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CVE-2023-53531 (GCVE-0-2023-53531)

Vulnerability from cvelistv5 – Published: 2025-10-01 11:46 – Updated: 2026-08-05 09:14
VLAI
Title
null_blk: fix poll request timeout handling
Summary
In the Linux kernel, the following vulnerability has been resolved: null_blk: fix poll request timeout handling When doing io_uring benchmark on /dev/nullb0, it's easy to crash the kernel if poll requests timeout triggered, as reported by David. [1] BUG: kernel NULL pointer dereference, address: 0000000000000008 Workqueue: kblockd blk_mq_timeout_work RIP: 0010:null_timeout_rq+0x4e/0x91 Call Trace: ? null_timeout_rq+0x4e/0x91 blk_mq_handle_expired+0x31/0x4b bt_iter+0x68/0x84 ? bt_tags_iter+0x81/0x81 __sbitmap_for_each_set.constprop.0+0xb0/0xf2 ? __blk_mq_complete_request_remote+0xf/0xf bt_for_each+0x46/0x64 ? __blk_mq_complete_request_remote+0xf/0xf ? percpu_ref_get_many+0xc/0x2a blk_mq_queue_tag_busy_iter+0x14d/0x18e blk_mq_timeout_work+0x95/0x127 process_one_work+0x185/0x263 worker_thread+0x1b5/0x227 This is indeed a race problem between null_timeout_rq() and null_poll(). null_poll() null_timeout_rq() spin_lock(&nq->poll_lock) list_splice_init(&nq->poll_list, &list) spin_unlock(&nq->poll_lock) while (!list_empty(&list)) req = list_first_entry() list_del_init() ... blk_mq_add_to_batch() // req->rq_next = NULL spin_lock(&nq->poll_lock) // rq->queuelist->next == NULL list_del_init(&rq->queuelist) spin_unlock(&nq->poll_lock) Fix these problems by setting requests state to MQ_RQ_COMPLETE under nq->poll_lock protection, in which null_timeout_rq() can safely detect this race and early return. Note this patch just fix the kernel panic when request timeout happen. [1] https://lore.kernel.org/all/3893581.1691785261@warthog.procyon.org.uk/
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 0a593fbbc245a85940ed34caa3aa1e4cb060c54b , < a0b4a0666beacfe8add9c71d8922475541dbae73 (git)
Affected: 0a593fbbc245a85940ed34caa3aa1e4cb060c54b , < a7cb2e709f2927cc3c76781df3e45de2381b3b9d (git)
Affected: 0a593fbbc245a85940ed34caa3aa1e4cb060c54b , < 5a26e45edb4690d58406178b5a9ea4c6dcf2c105 (git)
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Linux Linux Affected: 5.16
Unaffected: 0 , < 5.16 (semver)
Unaffected: 6.1.54 , ≤ 6.1.* (semver)
Unaffected: 6.5.4 , ≤ 6.5.* (semver)
Unaffected: 6.6 , ≤ * (original_commit_for_fix)
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          "product": "Linux",
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnull_blk: fix poll request timeout handling\n\nWhen doing io_uring benchmark on /dev/nullb0, it\u0027s easy to crash the\nkernel if poll requests timeout triggered, as reported by David. [1]\n\nBUG: kernel NULL pointer dereference, address: 0000000000000008\nWorkqueue: kblockd blk_mq_timeout_work\nRIP: 0010:null_timeout_rq+0x4e/0x91\nCall Trace:\n ? null_timeout_rq+0x4e/0x91\n blk_mq_handle_expired+0x31/0x4b\n bt_iter+0x68/0x84\n ? bt_tags_iter+0x81/0x81\n __sbitmap_for_each_set.constprop.0+0xb0/0xf2\n ? __blk_mq_complete_request_remote+0xf/0xf\n bt_for_each+0x46/0x64\n ? __blk_mq_complete_request_remote+0xf/0xf\n ? percpu_ref_get_many+0xc/0x2a\n blk_mq_queue_tag_busy_iter+0x14d/0x18e\n blk_mq_timeout_work+0x95/0x127\n process_one_work+0x185/0x263\n worker_thread+0x1b5/0x227\n\nThis is indeed a race problem between null_timeout_rq() and null_poll().\n\nnull_poll()\t\t\t\tnull_timeout_rq()\n  spin_lock(\u0026nq-\u003epoll_lock)\n  list_splice_init(\u0026nq-\u003epoll_list, \u0026list)\n  spin_unlock(\u0026nq-\u003epoll_lock)\n\n  while (!list_empty(\u0026list))\n    req = list_first_entry()\n    list_del_init()\n    ...\n    blk_mq_add_to_batch()\n    // req-\u003erq_next = NULL\n\t\t\t\t\tspin_lock(\u0026nq-\u003epoll_lock)\n\n\t\t\t\t\t// rq-\u003equeuelist-\u003enext == NULL\n\t\t\t\t\tlist_del_init(\u0026rq-\u003equeuelist)\n\n\t\t\t\t\tspin_unlock(\u0026nq-\u003epoll_lock)\n\nFix these problems by setting requests state to MQ_RQ_COMPLETE under\nnq-\u003epoll_lock protection, in which null_timeout_rq() can safely detect\nthis race and early return.\n\nNote this patch just fix the kernel panic when request timeout happen.\n\n[1] https://lore.kernel.org/all/3893581.1691785261@warthog.procyon.org.uk/"
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              "value": "AV:L - Exploitation requires opening the local block device /dev/nullb0 and issuing polled direct I/O (io_uring IOPOLL or preadv2 RWF_HIPRI); there is no remote or adjacent-network path into null_blk.\nAC:L - The attacker controls both sides of the race \u2014 it submits the polled requests, controls when it calls into null_poll(), and the 5-second timeout is fixed unconditionally by null_add_dev() (tag_set-\u003etimeout = 5 * HZ), so the collision with blk_mq_timeout_work can be arranged deterministically and retried; the fix author notes it is \"easy to crash the kernel.\"\nPR:L - The vulnerable path contains no capability or namespace check \u2014 any local user able to open the null_blk device node (group disk, benchmarking/CI accounts, or a container handed the device) can reach null_queue_rq/null_poll with ordinary O_DIRECT reads.\nUI:N - The attacker performs the submissions and polling itself; no victim action is required to trigger the race.\nS:U - The corruption is confined to kernel block-layer structures within the same security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Beyond the NULL case, list_del_init() writes \u0026rq-\u003equeuelist into the io_comp_batch chain, so blk_mq_end_request_batch() dereferences a bogus struct request and bio pointers, and the double blk_mq_complete_request() frees the tag twice yielding request reuse \u2014 a UAF-class read primitive over kernel heap contents.\nI:H - The race produces doubly-linked-list corruption plus double request completion (tag double-free and reallocation to a concurrent I/O), giving attacker-influenced kernel heap writes exploitable for control-flow hijacking.\nA:H - The documented result is a kernel NULL pointer dereference oops at address 0x8 inside blk_mq_timeout_work on the kblockd workqueue, killing the worker and panicking or wedging the block layer."
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-04T19:18:13+00:00",
      "cve": "CVE-2023-53531",
      "id": "CVE-2023-53531",
      "initial_release_date": "2023-01-01T00:00:00+00:00",
      "product_status:fixed": "280",
      "product_status:known_affected": "22",
      "product_status:known_not_affected": "174",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: null_blk: fix poll request timeout handling",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2023/cve-2023-53531.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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