Advisory [CVE-2026-53043] validate qr_numregions in dlm_match_regions

In the Linux kernel, the following vulnerability has been resolved: ocfs2/dlm: validate qr_numregions in dlm_match_regions() Patch series "ocfs2/dlm: fix two bugs in dlm_match_regions()". In dlm_match_regions(), the qr_numregions field from a DLM_QUERY_REGION network message is used to drive loops over the qr_regions buffer without sufficient validation.

This series fixes two issues: - Patch 1 adds a bounds check to reject messages where qr_numregions exceeds O2NM_MAX_REGIONS.

The o2net layer only validates message byte length; it does not constrain field values, so a crafted message can set qr_numregions up to 255 and trigger out-of-bounds reads past the 1024-byte qr_regions buffer. - Patch 2 fixes an off-by-one in the local-vs-remote comparison loop, which uses '<=' instead of '<', reading one entry past the valid range even when qr_numregions is within bounds.

Add a bounds check for qr_numregions before entering the loops. A flaw was found in the Linux kernel's Oracle Cluster File System 2 (OCFS2) Distributed Lock Manager (DLM).

A remote attacker could exploit this vulnerability by sending a specially crafted network message. Insufficient validation of the qr_numregions field in the dlm_match_regions() function allows for out-of-bounds reads past a buffer, which could lead to information disclosure or a denial of service.

Red Hat severity: not rated. Weakness: CWE-1285.