{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2024-39508", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-06-25T14:23:23.753Z", "datePublished": "2024-07-12T12:20:39.607Z", "dateUpdated": "2026-08-05T11:33:51.352Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:33:51.352Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/io-wq: Use set_bit() and test_bit() at worker->flags\n\nUtilize set_bit() and test_bit() on worker->flags within io_uring/io-wq\nto address potential data races.\n\nThe structure io_worker->flags may be accessed through various data\npaths, leading to concurrency issues. When KCSAN is enabled, it reveals\ndata races occurring in io_worker_handle_work and\nio_wq_activate_free_worker functions.\n\n\t BUG: KCSAN: data-race in io_worker_handle_work / io_wq_activate_free_worker\n\t write to 0xffff8885c4246404 of 4 bytes by task 49071 on cpu 28:\n\t io_worker_handle_work (io_uring/io-wq.c:434 io_uring/io-wq.c:569)\n\t io_wq_worker (io_uring/io-wq.c:?)\n\n\n\t read to 0xffff8885c4246404 of 4 bytes by task 49024 on cpu 5:\n\t io_wq_activate_free_worker (io_uring/io-wq.c:? io_uring/io-wq.c:285)\n\t io_wq_enqueue (io_uring/io-wq.c:947)\n\t io_queue_iowq (io_uring/io_uring.c:524)\n\t io_req_task_submit (io_uring/io_uring.c:1511)\n\t io_handle_tw_list (io_uring/io_uring.c:1198)\n\n\nLine numbers against commit 18daea77cca6 (\"Merge tag 'for-linus' of\ngit://git.kernel.org/pub/scm/virt/kvm/kvm\").\n\nThese races involve writes and reads to the same memory location by\ndifferent tasks running on different CPUs. To mitigate this, refactor\nthe code to use atomic operations such as set_bit(), test_bit(), and\nclear_bit() instead of basic \"and\" and \"or\" operations. This ensures\nthread-safe manipulation of worker flags.\n\nAlso, move `create_index` to avoid holes in the structure." } ], "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 - The race is reached only through local io_uring syscalls (`io_uring_setup(2)`/`io_uring_enter(2)`) on a ring the attacker owns, via `io_queue_iowq()` → `io_wq_enqueue()` → `io_wq_activate_free_worker()`. No network or adjacent-network data path touches `io_uring/io-wq.c`.\nAC:L - The attacker controls both sides of the race: it creates the io-wq workers, forces async punting with `IOSQE_ASYNC`, and submits from multiple threads so that `io_wq_activate_free_worker()` walks `wq->free_list` on one CPU while a worker executes the non-atomic `worker->flags &= ~IO_WORKER_F_FREE` in `__io_worker_busy()` on another. The window can be hit repeatedly at no cost, exactly as KCSAN observed under ordinary load.\nPR:L - Only an unprivileged local account is required — `io_uring_setup()` performs no capability check and `sysctl_io_uring_disabled` defaults to 0, permitting io_uring for all users; io-wq worker threads are created on demand for that user's own ring.\nUI:N - The attacking task performs every step itself — creating the ring, spawning submitter threads, and queueing async work — with no action required from any other user or administrator.\nS:U - The raced state and all its consequences live in the kernel's own io-wq bookkeeping for the calling task's ring; no VM, hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - The raced field is the sole guard on `wq->free_list` membership — `io_worker_exit()` unlinks `worker->nulls_node` only `if (worker->flags & IO_WORKER_F_FREE)` before `kfree_rcu(worker, rcu)` — so an indeterminate value leaves a freed `io_worker` linked and read by `io_wq_activate_free_worker()` from other tasks, which after slab reuse discloses attacker-observable kernel heap contents through `worker->wq` and `worker->task`.\nI:H - The same stale-flag path lets other tasks operate on a freed `io_worker`: `io_worker_get()` performs `refcount_inc_not_zero` into a reallocated slab object and `wake_up_process(worker->task)` dereferences a sprayable pointer into the scheduler, yielding a write and control-flow primitive.\nA:H - A wrong `IO_WORKER_F_BOUND` read makes `io_wq_activate_free_worker()` wake a worker from the other accounting class and return true, so `io_wq_enqueue()` skips `io_wq_create_worker()` and the queued work is left with no worker to run it — an indefinite hang of the io_uring request plus `acct->nr_running` imbalance, triggerable at will by an unprivileged user." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "io_uring/io-wq.c" ], "versions": [ { "version": "2b188cc1bb857a9d4701ae59aa7768b5124e262e", "lessThan": "ab702c3483db9046bab9f40306f1a28b22dbbdc0", "status": "affected", "versionType": "git" }, { "version": "2b188cc1bb857a9d4701ae59aa7768b5124e262e", "lessThan": "1cbb0affb15470a9621267fe0a8568007553a4bf", "status": "affected", "versionType": "git" }, { "version": "2b188cc1bb857a9d4701ae59aa7768b5124e262e", "lessThan": "8a565304927fbd28c9f028c492b5c1714002cbab", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "io_uring/io-wq.c" ], "versions": [ { "version": "5.1", "status": "affected" }, { "version": "0", "lessThan": "5.1", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.35", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.9.6", "lessThanOrEqual": "6.9.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.10", "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": "5.1", "versionEndExcluding": "6.6.35" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.1", "versionEndExcluding": "6.9.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.1", "versionEndExcluding": "6.10" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/ab702c3483db9046bab9f40306f1a28b22dbbdc0" }, { "url": "https://git.kernel.org/stable/c/1cbb0affb15470a9621267fe0a8568007553a4bf" }, { "url": "https://git.kernel.org/stable/c/8a565304927fbd28c9f028c492b5c1714002cbab" } ], "title": "io_uring/io-wq: Use set_bit() and test_bit() at worker->flags", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-02T04:26:15.901Z" }, "title": "CVE Program Container", "references": [ { "url": "https://git.kernel.org/stable/c/ab702c3483db9046bab9f40306f1a28b22dbbdc0", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/1cbb0affb15470a9621267fe0a8568007553a4bf", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/8a565304927fbd28c9f028c492b5c1714002cbab", "tags": [ "x_transferred" ] } ] }, { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2024-39508", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "version": "2.0.3", "timestamp": "2024-09-10T17:06:48.077960Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2024-09-11T17:32:47.742Z" } } ] } }