), which defers the\ncallback until after the RCU grace period and executes it in process\ncontext where sleeping is permitted. This allows path_put() and\nauth_domain_put() to be moved into the deferred callback alongside\nthe other resource releases. Apply the same fix to expkey_put(),\nwhich has the identical pattern with ek_path and ek_client.\n\nA dedicated workqueue scopes the shutdown drain to only NFSD\nexport release work items; flushing the shared\nsystem_unbound_wq would stall on unrelated work from other\nsubsystems. nfsd_export_shutdown() uses rcu_barrier() followed\nby flush_workqueue() to ensure all deferred release callbacks\ncomplete before the export caches are destroyed.\n\nReviwed-by: Jeff Layton \u003cjlayton@kernel.org\u003e","modified":"2026-05-22T03:54:56.630994520Z","published":"2026-04-03T15:16:07.207Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31404.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2829e80d29b627886d12b5ea40856d56b516e67d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/48db892356d6cb80f6942885545de4a6dd8d2a29"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f5ab1bec5fa18731e0b1b1e60c9a68667ac73ea2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31404.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31404"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"c224edca7af028828e2ad866b61d731b5e72b46d"},{"fixed":"2829e80d29b627886d12b5ea40856d56b516e67d"},{"fixed":"f5ab1bec5fa18731e0b1b1e60c9a68667ac73ea2"},{"fixed":"48db892356d6cb80f6942885545de4a6dd8d2a29"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31404.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.14.0"},{"fixed":"6.18.20"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.10"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31404.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}