Bug 2406767 (CVE-2025-40067)

Summary: CVE-2025-40067 kernel: fs/ntfs3: reject index allocation if $BITMAP is empty but blocks exist
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Description OSIDB Bzimport 2025-10-28 12:04:27 UTC 
In the Linux kernel, the following vulnerability has been resolved:

fs/ntfs3: reject index allocation if $BITMAP is empty but blocks exist

Index allocation requires at least one bit in the $BITMAP attribute to
track usage of index entries. If the bitmap is empty while index blocks
are already present, this reflects on-disk corruption.

syzbot triggered this condition using a malformed NTFS image. During a
rename() operation involving a long filename (which spans multiple
index entries), the empty bitmap allowed the name to be added without
valid tracking. Subsequent deletion of the original entry failed with
-ENOENT, due to unexpected index state.

Reject such cases by verifying that the bitmap is not empty when index
blocks exist.
Comment 1 Jon Moroney 2025-10-28 18:05:57 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025102817-CVE-2025-40067-fb1b@gregkh/T