{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89507", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.716Z", "datePublished": "2026-09-11T19:43:54.013Z", "dateUpdated": "2026-10-19T08:47:58.674Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:47:58.674Z" }, "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->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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Reached by write() on the local misc device /dev/infiniband/rdma_cm (ucma_write → 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's mutex from a third thread so the writer sleeps in mutex_lock() across ctx->file 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's 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's 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's 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's event_list while holding only file A's 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's mutex is left held forever wedging later writers in D-state. UAFs also oops, so availability impact is high even without full exploitation." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/infiniband/core/ucma.c" ], "versions": [ { "version": "a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5", "lessThan": "4f8bb11dd2ff365e7cff1c9964ab4607292d364e", "status": "affected", "versionType": "git" }, { "version": "a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5", "lessThan": "0be1955040a2eceed0ecfc387fdc92305411d273", "status": "affected", "versionType": "git" }, { "version": "a3c9d0fcd3715541bbf97da2ddde9d032e2fe6d5", "lessThan": "f4cc21c6a8e9d392871477f9fd98d68e5ad80272", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/infiniband/core/ucma.c" ], "versions": [ { "version": "6.18", "status": "affected" }, { "version": "0", "lessThan": "6.18", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.50", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18", "versionEndExcluding": "7.3" } ] } ] } ], "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" } } } }