f2fs: reject overlapping move range after len expansion

F2FS_IOC_MOVE_RANGE treats a zero length as a request to move data
from pos_in to EOF. However, the same-file overlap check runs before
that expansion, so a request with len == 0 bypasses the overlap
rejection added for same-file moves.

For example, with a four-block file, moving from block 0 to block 1
with len == 0 is accepted by the old check because pos_in + len is
still pos_in at that point. The code then expands len to cover the
rest of the file and calls __exchange_data_block() on overlapping
source and destination ranges in the same inode, which is the
data-corruption case the overlap check was meant to reject.

Move the overlap check after the source range has been validated and
len == 0 has been expanded, so it sees the effective length. This is a
no-op for non-zero len (the value is unchanged there) and keeps the
existing early return for identical positions.

Fixes: d95fd91c1ac1 ("f2fs: exclude special cases for f2fs_move_file_range")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-fable-5
Signed-off-by: Hao-Qun Huang <alvinhuang0603@gmail.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

0 files changed, 0 insertions, 0 deletions