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, 18 insertions, 0 deletions

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index ef583507d276..ebfcebd5eab1 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -2388,6 +2388,22 @@ nfsd4_exchange_id(struct svc_rqst *rqstp,
 
         switch (exid->spa_how) {
         case SP4_MACH_CRED:
+                exid->spo_must_enforce[0] = 0;
+                exid->spo_must_enforce[1] = (
+                        1 << (OP_BIND_CONN_TO_SESSION - 32) |
+                        1 << (OP_EXCHANGE_ID - 32) |
+                        1 << (OP_CREATE_SESSION - 32) |
+                        1 << (OP_DESTROY_SESSION - 32) |
+                        1 << (OP_DESTROY_CLIENTID - 32));
+
+                exid->spo_must_allow[0] &= (1 << (OP_CLOSE) |
+                                        1 << (OP_OPEN_DOWNGRADE) |
+                                        1 << (OP_LOCKU) |
+                                        1 << (OP_DELEGRETURN));
+
+                exid->spo_must_allow[1] &= (
+                                        1 << (OP_TEST_STATEID - 32) |
+                                        1 << (OP_FREE_STATEID - 32));
                 if (!svc_rqst_integrity_protected(rqstp)) {
                         status = nfserr_inval;
                         goto out_nolock;
@@ -2473,6 +2489,8 @@ out_new:
                         goto out;
         }
         new->cl_minorversion = cstate->minorversion;
+        new->cl_spo_must_allow.u.words[0] = exid->spo_must_allow[0];
+        new->cl_spo_must_allow.u.words[1] = exid->spo_must_allow[1];
 
         gen_clid(new, nn);
         add_to_unconfirmed(new);