CVE-2026-80673ntfs: bound the look-ahead attribute-list entry in ntfs_external_attr_find()

Official description

In the Linux kernel, the following vulnerability has been resolved: ntfs: bound the look-ahead attribute-list entry in ntfs_external_attr_find() When resolving an attribute lookup with a non-zero @lowest_vcn, ntfs_external_attr_find() peeks at the next $ATTRIBUTE_LIST entry to decide whether to keep searching, but bounds that not-yet-validated entry only with "(u8 *)next_al_entry + 6 < al_end" (which proves just bytes 0..6 are in range) and "(u8 *)next_al_entry + length <= al_end" with an attacker-controlled, non-8-aligned length. It then reads next_al_entry->lowest_vcn (an __le64 at offset 8) and the name at next_al_entry->name_offset, both of which can lie past al_end -- the exact end of the kvmalloc'd attribute-list buffer (allocated at the on-disk attr_list_size, no rounding). A crafted on-disk $ATTRIBUTE_LIST whose last entry sits a few bytes before al_end therefore yields a slab out-of-bounds read when the inode is read. Validate the look-ahead entry with ntfs_attr_list_entry_is_valid() (added in patch 1/3) before dereferencing lowest_vcn and the name, so the same fixed-header, length and name bounds the main attribute-list walk uses now guard this read too.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/44885c9b45eb4082fb7f558590d84bb254a08e94
• https://git.kernel.org/stable/c/344b18f389f9934d59c7b0cf3d20541ea2e0da58