{"id":"CVE-2026-89655","revision":"06cd96c476a74c1e8ce53fdc881c2001","records":[{"revision":"06cd96c476a74c1e8ce53fdc881c2001","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-89655","aliases":[],"title":"ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock\n\nlist_for_each_entry() iterates ci->i_cap_flush_list but drops\ni_ceph_lock to send cap messages.  During the unlock window,\nhandle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries\nwith tid <= flush_tid from the list, release i_ceph_lock, and free\nthem via ceph_free_cap_flush() outside any lock.  When the original\nthread reacquires i_ceph_lock and the for-loop macro advances via\ncf = list_next_entry(cf, i_list), it dereferences cf->i_list.next\non freed memory.\n\nThe race timeline:\n\n  __kick_flushing_caps()              handle_cap_flush_ack()\n  -----------------------             -----------------------\n  holds i_ceph_lock        <---\n  iterates to cf (tid=10)\n  prepares FLUSH message\n  drops i_ceph_lock        <---\n  __send_cap() ── FLUSH(tid=10)\n\t                              MDS sends FLUSH_ACK(tid=10)\n                           --->       acquires i_ceph_lock\n                                      cf->tid(10) <= flush_tid(10),\n                                      detaches cf from i_cap_flush_list\n                                      drops i_ceph_lock\n                                      ceph_free_cap_flush(cf) <- frees it!\n  acquires i_ceph_lock     <---\n  for-loop advances:\n    cf = list_next_entry(cf, i_list)\n      -- UAF on freed cf->i_list.next\n\nThe cf was just sent by __kick_flushing_caps itself via __send_cap().\nThe MDS may respond with FLUSH_ACK quickly enough that\nhandle_cap_flush_ack() frees cf before __kick_flushing_caps can\nfinish the iteration.\n\nFix by converting to a manual while loop: save the next pointer\nunder i_ceph_lock before dropping it, then use the saved pointer\nafter reacquiring, so the potentially-freed cf is never accessed again.","state":0,"publishedAt":"2026-09-11T19:45:44.841+00:00","modifiedAt":"2026-10-19T08:50:26.879+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"fs/ceph/caps.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"e4500b5e35c213e0f97be7cb69328c0877203a79\",\n                            \"lessThan\": \"091137821e1fc88f37e15201abf055c9494ddc61\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"e4500b5e35c213e0f97be7cb69328c0877203a79\",\n                            \"lessThan\": \"01542430081014d80fc9e70e92d6647432ddb7fc\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"e4500b5e35c213e0f97be7cb69328c0877203a79\",\n                            \"lessThan\": \"23eb34a53a53cb1a6dab1eeee830633207ac158d\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"e4500b5e35c213e0f97be7cb69328c0877203a79\",\n                            \"lessThan\": \"19f16f04c2b014a7dd214dc1e42557d8530b16f3\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"e4500b5e35c213e0f97be7cb69328c0877203a79\",\n                            \"lessThan\": \"2701431aa3cc8b23efe6890182e7b04f5e76fab5\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"e4500b5e35c213e0f97be7cb69328c0877203a79\",\n                            \"lessThan\": \"fe46746087b5b9c5bb2d022df6c7819218494ced\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"e4500b5e35c213e0f97be7cb69328c0877203a79\",\n                            \"lessThan\": \"2dba24dcd5050be4b7b119e6f0b01f62203b5d26\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"e4500b5e35c213e0f97be7cb69328c0877203a79\",\n                            \"lessThan\": \"7af4c4f01305b0935adf6d4301b1ec407025485d\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"fs/ceph/caps.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"4.8\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"4.8\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.270\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.221\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.188\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.157\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.109\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.50\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.4\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8,"severity":"CRITICAL"}],"references":["https://git.kernel.org/stable/c/091137821e1fc88f37e15201abf055c9494ddc61","https://git.kernel.org/stable/c/01542430081014d80fc9e70e92d6647432ddb7fc","https://git.kernel.org/stable/c/23eb34a53a53cb1a6dab1eeee830633207ac158d","https://git.kernel.org/stable/c/19f16f04c2b014a7dd214dc1e42557d8530b16f3","https://git.kernel.org/stable/c/2701431aa3cc8b23efe6890182e7b04f5e76fab5","https://git.kernel.org/stable/c/fe46746087b5b9c5bb2d022df6c7819218494ced","https://git.kernel.org/stable/c/2dba24dcd5050be4b7b119e6f0b01f62203b5d26","https://git.kernel.org/stable/c/7af4c4f01305b0935adf6d4301b1ec407025485d"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89655","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-89655","identifiers":["CVE-2026-89655"]},"retained":false,"historicalAffected":[]}],"coverage":[]}