ntfs: zero out stale data in straddle block beyond initialized_size

ntfs: zero out stale data in straddle block beyond initialized_size

ntfs_read_iomap_begin_non_resident() rounds up MAPPED extents
to the block boundary of initialized_size. This ensures that
any subsequent blocks are treated as IOMAP_UNWRITTEN, but
it also causes the "straddle block" containing initialized_size
to be read from disk. The disk data beyond initialized_size in
this block is stale and must be zeroed to prevent data leakage.

Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>