{"cve":"CVE-2023-53531","nvd":{"published":"2025-10-01T12:15:57.843","modified":"2026-08-04T10:19:10.767","status":"Modified","description":"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's 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(&nq->poll_lock)\n  list_splice_init(&nq->poll_list, &list)\n  spin_unlock(&nq->poll_lock)\n\n  while (!list_empty(&list))\n    req = list_first_entry()\n    list_del_init()\n    ...\n    blk_mq_add_to_batch()\n    // req->rq_next = NULL\n\t\t\t\t\tspin_lock(&nq->poll_lock)\n\n\t\t\t\t\t// rq->queuelist->next == NULL\n\t\t\t\t\tlist_del_init(&rq->queuelist)\n\n\t\t\t\t\tspin_unlock(&nq->poll_lock)\n\nFix these problems by setting requests state to MQ_RQ_COMPLETE under\nnq->poll_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/","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-476"],"references":["https://git.kernel.org/stable/c/5a26e45edb4690d58406178b5a9ea4c6dcf2c105","https://git.kernel.org/stable/c/a0b4a0666beacfe8add9c71d8922475541dbae73","https://git.kernel.org/stable/c/a7cb2e709f2927cc3c76781df3e45de2381b3b9d"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:11:26.888974865+00:00"},"epss":{"cve":"CVE-2023-53531","score":0.00154,"percentile":0.04535,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}