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CVE-2025-21767

clocksource: Use migrate_disable() to avoid calling get_random_u32() in atomic context

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.235, 5.13, 5.14, 5.15.179, 6.1.129, and 3 more
None on Exploit-DB, Metasploit or GitHub

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.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From d9b40ebd448e437ffbc65f013836f98252279a82 · fixed in d9c217fadfcff7a8df58567517d1e4253f3fd243; From 7560c02bdffb7c52d1457fa551b9e745d4b9e754 · fixed in 60f54f0d4ea530950549a8263e6fdd70a40490a4; From 7560c02bdffb7c52d1457fa551b9e745d4b9e754 · fixed in 852805b6cbdb69c298a8fc9fbe79994c95106e04; From 7560c02bdffb7c52d1457fa551b9e745d4b9e754 · fixed in 8783ceeee797d9aa9cfe150690fb9d0bac8cc459; From 7560c02bdffb7c52d1457fa551b9e745d4b9e754 · fixed in cc3d79e7c806cb57d71c28a4a35e7d7fb3265faa; From 7560c02bdffb7c52d1457fa551b9e745d4b9e754 · fixed in 0fb534187d2355f6c8f995321e76d1ccd1262ac1; From 7560c02bdffb7c52d1457fa551b9e745d4b9e754 · fixed in 6bb05a33337b2c842373857b63de5c9bf1ae2a09; From 5.10.50 · fixed in 5.10.235; From 5.12.17 · fixed in 5.13; From 5.13.2 · fixed in 5.14

  • Linux Linux

    5.14

  • KernelLinux

    fixed in 5.10.235; From 5.11.0 · fixed in 5.15.179; From 5.14.0 · fixed in 6.1.129; From 5.16.0 · fixed in 6.6.79; From 6.2.0 · fixed in 6.12.16; From 6.7.0 · fixed in 6.13.4

References 7

git.kernel.org