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

[dai.ngo@oracle.com]

On 2/1/21 1:14 PM, Darrick J. Wong wrote:
> 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.

In the ERROR section:

ERROR
	EINVAL Requested range extends beyond the end of the source file; or the flags argument is not 0.

-Dai

>
> --D
>
> [1] https://urldefense.com/v3/__https://man7.org/linux/man-pages/man2/copy_file_range.2.html*RETURN_VALUE__;Iw!!GqivPVa7Brio!N8XGLyK9dUTWOYWmb3NCuq-9kL-tX8OGcq-sV7M53ub5KMgr7e93a2B8eUryKw$
>
>> 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
>>