ksmbd: fix named stream write and EOF handling

An SMB WRITE to an existing named stream can silently discard data after
its written range. ksmbd stores streams as xattr values, but the write
path passes offset + count as the length of the replacement xattr even
when the old stream is longer. Writing 26 bytes at offset 0 to a 60-byte
stream reports 26 bytes written while discarding the remaining 34 bytes.

Keep the existing xattr length when an in-place write ends before EOF.
Reject writes that cross XATTR_SIZE_MAX rather than storing only the
portion that fits while reporting the full requested count.

Commit 4ea0bb8aaedf ("ksmbd: handle set/get info file for streamed file")
intentionally skipped ordinary inode truncation for stream handles: an
EOF SetInfo on an ADS had truncated the base file. That fixed the base
file corruption but left stream EOF changes reporting success without
resizing the stream. Handle these requests by resizing only the stream
xattr; the base file size remains untouched. Zero-fill stream extensions.
This is needed alongside the write fix: a short write's accidental
truncation previously masked an ignored explicit EOF change. The stream
resize helper returns xattr errors directly rather than using the
base-file truncate path's EBADF conversion.

Fixes: f44158485826 ("cifsd: add file operations")
Fixes: 4ea0bb8aaedf ("ksmbd: handle set/get info file for streamed file")
Cc: stable@vger.kernel.org
Signed-off-by: DaeMyung Kang <charsyam@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

0 files changed, 0 insertions, 0 deletions