knfsd: LOOKUP can return an illegal error value

JIRA: https://issues.redhat.com/browse/RHEL-53004

commit e221c45
Author: Trond Myklebust <trond.myklebust@hammerspace.com>
Date:   Mon May 6 12:30:04 2024 -0400

    knfsd: LOOKUP can return an illegal error value

    The 'NFS error' NFSERR_OPNOTSUPP is not described by any of the official
    NFS related RFCs, but appears to have snuck into some older .x files for
    NFSv2.
    Either way, it is not in RFC1094, RFC1813 or any of the NFSv4 RFCs, so
    should not be returned by the knfsd server, and particularly not by the
    "LOOKUP" operation.

    Instead, let's return NFSERR_STALE, which is more appropriate if the
    filesystem encodes the filehandle as FILEID_INVALID.

    Cc: stable@vger.kernel.org
    Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
    Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>

Author: bcodding-rh

fs/nfsd/nfsfh.c

@@ -572,7 +572,7 @@ fh_compose(struct svc_fh *fhp, struct svc_export *exp, struct dentry *dentry,
 		_fh_update(fhp, exp, dentry);
 	if (fhp->fh_handle.fh_fileid_type == FILEID_INVALID) {
 		fh_put(fhp);
-		return nfserr_opnotsupp;
+		return nfserr_stale;
 	}
 
 	return 0;
@@ -598,7 +598,7 @@ fh_update(struct svc_fh *fhp)
 
 	_fh_update(fhp, fhp->fh_export, dentry);
 	if (fhp->fh_handle.fh_fileid_type == FILEID_INVALID)
-		return nfserr_opnotsupp;
+		return nfserr_stale;
 	return 0;
 out_bad:
 	printk(KERN_ERR "fh_update: fh not verified!\n");