Re: [PATCH 1/1] NFSD: detect mismatch of file handle and delegation stateid in OPEN op

[Dai Ngo <dai.ngo@oracle.com>]

On 6/10/25 7:01 AM, Chuck Lever wrote:
> On 6/10/25 9:59 AM, Jeff Layton wrote:
>> On Tue, 2025-06-10 at 09:52 -0400, Chuck Lever wrote:
>>> On 6/10/25 9:50 AM, Jeff Layton wrote:
>>>> On Tue, 2025-06-10 at 06:41 -0700, Dai Ngo wrote:
>>>>> When the client sends an OPEN with claim type CLAIM_DELEG_CUR_FH or
>>>>> CLAIM_DELEGATION_CUR, the delegation stateid and the file handle
>>>>> must belongs to the same file, otherwise return NFS4ERR_BAD_STATEID.
>>>>>
>>>>> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
>>>>> ---
>>>>>   fs/nfsd/nfs4state.c | 5 +++++
>>>>>   1 file changed, 5 insertions(+)
>>>>>
>>>>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>>>>> index 59a693f22452..be2ee641a22d 100644
>>>>> --- a/fs/nfsd/nfs4state.c
>>>>> +++ b/fs/nfsd/nfs4state.c
>>>>> @@ -6318,6 +6318,11 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
>>>>>   		status = nfs4_check_deleg(cl, open, &dp);
>>>>>   		if (status)
>>>>>   			goto out;
>>>>> +		if (dp && nfsd4_is_deleg_cur(open) &&
>>>>> +				(dp->dl_stid.sc_file != fp)) {
>>>>> +			status = nfserr_bad_stateid;
>>>>> +			goto out;
>>>>> +		}
>>>>>   		stp = nfsd4_find_and_lock_existing_open(fp, open);
>>>>>   	} else {
>>>>>   		open->op_file = NULL;
>>>> This seems like a good idea. I wonder if BAD_STATEID is the right error
>>>> here. It is a valid stateid, after all, it just doesn't match the
>>>> current_fh. Maybe this should be nfserr_inval ?
>>> I agree, NFS4ERR_BAD_STATEID /might/ cause a loop, so that needs to be
>>> tested. BAD_STATEID is mandated by the spec, so if we choose to return
>>> a different status code here, it needs a comment explaining why.
>>>
>> Oh, I didn't realize that error was mandated, but you're right.
>> RFC8881, section 8.2.4:
>>
>> - If the selected table entry does not match the current filehandle,
>> return NFS4ERR_BAD_STATEID.
>>
>> I guess we're stuck with reporting that unless we want to amend the
>> spec.
> It is spec-mandated behavior, but we are always free to ignore the
> spec. I'm OK with NFS4ERR_INVAL if it results in better behavior
> (as long as there is a comment explaining why we deviate from the
> mandate).

Since the Linux client does not behave this way I can not test if this
error get us into a loop. I used pynfs to force this behavior.

However, here is the comment in nfs4_do_open:

                 /*
                  * BAD_STATEID on OPEN means that the server cancelled our
                  * state before it received the OPEN_CONFIRM.
                  * Recover by retrying the request as per the discussion
                  * on Page 181 of RFC3530.
                  */

So it guess BAD_STATEID will  get the client and server into a loop.
I'll change error to NFS4ERR_INVAL and add a comment in the code.

-Dai

>
>
>>>> In any case, whatever we decide:
>>>>
>>>> Reviewed-by: Jeff Layton <jlayton@kernel.org>
>