CVE-2025-38055: perf/x86/intel: Fix segfault with PEBS-via-PT with sample_freq
In the Linux kernel, the following vulnerability has been resolved:
perf/x86/intel: Fix segfault with PEBS-via-PT with samplefreq
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> ? diebody.cold+0x19/0x27 ? pagefaultoops+0xca/0x290 ? excpagefault+0x7e/0x1b0 ? asmexcpagefault+0x26/0x30 ? intelpmupebseventupdatenodrain+0x40/0x60 ? intelpmupebseventupdatenodrain+0x32/0x60 intelpmudrainpebsicl+0x333/0x350 handlepmicommon+0x272/0x3c0 intelpmuhandleirq+0x10a/0x2e0 perfeventnmihandler+0x2a/0x50
That happens because intelpmupebseventupdatenodrain() assumes all the pebsenabled 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 (PEBSPMIAFTEREACHRECORD), the period is not adjusted anyway.
Putting that aside, fix intelpmupebseventupdatenodrain() 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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Event History
Frequently Asked Questions
What is the severity of CVE-2025-38055?
CVE-2025-38055 is considered a high severity vulnerability due to the potential for causing a kernel segfault.
How do I fix CVE-2025-38055?
To fix CVE-2025-38055, update your Linux kernel to the latest stable version that addresses this vulnerability.
What causes the segfault in CVE-2025-38055?
CVE-2025-38055 causes a segfault when using PEBS-via-PT with a sample frequency instead of a sample period.
Which versions of the Linux kernel are affected by CVE-2025-38055?
CVE-2025-38055 affects certain versions of the Linux kernel where PEBS-via-PT is implemented.
Is CVE-2025-38055 exploitable remotely?
CVE-2025-38055 is not directly exploitable remotely as it pertains to a kernel-level segfault during specific operations.