Bug 2492405 (CVE-2026-53043)

Summary: CVE-2026-53043 kernel: ocfs2/dlm: validate qr_numregions in dlm_match_regions()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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OS: Linux   
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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.
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Description OSIDB Bzimport 2026-06-24 18:10:34 UTC 
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.


This patch (of 2):

The qr_numregions field from a DLM_QUERY_REGION network message is used
directly as loop bounds in dlm_match_regions() without checking against
O2NM_MAX_REGIONS.  Since qr_regions is sized for at most O2NM_MAX_REGIONS
(32) entries, a crafted message with qr_numregions > 32 causes
out-of-bounds reads past the qr_regions buffer.

Add a bounds check for qr_numregions before entering the loops.
Comment 1 Keith Grant 2026-06-25 20:19:24 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062457-CVE-2026-53043-5980@gregkh/T