ntfs: validate resident attribute lists and harden the validator

ntfs: validate resident attribute lists and harden the validator

A base inode's $ATTRIBUTE_LIST is sanity-checked by load_attribute_list()
only on the non-resident path; ntfs_read_locked_inode() copies a *resident*
attribute list into ni->attr_list with a plain memcpy() and no validation
at all. Every subsequent walk of ni->attr_list --
ntfs_external_attr_find(), ntfs_inode_attach_all_extents() and
ntfs_attrlist_need() -- then trusts the entries are well-formed and reads
attr_list_entry fixed-header fields
(lowest_vcn at offset 8, mft_reference at offset 16, and the name) with
bounds that assume validation already happened. A crafted resident
attribute list therefore reaches those walks unvalidated and can drive
out-of-bounds reads of the attribute-list buffer.

load_attribute_list() itself reads ale->name_offset (offset 7),
ale->mft_reference (offset 16) and the name length under only an
"al < al_start + size" bound, so its own validation loop can over-read the
fixed header of a truncated trailing entry by a few bytes.

Factor the per-entry validation into ntfs_attr_list_entry_is_valid(),
which requires each entry's fixed header (offsetof(struct
attr_list_entry, name)) to be in range before any field is dereferenced,
that ale->length is a multiple of 8 covering the fixed header plus the
name, and that the entry is in use and carries a live MFT reference.
ntfs_attr_list_is_valid() walks the buffer with it and checks the entries
tile it exactly. Use the list validator in load_attribute_list()
(replacing the open-coded loop, closing its own over-read) and on the
resident path in ntfs_read_locked_inode() (which previously skipped
validation entirely); patches 2/3 reuse the per-entry helper at the other
two attribute-list walks.

Fixes: 1e9ea7e04472 ("Revert "fs: Remove NTFS classic"")
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>