CVE-2025-38055 perf/x86/intel: Fix segfault with PEBS-via-PT with sample_freq
A local attacker can trigger a kernel segfault and denial of service by using PEBS-via-PT with sample frequency in the Linux kernel.
- 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-2025-38055?
CVE-2025-38055 is a medium-severity vulnerability in Linux kernel, published on 18 Jun 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:
perf/x86/intel: Fix segfault with PEBS-via-PT with sample_freq
Currently, using PEBS-via-PT with a sample frequency instead of a sample period, causes a segfault. For example:
BUG: kernel NULL pointer dereference, address: 0000000000000195 <NMI> ? __die_body.cold+0x19/0x27 ? page_fault_oops+0xca/0x290 ? exc_page_fault+0x7e/0x1b0 ? asm_exc_page_fault+0x26/0x30 ? intel_pmu_pebs_event_update_no_drain+0x40/0x60 ? intel_pmu_pebs_event_update_no_drain+0x32/0x60 intel_pmu_drain_pebs_icl+0x333/0x350 handle_pmi_common+0x272/0x3c0 intel_pmu_handle_irq+0x10a/0x2e0 perf_event_nmi_handler+0x2a/0x50
That happens because intel_pmu_pebs_event_update_no_drain() assumes all the pebs_enabled bits represent counter indexes, which is not always the case. In this particular case, bits 60 and 61 are set for PEBS-via-PT purposes.
The behaviour of PEBS-via-PT with sample frequency is questionable because although a PMI is generated (PEBS_PMI_AFTER_EACH_RECORD), the period is not adjusted anyway.
Putting that aside, fix intel_pmu_pebs_event_update_no_drain() by passing the mask of counter bits instead of 'size'. Note, prior to the Fixes commit, 'size' would be limited to the maximum counter index, so the issue was not hit.
Weakness: CWE-476
Which versions are affected by CVE-2025-38055?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-38055?
Apply the vendor's patch.
Is CVE-2025-38055 being exploited?
There is no known exploitation of CVE-2025-38055 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-38055, DEBIAN-CVE-2025-38055, GHSA-hwwv-phfq-243p, ROOT-OS-UBUNTU-2404-CVE-2025-38055, UBUNTU-CVE-2025-38055.