Bug 2516545 (CVE-2026-72159)

In the Linux kernel, the following vulnerability has been resolved:

ocfs2: reject non-inline dinodes with i_size and zero i_clusters

On a volume mounted without OCFS2_FEATURE_INCOMPAT_SPARSE_ALLOC, a
non-inline regular file with non-zero i_size and zero i_clusters is
structurally malformed: the extent map declares no allocated clusters yet
the size header claims content exists.  Keep rejecting that shape, but
express it through a shared predicate so the same invariant is available
to normal inode reads and online filecheck.

The same zero-cluster shape is also malformed for non-inline directories. 
ocfs2 directory growth allocates backing storage before advancing i_size,
and ocfs2_dir_foreach_blk_el() later walks until ctx->pos reaches
i_size_read(inode).  A forged directory dinode with a huge i_size and no
clusters would repeatedly fail on holes while advancing through the
claimed size.

Sparse regular files remain exempt: on sparse-alloc volumes, truncate can
legitimately grow i_size without allocating clusters.  System inodes and
inline-data dinodes also retain their separate storage rules.

Mirror the check in ocfs2_filecheck_validate_inode_block() as well. 
filecheck reports through its own error namespace, so malformed
size/cluster state is logged as a filecheck invalid-inode result rather
than via ocfs2_error(), but it must not proceed into
ocfs2_populate_inode().