CVE-2025-21767clocksource: Use migrate_disable() to avoid calling get_random_u32() in atomic context
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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 invalid context at kernel/locking/spinlock_rt.c:48 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2012, name: kwatchdog preempt_count: 1, expected: 0 RCU nest depth: 0, expected: 0 get_random_u32+0x4f/0x110 clocksource_verify_choose_cpus+0xab/0x1a0 clocksource_verify_percpu.part.0+0x6b/0x330 clocksource_watchdog_kthread+0x193/0x1a0 It is due to the fact that clocksource_verify_choose_cpus() is invoked with preemption disabled. This function invokes get_random_u32() to obtain random numbers for choosing CPUs. The batched_entropy_32 local lock and/or the base_crng.lock spinlock in driver/char/random.c will be acquired during the call. In PREEMPT_RT kernel, they are both sleeping locks and so cannot be acquired in atomic context. Fix this problem by using migrate_disable() to allow smp_processor_id() to be reliably used without introducing atomic context. preempt_disable() is then called after clocksource_verify_choose_cpus() but before the clocksource measurement is being run to avoid introducing unexpected latency.
- CVSS
- 5.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Modified
- Record last updated
- Oct 15, 2026
- First seen by InfoSec Signals
- Oct 15, 2026
Affected products
Linux Linux linux:linux (from the name) | from d9b40ebd448e437ffbc65f013836f98252279a82 before d9c217fadfcff7a8df58567517d1e4253f3fd243; 7560c02bdffb7c52d1457fa551b9e745d4b9e754 builds before 60f54f0d4ea530950549a8263e6fdd70a40490a4; from 7560c02bdffb7c52d1457fa551b9e745d4b9e754 before 852805b6cbdb69c298a8fc9fbe79994c95106e04; from 7560c02bdffb7c52d1457fa551b9e745d4b9e754 before 8783ceeee797d9aa9cfe150690fb9d0bac8cc459; from 7560c02bdffb7c52d1457fa551b9e745d4b9e754 before cc3d79e7c806cb57d71c28a4a35e7d7fb3265faa; 7560c02bdffb7c52d1457fa551b9e745d4b9e754 builds before 0fb534187d2355f6c8f995321e76d1ccd1262ac1; 7560c02bdffb7c52d1457fa551b9e745d4b9e754 builds before 6bb05a33337b2c842373857b63de5c9bf1ae2a09; 193e14e68e907b2a7a936a7726accbaa4df25a4d; and 4 more ranges | CNA record |
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.5 | CISA ADP |
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name) | from V3.1.5 | CISA ADP |
Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem siemens:simatic_s7_1500_tm_mfp_gnu_linux_subsystem (from the name) | all versions | CISA ADP |
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.5 | CISA ADP |
linux linux_kernel linux:linux_kernel | from 5.10.50 before 5.10.235; from 5.12.17 before 5.13; from 5.13.2 before 5.15.179; from 5.16 before 6.1.129; from 6.2 before 6.6.79; from 6.7 before 6.12.16; from 6.13 before 6.13.4; 6.14 | NVD |
References
- https://git.kernel.org/stable/c/d9c217fadfcff7a8df58567517d1e4253f3fd243patch
- https://git.kernel.org/stable/c/60f54f0d4ea530950549a8263e6fdd70a40490a4patch
- https://git.kernel.org/stable/c/852805b6cbdb69c298a8fc9fbe79994c95106e04patch
- https://git.kernel.org/stable/c/8783ceeee797d9aa9cfe150690fb9d0bac8cc459patch
- https://git.kernel.org/stable/c/cc3d79e7c806cb57d71c28a4a35e7d7fb3265faapatch
- https://git.kernel.org/stable/c/0fb534187d2355f6c8f995321e76d1ccd1262ac1patch
- https://git.kernel.org/stable/c/6bb05a33337b2c842373857b63de5c9bf1ae2a09patch
- https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
- https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html
- https://cert-portal.siemens.com/productcert/html/ssa-784472.html
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.