{"id":"CVE-2025-21767","summary":"clocksource: Use migrate_disable() to avoid calling get_random_u32() in atomic context","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.","modified":"2026-03-20T12:41:09.696325Z","published":"2025-02-27T02:18:17.067Z","related":["SUSE-SU-2025:01919-1","SUSE-SU-2025:0847-1","SUSE-SU-2025:0856-1","SUSE-SU-2025:0955-1","SUSE-SU-2025:20190-1","SUSE-SU-2025:20192-1","SUSE-SU-2025:20260-1","SUSE-SU-2025:20270-1","USN-7521-2"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21767.json","cna_assigner":"Linux"},"references":[{"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"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21767.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21767"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"d9b40ebd448e437ffbc65f013836f98252279a82"},{"fixed":"d9c217fadfcff7a8df58567517d1e4253f3fd243"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"7560c02bdffb7c52d1457fa551b9e745d4b9e754"},{"fixed":"60f54f0d4ea530950549a8263e6fdd70a40490a4"},{"fixed":"852805b6cbdb69c298a8fc9fbe79994c95106e04"},{"fixed":"8783ceeee797d9aa9cfe150690fb9d0bac8cc459"},{"fixed":"cc3d79e7c806cb57d71c28a4a35e7d7fb3265faa"},{"fixed":"0fb534187d2355f6c8f995321e76d1ccd1262ac1"},{"fixed":"6bb05a33337b2c842373857b63de5c9bf1ae2a09"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0"},{"last_affected":"193e14e68e907b2a7a936a7726accbaa4df25a4d"},{"last_affected":"155d3c5d24ee13cafa6236b49fc02b240a511d59"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-21767.json"}}],"schema_version":"1.7.5"}