GHSA-H97W-34CR-4PXX
Vulnerability from github – Published: 2025-02-27 03:34 – Updated: 2026-05-12 15:30In 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.
{
"affected": [],
"aliases": [
"CVE-2025-21767"
],
"database_specific": {
"cwe_ids": [
"CWE-667"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-02-27T03:15:17Z",
"severity": "MODERATE"
},
"details": "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.",
"id": "GHSA-h97w-34cr-4pxx",
"modified": "2026-05-12T15:30:48Z",
"published": "2025-02-27T03:34:05Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21767"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0fb534187d2355f6c8f995321e76d1ccd1262ac1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/60f54f0d4ea530950549a8263e6fdd70a40490a4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6bb05a33337b2c842373857b63de5c9bf1ae2a09"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/852805b6cbdb69c298a8fc9fbe79994c95106e04"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8783ceeee797d9aa9cfe150690fb9d0bac8cc459"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cc3d79e7c806cb57d71c28a4a35e7d7fb3265faa"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d9c217fadfcff7a8df58567517d1e4253f3fd243"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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