CVE-2026-89507 (GCVE-0-2026-89507)
Vulnerability from cvelistv5
Published
2026-09-11 19:43
Modified
2026-10-19 08:47
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: RDMA/ucma: Lock the handler in ucma_write_cm_event() ctx->file may only be changed under the handler lock and the xa_lock, which is what stops uevents being queued for a ctx while ucma_migrate_id() moves it to another file. The CM core takes that lock before invoking ucma_event_handler(), but the write() paths that queue uevents themselves do not. ucma_write_cm_event() re-reads ctx->file for each of its four dereferences, so ucma_migrate_id() can swap it mid-sequence: mutex_lock(&ctx->file->mut); /* file A */ list_add_tail(&uevent->list, &ctx->file->event_list); /* file B */ mutex_unlock(&ctx->file->mut); /* file B */ wake_up_interruptible(&ctx->file->poll_wait); /* file B */ The window is the mutex_lock() itself: the writer sleeps in it while the migration reassigns ctx->file. The list_add_tail() then runs on file B's event_list holding only file A's mutex: list_add corruption. prev->next should be next (ffff888101320f30), but was ffff88814a08c418. (prev=ffff88814a075c18). kernel BUG at lib/list_debug.c:32! Call Trace: ucma_write_cm_event+0x36e/0x5e0 and file A's mut is left held forever, wedging its next writer in D state. The uevent is also stranded on a list ucma_cleanup_ctx_events() will not walk, so it outlives its context. /dev/infiniband/rdma_cm is 0666 and no RDMA device is involved, so an unprivileged user reaches all of this. Take the handler lock, as ucma_cleanup_mc_events() does; ctx->cm_id is pinned by the ucma_get_ctx() reference.
References
Impacted products
Vendor Product Version
Linux Linux Version: a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5
Version: a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5
Version: a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/infiniband/core/ucma.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "4f8bb11dd2ff365e7cff1c9964ab4607292d364e",
              "status": "affected",
              "version": "a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5",
              "versionType": "git"
            },
            {
              "lessThan": "0be1955040a2eceed0ecfc387fdc92305411d273",
              "status": "affected",
              "version": "a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5",
              "versionType": "git"
            },
            {
              "lessThan": "f4cc21c6a8e9d392871477f9fd98d68e5ad80272",
              "status": "affected",
              "version": "a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/infiniband/core/ucma.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.18"
            },
            {
              "lessThan": "6.18",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "6.18",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/ucma: Lock the handler in ucma_write_cm_event()\n\nctx-\u003efile 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-\u003efile for each of its four dereferences,\nso ucma_migrate_id() can swap it mid-sequence:\n\n\tmutex_lock(\u0026ctx-\u003efile-\u003emut);\t\t\t/* file A */\n\tlist_add_tail(\u0026uevent-\u003elist, \u0026ctx-\u003efile-\u003eevent_list);\t/* file B */\n\tmutex_unlock(\u0026ctx-\u003efile-\u003emut);\t\t\t/* file B */\n\twake_up_interruptible(\u0026ctx-\u003efile-\u003epoll_wait);\t/* file B */\n\nThe window is the mutex_lock() itself: the writer sleeps in it while the\nmigration reassigns ctx-\u003efile.  The list_add_tail() then runs on file B\u0027s\nevent_list holding only file A\u0027s mutex:\n\n  list_add corruption. prev-\u003enext 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\u0027s 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-\u003ecm_id is\npinned by the ucma_get_ctx() reference."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Reached by write() on the local misc device /dev/infiniband/rdma_cm (ucma_write \u2192 WRITE_CM_EVENT racing MIGRATE_ID). Remote RDMA CM packet handling already takes the handler lock in ucma_event_handler(), so this bug is not a network-packet path.\nAC:L - The attacker fully controls both sides of the race: one thread issues WRITE_CM_EVENT while another issues MIGRATE_ID on the same ctx, and can hold file A\u0027s mutex from a third thread so the writer sleeps in mutex_lock() across ctx-\u003efile reassignment.\nPR:L - ucma registers /dev/infiniband/rdma_cm with mode 0666 and the command path (create_id, write_cm_event, migrate_id) has no capability checks. No RDMA hardware is required (ucma_get_ctx, not ucma_get_ctx_dev), so any unprivileged local user can open the device and trigger the bug.\nUI:N - Exploitation uses only the attacker\u0027s own open/write syscalls against rdma_cm; no other user or administrator action is required.\nS:U - This is in-kernel list corruption and use-after-free within the host kernel\u0027s security authority. It can escalate privileges on the host but does not cross a VM, IOMMU, or sandbox boundary.\nC:H - The unlocked list_add can strand a uevent on another file\u0027s list so it outlives its ucma_context, and concurrent GET_EVENT can free a ucma_event still being linked (UAF). Per UAF guidance that enables attacker-controlled reuse and arbitrary kernel reads.\nI:H - list_add_tail on file B\u0027s event_list while holding only file A\u0027s mutex, plus mutex_unlock of an unheld mutex, corrupts kernel lists; combined with UAF of ctx/uevent this yields heap-sprayable write and list-unlink primitives for control-flow hijacking.\nA:H - The race was reproduced as kernel BUG at lib/list_debug.c:32 in ucma_write_cm_event, and file A\u0027s mutex is left held forever wedging later writers in D-state. UAFs also oops, so availability impact is high even without full exploitation."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:47:58.674Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "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"
        }
      ],
      "title": "RDMA/ucma: Lock the handler in ucma_write_cm_event()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89507",
    "datePublished": "2026-09-11T19:43:54.013Z",
    "dateReserved": "2026-09-11T19:38:34.716Z",
    "dateUpdated": "2026-10-19T08:47:58.674Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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