{"id":"CVE-2026-64525","summary":"xfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit\n\nThe struct pernet_operations docstring in include/net/net_namespace.h\nexplicitly warns against blocking RCU primitives in .exit handlers:\n\n    Exit methods using blocking RCU primitives, such as\n    synchronize_rcu(), should be implemented via exit_batch.\n    [...]\n    Please, avoid synchronize_rcu() at all, where it's possible.\n\n    Note that a combination of pre_exit() and exit() can\n    be used, since a synchronize_rcu() is guaranteed between\n    the calls.\n\nxfrm_policy_fini() violates this: it calls synchronize_rcu() before\nfreeing the policy_bydst hash tables (so no RCU reader is mid-\ntraversal at free time), but runs from xfrm_net_ops.exit -- once per\nnamespace -- so a cleanup_net() of N namespaces pays N full RCU\ngrace periods serially.\n\nUse the documented pre_exit/exit split. Move the policy flush (and\nthe workqueue drains it depends on) into a new .pre_exit handler;\nxfrm_policy_fini() then runs in .exit and frees the hash tables\nafter the synchronize_rcu_expedited() that cleanup_net() guarantees\nbetween the two phases. Providing O(1) RCU grace periods per batch\ninstead of O(N).\n\nObserved on Linux 6.18 with a workload doing unshare(CLONE_NEWNET)\nat ~13/sec sustained: cleanup_net() and the netns_wq rescuer kthread\nboth stuck in xfrm_policy_fini()'s synchronize_rcu(), \u003e300k struct\nnet accumulated in the cleanup queue, Percpu in /proc/meminfo climbed\nto 130+ GB on 256-CPU hosts, and memcg OOMs followed. setup_net and\n__put_net counts were balanced, ruling out a refcount leak.","modified":"2026-10-08T02:51:31.402477027Z","published":"2026-07-25T09:20:49.256Z","related":["SUSE-SU-2026:23881-1","SUSE-SU-2026:23887-1","SUSE-SU-2026:23897-1","SUSE-SU-2026:23902-1","openSUSE-SU-2026:21910-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64525.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/3e52417318473782012b236d0325bf7d2266a597"},{"type":"WEB","url":"https://git.kernel.org/stable/c/91cc13978ab0bc6f669139f53e7e613a860d10e0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bca6386dc08750fc7cdcbc7683473748ba3114b9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d14ae8ef88c2c6590e107db61b6adce148cec7b3"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64525.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64525"},{"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":"438b1f668ad58f46ce699bb48e4698a7839e3f9e"},{"fixed":"bca6386dc08750fc7cdcbc7683473748ba3114b9"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3733fce2871c9bca9dd18a1a23b1432ea215a094"},{"fixed":"91cc13978ab0bc6f669139f53e7e613a860d10e0"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"069daad4f2ae9c5c108131995529d5f02392c446"},{"fixed":"d14ae8ef88c2c6590e107db61b6adce148cec7b3"},{"fixed":"3e52417318473782012b236d0325bf7d2266a597"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.12.83"},{"fixed":"6.12.93"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.18.24"},{"fixed":"6.18.35"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.6.136"},{"fixed":"6.7"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.19.14"},{"fixed":"6.20"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"b66920a3348c0f63ba18365248fa21fbf0b3a937"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"33a3149dd81a1e2f52b80ee1e0fc380b39f3d028"}]}],"versions":["v6.12.92","v6.12.91","v6.12.90","v6.12.89","v6.12.88","v6.12.87","v6.12.86","v6.12.85","v6.12.84","v6.12.83","v6.18.34","v6.18.33","v6.18.32","v6.18.31","v6.18.30","v6.18.29","v6.18.28","v6.18.27","v6.18.26","v6.18.25","v6.18.24","v6.6.158","v6.6.157","v6.6.156","v6.6.155","v6.6.154","v6.6.153","v6.6.152","v6.6.151","v6.6.150","v6.6.149","v6.6.148","v6.6.147","v6.6.146","v6.6.145","v6.6.144","v6.6.143","v6.6.142","v6.6.141","v6.6.140","v6.6.139","v6.6.138","v6.6.137","v6.6.136","v6.19.14"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64525.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.93"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.35"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.12"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64525.json"}}],"schema_version":"1.9.0"}