CVE-2025-39939
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-10-04

Last updated on: 2026-03-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: iommu/s390: Fix memory corruption when using identity domain zpci_get_iommu_ctrs() returns counter information to be reported as part of device statistics; these counters are stored as part of the s390_domain. The problem, however, is that the identity domain is not backed by an s390_domain and so the conversion via to_s390_domain() yields a bad address that is zero'd initially and read on-demand later via a sysfs read. These counters aren't necessary for the identity domain; just return NULL in this case. This issue was discovered via KASAN with reports that look like: BUG: KASAN: global-out-of-bounds in zpci_fmb_enable_device when using the identity domain for a device on s390.
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Meta Information
Published
2025-10-04
Last Modified
2026-03-25
Generated
2026-06-16
AI Q&A
2025-10-04
EPSS Evaluated
2026-06-14
NVD
CVE-2025-39939
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
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Executive Summary

This vulnerability in the Linux kernel involves memory corruption when using the identity domain in the iommu/s390 subsystem. Specifically, a function called zpci_get_iommu_ctrs() returns device counter information stored in an s390_domain structure. However, the identity domain is not backed by an s390_domain, so converting it via to_s390_domain() results in an invalid address. This leads to reading from a zeroed address on-demand, causing memory corruption detected by KASAN.

Impact Analysis

The vulnerability can cause memory corruption in the Linux kernel when using the identity domain on s390 devices. This could lead to system instability, crashes, or unexpected behavior when device statistics are accessed, potentially affecting the reliability and security of systems using this configuration.

Detection Guidance

This vulnerability can be detected by monitoring kernel logs for KASAN (Kernel Address Sanitizer) reports indicating global-out-of-bounds errors related to zpci_fmb_enable_device when using the identity domain on s390 architecture. You can check for such errors using the command: dmesg | grep -i kasan

Mitigation Strategies

To mitigate this vulnerability, update your Linux kernel to a version where the fix for the identity domain memory corruption in iommu/s390 has been applied. Avoid using the identity domain for devices on s390 until the patch is applied.

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