CVE-2024-57951 hrtimers: Handle CPU state correctly on hotplug
A use-after-free vulnerability in the Linux kernel's hrtimer subsystem during CPU hotplug operations can lead to system crashes or potential code execution.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-57951?
CVE-2024-57951 is a high-severity use after free vulnerability in Linux kernel, published on 12 Feb 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
hrtimers: Handle CPU state correctly on hotplug
Consider a scenario where a CPU transitions from CPUHP_ONLINE to halfway through a CPU hotunplug down to CPUHP_HRTIMERS_PREPARE, and then back to CPUHP_ONLINE:
Since hrtimers_prepare_cpu() does not run, cpu_base.hres_active remains set to 1 throughout. However, during a CPU unplug operation, the tick and the clockevents are shut down at CPUHP_AP_TICK_DYING. On return to the online state, for instance CFS incorrectly assumes that the hrtick is already active, and the chance of the clockevent device to transition to oneshot mode is also lost forever for the CPU, unless it goes back to a lower state than CPUHP_HRTIMERS_PREPARE once.
This round-trip reveals another issue; cpu_base.online is not set to 1 after the transition, which appears as a WARN_ON_ONCE in enqueue_hrtimer().
Aside of that, the bulk of the per CPU state is not reset either, which means there are dangling pointers in the worst case.
Address this by adding a corresponding startup() callback, which resets the stale per CPU state and sets the online flag.
[ tglx: Make the new callback unconditionally available, remove the online modification in the prepare() callback and clear the remaining state in the starting callback instead of the prepare callback ]
Weakness: CWE-416
Which versions are affected by CVE-2024-57951?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-57951?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2024-57951 being exploited?
There is no known exploitation of CVE-2024-57951 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-56803, AZL-56842, BELL-CVE-2024-57951, DEBIAN-CVE-2024-57951, GHSA-5j5f-9wh9-hfj9, UBUNTU-CVE-2024-57951.