CVE-2026-53043 — ocfs2/dlm: validate qr_numregions in dlm_match_regions()

Affected: Linux

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.

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CVE-2026-53043 — ocfs2/dlm: validate qr_numregions in dlm_match_regions()