On Thu, Sep 14, 2017 at 9:47 PM, J. Bruce Fields <bfields@xxxxxxxxxx> wrote:
> On Thu, Sep 14, 2017 at 02:44:32PM -0400, Olga Kornievskaia wrote:
>> How about changing it to be more restrictive by checking within the
>> while loop that
>> if it's a PUTFH and it's followed by the SAVE_FH+PUTFH+COPY only
>> then set the NO_VERIFY_FH.
>
> I agree that the only op that could reasonably follow the first PUTFH of
> a foreign filehandle is a SAVEFH. But once we've saved the foreign
> filehandle, the client could in theory do all sorts of stuff, as you
> say:
>
>> I guess we can allow some other operations between the 2nd PUTFH and
>> COPY because the 2nd filehandle will be validated and must be valid to
>> continue processing the compound.
>
> PUTHF+SAVEFH+PUTFH+GETATTR+COPY might be useful to get pre-copy
> attributes of the target file, for example?
>
> I'd rather not restrict this if we don't need to.
>
> We could do something like:
>
> - if this op is PUTFH
> - if the following is not SAVEFH, stop and verify the
> filehandle.
> - otherwise, skip to the next operation that uses a saved
> filehandle. The possibilities are:
> - RENAME, LINK, RESTOREFH, CLONE: stop and verify the
> filehandle.
> - COPY: if it's a local copy, stop and verify the
> filehandle. Otherwise, allow the PUTFH to succeed and
> delay verification.
OK so I can peep into the upcoming copy and see if it's inter or intra and
then based on that I can set NO_VERIFY_FH for processing the putfh.
>> Somewhere else you were talking about how a "foreign" file handle can
>> mean something to the server. If that's the case and we do allow for
>> operations between putfh, savefh, putfh then we'll get into trouble
>> that I can't think we can get out of.
>>
>> If it's a inter copy and the source file handle means something to the
>> server I can think of the following scenario: the state won't be
>> flagged IS_STALE then the filehandle would go thru the checks you
>> listed below and can (unintentionally) result in an error (eg.,
>> err_moved?).
>
> I don't see any problem with just leaving those checks in. If the
> current filehandle is not validated, then there's already a
> current_fh->fh_dentry check that skips the ABSENT_FH check, for example.
>
>> This should be changed to
>> if (HAS_CSTATE_FLAG(cstate, IS_STALE_FH) && op->opnum == OP_SAVEFH)
>> then we need to skip the checks for savefh as it has no valid file handle.
>>
>> Does that address your concern?
>
> I think you only need to skip the nofilehandle check in this case, not
> the other stuff.
As long as I can add that current_fh->fh_export is not null for the 2nd check
otherwise it leads to an oops.
> I don't think the IS_STALE_FH flag is needed at all.
We still need it so that the savefh process can skip the check for the
filehandle.
Or I can use something like checking that fh_dentry and fh_export are both null
and use that to mean I need to check the filehandle check in savefh.
I think explicitly marking it makes the code either to understand instead of
'knowning/remembering' that lack of fh_dentry+fh_export means inter copy?
>> >> if (!current_fh->fh_dentry) {
>> >> if (!(opdesc->op_flags & ALLOWED_WITHOUT_FH)) {
>> >> op->status = nfserr_nofilehandle;
>> >> @@ -1844,6 +1880,7 @@ static void svcxdr_init_encode(struct svc_rqst *rqstp,
>> >>
>> >> if (opdesc->op_get_currentstateid)
>> >> opdesc->op_get_currentstateid(cstate, &op->u);
>> >> +call_op:
>> >> op->status = opdesc->op_func(rqstp, cstate, &op->u);
>> >>
>> >> /* Only from SEQUENCE */
>> >> @@ -1862,6 +1899,14 @@ static void svcxdr_init_encode(struct svc_rqst *rqstp,
>> >> if (need_wrongsec_check(rqstp))
>> >> op->status = check_nfsd_access(current_fh->fh_export, rqstp);
>> >> }
>> >> + /* Only from intra COPY */
>> >> + if (cstate->status == nfserr_copy_stalefh) {
>> >> + dprintk("%s NFS4.2 intra COPY stale src filehandle\n",
>> >> + __func__);
>> >> + status = nfserr_stale;
>> >> + nfsd4_adjust_encode(resp);
>> >
>> > Are you sure it's safe just to throw away any operations since that
>> > stale PUTFH? What if some of those operations had side effects?
>>
>> If COPY comes in PUTFH,SAVEFH, PUTFH,COPY compound then
>> I think it's safe?
>
> The spec says "If a server supports the inter-server copy feature, a
> PUTFH followed by a SAVEFH MUST NOT return NFS4ERR_STALE for either
> operation. These restrictions do not pose substantial difficulties for
> servers. CURRENT_FH and SAVED_FH may be validated in the context of the
> operation referencing them and an NFS4ERR_STALE error returned for an
> invalid filehandle at that point."
>
> So we're supposed to return NFS4ERR_STALE on the COPY, not the PUTFH.
> So there's no need for this backtracking.
You are right.
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