nfsd: do nfs4_check_fh in nfs4_check_file instead of nfs4_check_olstateid

commit 8fcd461d upstream.

Currently, preprocess_stateid_op calls nfs4_check_olstateid which
verifies that the open stateid corresponds to the current filehandle in the
call by calling nfs4_check_fh.

If the stateid is a NFS4_DELEG_STID however, then no such check is done.
This could cause incorrect enforcement of permissions, because the
nfsd_permission() call in nfs4_check_file uses current the current
filehandle, but any subsequent IO operation will use the file descriptor
in the stateid.

Move the call to nfs4_check_fh into nfs4_check_file instead so that it
can be done for all stateid types.
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
[bfields: moved fh check to avoid NULL deref in special stateid case]
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/nfsd/nfs4state.c

@@ -4397,9 +4397,9 @@ laundromat_main(struct work_struct *laundry)
 	queue_delayed_work(laundry_wq, &nn->laundromat_work, t*HZ);
 }
 
-static inline __be32 nfs4_check_fh(struct svc_fh *fhp, struct nfs4_ol_stateid *stp)
+static inline __be32 nfs4_check_fh(struct svc_fh *fhp, struct nfs4_stid *stp)
 {
-	if (!fh_match(&fhp->fh_handle, &stp->st_stid.sc_file->fi_fhandle))
+	if (!fh_match(&fhp->fh_handle, &stp->sc_file->fi_fhandle))
 		return nfserr_bad_stateid;
 	return nfs_ok;
 }
@@ -4599,9 +4599,6 @@ nfs4_check_olstateid(struct svc_fh *fhp, struct nfs4_ol_stateid *ols, int flags)
 {
 	__be32 status;
 
-	status = nfs4_check_fh(fhp, ols);
-	if (status)
-		return status;
 	status = nfsd4_check_openowner_confirmed(ols);
 	if (status)
 		return status;
@@ -4652,6 +4649,9 @@ nfs4_preprocess_stateid_op(struct net *net, struct nfsd4_compound_state *cstate,
 		status = nfserr_bad_stateid;
 		break;
 	}
+	if (status)
+		goto out;
+	status = nfs4_check_fh(fhp, s);
 
 	if (!status && filpp) {
 		*filpp = nfs4_find_file(s, flags);
@@ -4761,7 +4761,7 @@ static __be32 nfs4_seqid_op_checks(struct nfsd4_compound_state *cstate, stateid_
 	status = check_stateid_generation(stateid, &stp->st_stid.sc_stateid, nfsd4_has_session(cstate));
 	if (status)
 		return status;
-	return nfs4_check_fh(current_fh, stp);
+	return nfs4_check_fh(current_fh, &stp->st_stid);
 }
 
 /*