CVE-2026-72377

Summary

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

afs: Remove setting of AS_RELEASE_ALWAYS for symlinks and mountpoints

Regular AFS files correctly use afs_file_aops which have release_folio set as netfs_release_folio, so AS_RELEASE_ALWAYS is valid for them when fscache is enabled (set via afs_vnode_set_cache()). Symlinks and mountpoints in AFS use afs_dir_aops, which does not provide a release_folio callback. However, afs_apply_status() unconditionally calls mapping_set_release_always() for these.

In such case when memory management code attempts to release folios, filemap_release_folio() checks folio_needs_release() which returns true due to AS_RELEASE_ALWAYS being set. Since there is no release_folio callback, it falls through to try_to_free_buffers(), which at present expects buffer_heads to be not null. For symlinks and mountpoints without buffer_heads, this causes pointer dereference.

[dh: Added more bits that were missed]

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/9d6b0f6d437e2f8350e08678e5e1d20c11c364f3
• https://git.kernel.org/stable/c/81e985b4c3a6cbcc443fcdcd3ebda7fcc845d459

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