Linux Kernel Hrtimer Vulnerability in CPU Hotplug Process
CVE-2025-21816
What is CVE-2025-21816?
A vulnerability exists in the Linux kernel related to the handling of high-resolution timers (hrtimers) during CPU hotplug events. When a CPU is being unplugged, if hrtimers are queued, they can sometimes still be triggered by the departing CPU, potentially resulting in timers being set for an offline CPU. This issue can lead to unexpected behavior, especially in real-time scheduling contexts, where the system might not respond as intended. To mitigate the risks associated with this vulnerability, improvements should be made in the hrtimer infrastructure, ensuring that timers are always migrated away from an offline CPU to an active one. This adjustment could eliminate the need for complex workarounds that have been proposed in the past.
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Affected Version(s)
Linux 75b5016ce325f1ef9c63e5398a1064cf8a7a7354 < 82ac6adbbb2aad14548a71d5e2e37f4964a15e38
Linux 53f408cad05bb987af860af22f4151e5a18e6ee8 < 63815bef47ec25f5a125019ca480882481ee1553
Linux 5c0930ccaad5a74d74e8b18b648c5eb21ed2fe94