nfsd: implement machine credential support for some operations

This addresses the conundrum referenced in RFC5661 18.35.3,
and will allow clients to return state to the server using the
machine credentials.

The biggest part of the problem is that we need to allow the client
to send a compound op with integrity/privacy on mounts that don't
have it enabled.

Add server support for properly decoding and using spo_must_enforce
and spo_must_allow bits. Add support for machine credentials to be
used for CLOSE, OPEN_DOWNGRADE, LOCKU, DELEGRETURN,
and TEST/FREE STATEID.
Implement a check so as to not throw WRONGSEC errors when these
operations are used if integrity/privacy isn't turned on.

Without this, Linux clients with credentials that expired while holding
delegations were getting stuck in an endless loop.

Signed-off-by: Andrew Elble <aweits@rit.edu>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index de1ff1d98bb1..b1159b3e9816 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -2335,6 +2335,45 @@ static struct nfsd4_operation nfsd4_ops[] = {
 	},
 };
 
+/**
+ * nfsd4_spo_must_allow - Determine if the compound op contains an
+ * operation that is allowed to be sent with machine credentials
+ *
+ * @rqstp: a pointer to the struct svc_rqst
+ *
+ * Checks to see if the compound contains a spo_must_allow op
+ * and confirms that it was sent with the proper machine creds.
+ */
+
+bool nfsd4_spo_must_allow(struct svc_rqst *rqstp)
+{
+	struct nfsd4_compoundres *resp = rqstp->rq_resp;
+	struct nfsd4_compoundargs *argp = rqstp->rq_argp;
+	struct nfsd4_op *this = &argp->ops[resp->opcnt - 1];
+	struct nfsd4_compound_state *cstate = &resp->cstate;
+	struct nfs4_op_map *allow = &cstate->clp->cl_spo_must_allow;
+	u32 opiter;
+
+	if (!cstate->minorversion)
+		return false;
+
+	if (cstate->spo_must_allowed == true)
+		return true;
+
+	opiter = resp->opcnt;
+	while (opiter < argp->opcnt) {
+		this = &argp->ops[opiter++];
+		if (test_bit(this->opnum, allow->u.longs) &&
+			cstate->clp->cl_mach_cred &&
+			nfsd4_mach_creds_match(cstate->clp, rqstp)) {
+			cstate->spo_must_allowed = true;
+			return true;
+		}
+	}
+	cstate->spo_must_allowed = false;
+	return false;
+}
+
 int nfsd4_max_reply(struct svc_rqst *rqstp, struct nfsd4_op *op)
 {
 	struct nfsd4_operation *opdesc;