Re: [PATCH v2] vfs: generic_copy_file_checks should return EINVAL when source offset is beyond EOF

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Feb 01, 2021 at 03:49:52PM -0500, Dai Ngo wrote:
> Fix by returning -EINVAL instead of 0, per man page of copy_file_range,

Huh?  That's not what the manpage[1] says:

RETURN VALUE
       Upon successful completion, copy_file_range() will return the
number of bytes copied between files.  This could be less than the
length originally requested.  If the file offset of fd_in is at or past
the end of file, no bytes are copied, and copy_file_range() returns
zero.

--D

[1] https://man7.org/linux/man-pages/man2/copy_file_range.2.html#RETURN_VALUE

> when the requested range extends beyond the end of the source file.
> Problem was discovered by subtest inter11 of nfstest_ssc.
> 
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
>  fs/read_write.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 75f764b43418..438c00910716 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1445,7 +1445,7 @@ static int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
>  	/* Shorten the copy to EOF */
>  	size_in = i_size_read(inode_in);
>  	if (pos_in >= size_in)
> -		count = 0;
> +		count = -EINVAL;
>  	else
>  		count = min(count, size_in - (uint64_t)pos_in);
>  
> -- 
> 2.9.5
>