{"id":"CVE-2026-89507","title":"RDMA/ucma: Lock the handler in ucma_write_cm_event()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/ucma: Lock the handler in ucma_write_cm_event()\n\nctx->file may only be changed under the handler lock and the xa_lock, which\nis what stops uevents being queued for…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","cwe":["CWE-367"],"vendor":"Linux","product":"Linux","affected":["Linux >= a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5 < 4f8bb11dd2ff365e7cff1c9964ab4607292d364e","Linux >= a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5 < 0be1955040a2eceed0ecfc387fdc92305411d273","Linux >= a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5 < f4cc21c6a8e9d392871477f9fd98d68e5ad80272","Linux 6.18"],"published":"2026-09-11","updated":"2026-10-19","sourceUpdated":"2026-10-19T08:47:58.674Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89507","references":[{"url":"https://git.kernel.org/stable/c/4f8bb11dd2ff365e7cff1c9964ab4607292d364e"},{"url":"https://git.kernel.org/stable/c/0be1955040a2eceed0ecfc387fdc92305411d273"},{"url":"https://git.kernel.org/stable/c/f4cc21c6a8e9d392871477f9fd98d68e5ad80272"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89507.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89507"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2532319"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89507"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89507"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89507.mbox"}],"tags":["cve.org","csaf","vex","red-hat","score-dispute"],"epss":0.00127,"epssPercentile":0.02375,"scores":{"cna":7.8,"vendor":5.5},"ingestedAt":"2026-09-14T15:23:07.475Z","slug":"CVE-2026-89507","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/ucma: Lock the handler in ucma_write_cm_event()\n\nctx->file may only be changed under the handler lock and the xa_lock, which\nis what stops uevents being queued for a ctx while ucma_migrate_id() moves\nit to another file.  The CM core takes that lock before invoking\nucma_event_handler(), but the write() paths that queue uevents themselves\ndo not.\n\nucma_write_cm_event() re-reads ctx->file for each of its four dereferences,\nso ucma_migrate_id() can swap it mid-sequence:\n\n\tmutex_lock(&ctx->file->mut);\t\t\t/* file A */\n\tlist_add_tail(&uevent->list, &ctx->file->event_list);\t/* file B */\n\tmutex_unlock(&ctx->file->mut);\t\t\t/* file B */\n\twake_up_interruptible(&ctx->file->poll_wait);\t/* file B */\n\nThe window is the mutex_lock() itself: the writer sleeps in it while the\nmigration reassigns ctx->file.  The list_add_tail() then runs on file B's\nevent_list holding only file A's mutex:\n\n  list_add corruption. prev->next should be next (ffff888101320f30),\n    but was ffff88814a08c418. (prev=ffff88814a075c18).\n  kernel BUG at lib/list_debug.c:32!\n  Call Trace:\n   ucma_write_cm_event+0x36e/0x5e0\n\nand file A's mut is left held forever, wedging its next writer in D state.\nThe uevent is also stranded on a list ucma_cleanup_ctx_events() will not\nwalk, so it outlives its context.  /dev/infiniband/rdma_cm is 0666 and no\nRDMA device is involved, so an unprivileged user reaches all of this.\n\nTake the handler lock, as ucma_cleanup_mc_events() does; ctx->cm_id is\npinned by the ucma_get_ctx() reference.\n\n## Affected\n\n- `Linux >= a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5 < 4f8bb11dd2ff365e7cff1c9964ab4607292d364e`\n- `Linux >= a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5 < 0be1955040a2eceed0ecfc387fdc92305411d273`\n- `Linux >= a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5 < f4cc21c6a8e9d392871477f9fd98d68e5ad80272`\n- `Linux 6.18`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat OpenShift Container Platform 4 · updated 2026-09-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89507.json)","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":224725,"id":"CVE-2026-89507","ts":1792401504699,"field":"cvss","old":"5.5","new":"7.8"},{"seq":224724,"id":"CVE-2026-89507","ts":1792401504699,"field":"severity","old":"medium","new":"high"},{"seq":205468,"id":"CVE-2026-89507","ts":1789576721355,"field":"cvss","old":"4.7","new":"5.5"},{"seq":203030,"id":"CVE-2026-89507","ts":1789403733418,"field":"cvss","old":"7.8","new":"4.7"},{"seq":203029,"id":"CVE-2026-89507","ts":1789403733418,"field":"severity","old":"high","new":"medium"},{"seq":198004,"id":"CVE-2026-89507","ts":1789384321336,"field":"cvss","old":"4.7","new":"7.8"},{"seq":198003,"id":"CVE-2026-89507","ts":1789384321336,"field":"severity","old":"medium","new":"high"},{"seq":183781,"id":"CVE-2026-89507","ts":1789356677361,"field":"cvss","old":"7.8","new":"4.7"},{"seq":183780,"id":"CVE-2026-89507","ts":1789356677361,"field":"severity","old":"high","new":"medium"},{"seq":153298,"id":"CVE-2026-89507","ts":1789285349937,"field":"cvss","old":null,"new":"7.8"},{"seq":153297,"id":"CVE-2026-89507","ts":1789285349937,"field":"severity","old":"none","new":"high"},{"seq":147391,"id":"CVE-2026-89507","ts":1789270210721,"field":"cvss","old":null,"new":"4.7"},{"seq":147390,"id":"CVE-2026-89507","ts":1789270210721,"field":"severity","old":"none","new":"medium"},{"seq":109139,"id":"CVE-2026-89507","ts":1789183730462,"field":"cvss","old":null,"new":"4.7"},{"seq":109138,"id":"CVE-2026-89507","ts":1789183730462,"field":"severity","old":"none","new":"medium"}]}