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, 23 insertions, 28 deletions

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 9df898ba648f..84ef94794496 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1299,16 +1299,14 @@ nfsd4_decode_exchange_id(struct nfsd4_compoundargs *argp,
 		break;
 	case SP4_MACH_CRED:
 		/* spo_must_enforce */
-		READ_BUF(4);
-		dummy = be32_to_cpup(p++);
-		READ_BUF(dummy * 4);
-		p += dummy;
-
+		status = nfsd4_decode_bitmap(argp,
+					exid->spo_must_enforce);
+		if (status)
+			goto out;
 		/* spo_must_allow */
-		READ_BUF(4);
-		dummy = be32_to_cpup(p++);
-		READ_BUF(dummy * 4);
-		p += dummy;
+		status = nfsd4_decode_bitmap(argp, exid->spo_must_allow);
+		if (status)
+			goto out;
 		break;
 	case SP4_SSV:
 		/* ssp_ops */
@@ -3867,14 +3865,6 @@ nfsd4_encode_write(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_w
 	return nfserr;
 }
 
-static const u32 nfs4_minimal_spo_must_enforce[2] = {
-	[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)
-};
-
 static __be32
 nfsd4_encode_exchange_id(struct nfsd4_compoundres *resp, __be32 nfserr,
 			 struct nfsd4_exchange_id *exid)
@@ -3885,6 +3875,7 @@ nfsd4_encode_exchange_id(struct nfsd4_compoundres *resp, __be32 nfserr,
 	char *server_scope;
 	int major_id_sz;
 	int server_scope_sz;
+	int status = 0;
 	uint64_t minor_id = 0;
 
 	if (nfserr)
@@ -3913,18 +3904,20 @@ nfsd4_encode_exchange_id(struct nfsd4_compoundres *resp, __be32 nfserr,
 	case SP4_NONE:
 		break;
 	case SP4_MACH_CRED:
-		/* spo_must_enforce, spo_must_allow */
-		p = xdr_reserve_space(xdr, 16);
-		if (!p)
-			return nfserr_resource;
-
 		/* spo_must_enforce bitmap: */
-		*p++ = cpu_to_be32(2);
-		*p++ = cpu_to_be32(nfs4_minimal_spo_must_enforce[0]);
-		*p++ = cpu_to_be32(nfs4_minimal_spo_must_enforce[1]);
-		/* empty spo_must_allow bitmap: */
-		*p++ = cpu_to_be32(0);
-
+		status = nfsd4_encode_bitmap(xdr,
+					exid->spo_must_enforce[0],
+					exid->spo_must_enforce[1],
+					exid->spo_must_enforce[2]);
+		if (status)
+			goto out;
+		/* spo_must_allow bitmap: */
+		status = nfsd4_encode_bitmap(xdr,
+					exid->spo_must_allow[0],
+					exid->spo_must_allow[1],
+					exid->spo_must_allow[2]);
+		if (status)
+			goto out;
 		break;
 	default:
 		WARN_ON_ONCE(1);
@@ -3951,6 +3944,8 @@ nfsd4_encode_exchange_id(struct nfsd4_compoundres *resp, __be32 nfserr,
 	/* Implementation id */
 	*p++ = cpu_to_be32(0);	/* zero length nfs_impl_id4 array */
 	return 0;
+out:
+	return status;
 }
 
 static __be32