{"id":"CVE-2026-89495","summary":"ocfs2: bound namelen in dlm_migrate_request_handler","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nocfs2: bound namelen in dlm_migrate_request_handler\n\nPatch series \"ocfs2/dlm: bound peer-controlled lengths in the o2dlm\".\n\nThe o2dlm receive handlers trust u8 length and count fields from the wire\nwithout bounding them, so a node in a DLM domain can corrupt or panic any\nother node with a malformed message.  Three defects:\n\n  - dlm_migrate_request_handler() passes migrate-\u003enamelen unchecked to\n    dlm_init_mle(), which memcpy()s it into the 32-byte mname[] of an\n    o2dlm_mle slab object: a heap out-of-bounds write of up to ~215\n    attacker-controlled bytes.\n\n  - dlm_mig_lockres_handler() passes mres-\u003elockname_len unchecked to\n    dlm_init_lockres(), which memcpy()s it into the 32-byte o2dlm_lockname\n    slab object: a heap out-of-bounds write of up to ~223 bytes.\n\n  - the same handler trusts mres-\u003enum_locks without checking that the\n    message is large enough to hold that many entries, so\n    dlm_process_recovery_data() walks mres-\u003eml[] past the kmalloc(data_len)\n    copy and trips a BUG_ON (an out-of-bounds read ending in a panic).\n\nThe other o2dlm receive handlers already reject an oversized name; the\nmigration and recovery handlers have omitted it since the DLM was added\n(see the Fixes tags).  Patch 1 bounds namelen; patch 2 validates\nlockname_len, num_locks, and the payload size.  Conforming recovery and\nmigration traffic is unaffected.\n\no2net authenticates peers only by the DLM domain key, so any node that has\njoined the domain -- including a compromised or malicious member -- can\nsend these messages.  There is no local trigger; the attacker must already\nbe a member of the cluster.\n\nEach sink was confirmed under KASAN with an out-of-tree module mirroring\nit exactly -- a kmem_cache/kmalloc of the real destination size, then the\nsame unclamped memcpy/loop: slab-out-of-bounds Write for the two writes,\nRead for the recovery walk, and a panic.  A userspace AddressSanitizer\nbuild faults identically under -m32 and -m64.  Scrubbed logs are available\non request.\n\nI reported this privately to security@kernel.org and the ocfs2 maintainers\non 2026-06-20; with no response after the standard embargo period I am\nposting the fix publicly.  I have no embargo requirement.\n\n\nThis patch (of 2):\n\nA node receiving a DLM_MIGRATE_REQUEST message trusts the peer-supplied\nname length (migrate-\u003enamelen) without bounding it.  dlm_init_mle() then\ncopies that many bytes into the fixed DLM_LOCKID_NAME_MAX-byte mname[]\narray of an o2dlm_mle slab object, so a malformed message from a cluster\npeer overflows the slab object by up to ~215 bytes: a heap out-of-bounds\nwrite of attacker-controlled data, reachable by any node in the domain.\n\nReject an oversized name, the way dlm_master_request_handler() and the\nother o2dlm receive handlers already do; the migration handler omits the\ncheck entirely.  Conforming messages are unaffected.","modified":"2026-09-13T03:47:18.585147422Z","published":"2026-09-11T19:43:46.107Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89495.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2487bea2098322669f0563baff53e797486b823f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/de10cd3b062a5235af754925fcf49beb5a1109d4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ea5b5609305a8437bc955a0834a530c12246d78f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f8658ee3327f73bd81c0bcd07cdeb5a8527fac98"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89495.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89495"},{"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":"6714d8e86bf443f6f7af50f9d432025649f091f5"},{"fixed":"f8658ee3327f73bd81c0bcd07cdeb5a8527fac98"},{"fixed":"de10cd3b062a5235af754925fcf49beb5a1109d4"},{"fixed":"2487bea2098322669f0563baff53e797486b823f"},{"fixed":"ea5b5609305a8437bc955a0834a530c12246d78f"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89495.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.6.16"},{"fixed":"6.12.109"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.50"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89495.json"}}],"schema_version":"1.9.0"}