nfsd4: handle seqid-mutating open errors from xdr decoding

If a client sets an owner (or group_owner or acl) attribute on open for
create, and the mapping of that owner to an id fails, then we return
BAD_OWNER.  But BAD_OWNER is a seqid-mutating error, so we can't
shortcut the open processing that case: we have to at least look up the
owner so we can find the seqid to bump.
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4proc.c

@@ -351,6 +351,10 @@ nfsd4_open(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	}
 	if (status)
 		goto out;
+	if (open->op_xdr_error) {
+		status = open->op_xdr_error;
+		goto out;
+	}
 
 	status = nfsd4_check_open_attributes(rqstp, cstate, open);
 	if (status)
@@ -416,6 +420,24 @@ nfsd4_open(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	return status;
 }
 
+/*
+ * OPEN is the only seqid-mutating operation whose decoding can fail
+ * with a seqid-mutating error (specifically, decoding of user names in
+ * the attributes).  Therefore we have to do some processing to look up
+ * the stateowner so that we can bump the seqid.
+ */
+static __be32 nfsd4_open_omfg(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, struct nfsd4_op *op)
+{
+	struct nfsd4_open *open = (struct nfsd4_open *)&op->u;
+
+	if (!seqid_mutating_err(ntohl(op->status)))
+		return op->status;
+	if (nfsd4_has_session(cstate))
+		return op->status;
+	open->op_xdr_error = op->status;
+	return nfsd4_open(rqstp, cstate, open);
+}
+
 /*
  * filehandle-manipulating ops.
  */
@@ -1244,8 +1266,11 @@ nfsd4_proc_compound(struct svc_rqst *rqstp,
 		 * for example, if there is a miscellaneous XDR error
 		 * it will be set to nfserr_bad_xdr.
 		 */
-		if (op->status)
+		if (op->status) {
+			if (op->opnum == OP_OPEN)
+				op->status = nfsd4_open_omfg(rqstp, cstate, op);
 			goto encode_op;
+		}
 
 		/* We must be able to encode a successful response to
 		 * this operation, with enough room left over to encode a

fs/nfsd/nfs4xdr.c

@@ -804,6 +804,7 @@ nfsd4_decode_open(struct nfsd4_compoundargs *argp, struct nfsd4_open *open)
 	open->op_iattr.ia_valid = 0;
 	open->op_openowner = NULL;
 
+	open->op_xdr_error = 0;
 	/* seqid, share_access, share_deny, clientid, ownerlen */
 	READ_BUF(4);
 	READ32(open->op_seqid);

fs/nfsd/xdr4.h

@@ -237,6 +237,7 @@ struct nfsd4_open {
 	u32		op_share_deny;      /* request */
 	u32		op_deleg_want;      /* request */
 	stateid_t	op_stateid;         /* response */
+	__be32		op_xdr_error;       /* see nfsd4_open_omfg() */
 	u32		op_recall;          /* recall */
 	struct nfsd4_change_info  op_cinfo; /* response */
 	u32		op_rflags;          /* response */