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ntfs: move attribute payload before shrinking its record

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ntfs_new_attr_flags() resizes the non-resident attribute record before
moving its name and mapping pairs to their shorter-header offsets when
compression or sparse state is cleared.

Shrinking the record first moves the following attribute over the tail of
the old record. The subsequent memmove() therefore copies bytes from that
following attribute instead of the old mapping pairs. Re-enabling
compression on an empty file persists those bytes as a malformed mapping
pairs array, which ntfsck reports as a missing or invalid run length.

Move the payload before shrinking the record, while retaining the existing
resize-before-move ordering when growing it.

Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
This commit is contained in:
Namjae Jeon 2026-07-21 15:58:08 +09:00
parent 7ed0028126
commit 0ab6dc1ac4
1 changed files with 15 additions and 8 deletions
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23
fs/ntfs/ea.c
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@ -631,7 +631,7 @@ static int ntfs_new_attr_flags(struct ntfs_inode *ni, __le32 fattr)
struct attr_record *a;
__le16 new_aflags;
u16 old_name_ofs, old_mp_ofs;
int mp_size, mp_ofs, name_ofs, arec_size, err;
int mp_size, mp_ofs, name_ofs, old_arec_size, arec_size, err;
m = map_mft_record(ni);
if (IS_ERR(m))
@ -726,6 +726,19 @@ static int ntfs_new_attr_flags(struct ntfs_inode *ni, __le32 fattr)
mp_ofs = (name_ofs + a->name_length * sizeof(__le16) + 7) & ~7;
arec_size = (mp_ofs + mp_size + 7) & ~7;
old_arec_size = le32_to_cpu(a->length);
/*
* Move payloads before shrinking the record. Otherwise resizing moves
* the following attribute over the old payload before it can be copied.
*/
if (arec_size < old_arec_size) {
if (a->name_length && name_ofs != old_name_ofs)
memmove((u8 *)a + name_ofs, (u8 *)a + old_name_ofs,
a->name_length * sizeof(__le16));
if (mp_ofs != old_mp_ofs)
memmove((u8 *)a + mp_ofs, (u8 *)a + old_mp_ofs, mp_size);
}
err = ntfs_attr_record_resize(m, a, arec_size);
if (unlikely(err))
@ -736,18 +749,12 @@ static int ntfs_new_attr_flags(struct ntfs_inode *ni, __le32 fattr)
* shrinks by the compressed_size field. Update the in-record payload layout
* to match the new offsets before exposing the new mapping_pairs_offset.
*/
if (name_ofs > old_name_ofs) {
if (arec_size > old_arec_size) {
if (mp_ofs != old_mp_ofs)
memmove((u8 *)a + mp_ofs, (u8 *)a + old_mp_ofs, mp_size);
if (a->name_length)
memmove((u8 *)a + name_ofs, (u8 *)a + old_name_ofs,
a->name_length * sizeof(__le16));
} else {
if (a->name_length && name_ofs != old_name_ofs)
memmove((u8 *)a + name_ofs, (u8 *)a + old_name_ofs,
a->name_length * sizeof(__le16));
if (mp_ofs != old_mp_ofs)
memmove((u8 *)a + mp_ofs, (u8 *)a + old_mp_ofs, mp_size);
}
if (new_aflags & (ATTR_IS_SPARSE | ATTR_IS_COMPRESSED)) {