Re: [PATCH] f2fs: reject overlapping move range after len expansion

[Chao Yu <chao@kernel.org>]

On 7/8/26 14:54, Hao-Qun Huang wrote:
> 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>
> ---
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 4b52c56d71f0..fdfef01dc799 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -3144,8 +3144,6 @@ static int f2fs_move_file_range(struct file *file_in, loff_t pos_in,
>   	if (src == dst) {
>   		if (pos_in == pos_out)
>   			return 0;
> -		if (pos_out > pos_in && pos_out < pos_in + len)
> -			return -EINVAL;
>   	}
>   
>   	inode_lock(src);
> @@ -3171,6 +3169,8 @@ static int f2fs_move_file_range(struct file *file_in, loff_t pos_in,
>   		goto out_unlock;
>   	if (len == 0)
>   		olen = len = src->i_size - pos_in;
> +	if (src == dst && pos_out > pos_in && pos_out < pos_in + len)
> +		goto out_unlock;

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,

>   	if (pos_in + len == src->i_size)
>   		len = ALIGN(src->i_size, F2FS_BLKSIZE) - pos_in;
>   	if (len == 0) {