{"id":"CVE-2026-89654","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-89654","summary":"ceph: fix UAF in check_new_map() on session freed during unlock","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nceph: fix UAF in check_new_map() on session freed during unlock\n\ncheck_new_map() iterates mdsc->sessions[] and for each active session\ndrops mdsc->mutex to perform per-session operations.  The forced-close\npath (rank removed from map) correctly takes a reference on s via\nceph_get_mds_session() before releasing mdsc->mutex, but three other\npaths do not:\n\n  Path A (address changed):  mutex_unlock → mutex_lock(&s->s_mutex)\n  Path B (reconnect):        mutex_unlock → send_mds_reconnect(mdsc, s)\n  Path C (active transition): mutex_unlock → mutex_lock(&s->s_mutex)\n\nWithout the extra reference, another thread can acquire mdsc->mutex\nduring the unlock window, call __unregister_session() which drops the\nlast reference on s, and free it.  The original thread then accesses\nfreed memory via s->s_mutex.\n\nFix by adding ceph_get_mds_session(s) before each mutex_unlock and\nceph_put_mds_session(s) after the corresponding mutex_lock, matching\nthe pattern already used in the forced-close path.\n\nRace timeline (Path A):\n\n  Thread A (check_new_map)             Thread B (another map update\n    holds mdsc->mutex                      or session teardown)\n  --------------------------           --------------------------\n  s = mdsc->sessions[i]\n  (refcount == 1, held only by\n   sessions[] array)\n\n  mutex_unlock(&mdsc->mutex)\n                               --->    acquires mdsc->mutex\n                                       __unregister_session(mdsc, s)\n                                         sessions[i] = NULL\n                                         ceph_put_mds_session(s)\n                                           refcount: 1 -> 0\n                                           kfree(s)  <--- freed!\n\n  mutex_lock(&s->s_mutex)\n  UAF on freed s->s_mutex","published":"2026-09-11T19:45:44.086Z","modified":"2026-09-14T03:46:22.037035696Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"7.2.4"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/21d5be092d947f8d83f76f7ebf3989e7e9230a98"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ee611a7509554c4ca1f54f6aefe592fb1df7ea70"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89654.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89654"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-14T03:46:22.037035696Z"}}