CVE-2025-21767

Summary

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxd9b40ebd448e437ffbc65f013836f98252279a82 < d9c217fadfcff7a8df58567517d1e4253f3fd243affected
LinuxLinux7560c02bdffb7c52d1457fa551b9e745d4b9e754 < 60f54f0d4ea530950549a8263e6fdd70a40490a4affected
LinuxLinux7560c02bdffb7c52d1457fa551b9e745d4b9e754 < 852805b6cbdb69c298a8fc9fbe79994c95106e04affected
LinuxLinux7560c02bdffb7c52d1457fa551b9e745d4b9e754 < 8783ceeee797d9aa9cfe150690fb9d0bac8cc459affected
LinuxLinux7560c02bdffb7c52d1457fa551b9e745d4b9e754 < cc3d79e7c806cb57d71c28a4a35e7d7fb3265faaaffected
LinuxLinux7560c02bdffb7c52d1457fa551b9e745d4b9e754 < 0fb534187d2355f6c8f995321e76d1ccd1262ac1affected
LinuxLinux7560c02bdffb7c52d1457fa551b9e745d4b9e754 < 6bb05a33337b2c842373857b63de5c9bf1ae2a09affected
LinuxLinux193e14e68e907b2a7a936a7726accbaa4df25a4daffected
LinuxLinux155d3c5d24ee13cafa6236b49fc02b240a511d59affected
LinuxLinux5.10.50 < 5.10.235affected
LinuxLinux5.12.17 < 5.13affected
LinuxLinux5.13.2 < 5.14affected
LinuxLinux5.14affected
LinuxLinux0 < 5.14unaffected
LinuxLinux5.10.235 <= 5.10.*unaffected
LinuxLinux5.15.179 <= 5.15.*unaffected
LinuxLinux6.1.129 <= 6.1.*unaffected
LinuxLinux6.6.79 <= 6.6.*unaffected
LinuxLinux6.12.16 <= 6.12.*unaffected
LinuxLinux6.13.4 <= 6.13.*unaffected
LinuxLinux6.14 <= *unaffected

Weaknesses

ADP Enrichment

CVE Program Container

Additional References

Additional References

References