{"id":"CVE-2025-21767","url":"https://www.cyber-defence.io/tools/cve/CVE-2025-21767","generatedAt":"2026-10-28T01:13:57.149Z","title":"In the Linux kernel, the following vulnerability has been resolved: clocksource: Use migrate_disable() to avoid calling get_random_u32() in atomic context The following bug report happened with a PREEMPT_RT kernel: BUG: sleeping function called from…","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nclocksource: Use migrate_disable() to avoid calling get_random_u32() in atomic context\n\nThe following bug report happened with a PREEMPT_RT kernel:\n\n  BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48\n  in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2012, name: kwatchdog\n  preempt_count: 1, expected: 0\n  RCU nest depth: 0, expected: 0\n  get_random_u32+0x4f/0x110\n  clocksource_verify_choose_cpus+0xab/0x1a0\n  clocksource_verify_percpu.part.0+0x6b/0x330\n  clocksource_watchdog_kthread+0x193/0x1a0\n\nIt is due to the fact that clocksource_verify_choose_cpus() is invoked with\npreemption disabled.  This function invokes get_random_u32() to obtain\nrandom numbers for choosing CPUs.  The batched_entropy_32 local lock and/or\nthe base_crng.lock spinlock in driver/char/random.c will be acquired during\nthe call. In PREEMPT_RT kernel, they are both sleeping locks and so cannot\nbe acquired in atomic context.\n\nFix this problem by using migrate_disable() to allow smp_processor_id() to\nbe reliably used without introducing atomic context. preempt_disable() is\nthen called after clocksource_verify_choose_cpus() but before the\nclocksource measurement is being run to avoid introducing unexpected\nlatency.","published":"2025-02-27T03:15:17.000Z","lastModified":"2026-10-15T02:17:35.000Z","status":"Modified","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":5.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-667"],"affected":["linux/linux kernel"],"epss":{"score":0.00178,"percentile":0.07337,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.18%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/0fb534187d2355f6c8f995321e76d1ccd1262ac1","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/60f54f0d4ea530950549a8263e6fdd70a40490a4","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/6bb05a33337b2c842373857b63de5c9bf1ae2a09","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/852805b6cbdb69c298a8fc9fbe79994c95106e04","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/8783ceeee797d9aa9cfe150690fb9d0bac8cc459","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/cc3d79e7c806cb57d71c28a4a35e7d7fb3265faa","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d9c217fadfcff7a8df58567517d1e4253f3fd243","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-082556.html","source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-784472.html","source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2025-21767","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}