nfsd: pass client principal name in rsc downcall

Two principals are involved in krb5 authentication: the target, who we
authenticate *to* (normally the name of the server, like
nfs/server.citi.umich.edu@CITI.UMICH.EDU), and the source, we we
authenticate *as* (normally a user, like bfields@UMICH.EDU)

In the case of NFSv4 callbacks, the target of the callback should be the
source of the client's setclientid call, and the source should be the
nfs server's own principal.

Therefore we allow svcgssd to pass down the name of the principal that
just authenticated, so that on setclientid we can store that principal
name with the new client, to be used later on callbacks.

Signed-off-by: Olga Kornievskaia <aglo@citi.umich.edu>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfsd/nfs4state.c

@@ -54,6 +54,7 @@
 #include <linux/mutex.h>
 #include <linux/lockd/bind.h>
 #include <linux/module.h>
+#include <linux/sunrpc/svcauth_gss.h>
 
 #define NFSDDBG_FACILITY                NFSDDBG_PROC
 
@@ -377,6 +378,7 @@ free_client(struct nfs4_client *clp)
 	shutdown_callback_client(clp);
 	if (clp->cl_cred.cr_group_info)
 		put_group_info(clp->cl_cred.cr_group_info);
+	kfree(clp->cl_principal);
 	kfree(clp->cl_name.data);
 	kfree(clp);
 }
@@ -696,6 +698,7 @@ nfsd4_setclientid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	unsigned int 		strhashval;
 	struct nfs4_client	*conf, *unconf, *new;
 	__be32 			status;
+	char			*princ;
 	char                    dname[HEXDIR_LEN];
 	
 	if (!check_name(clname))
@@ -783,6 +786,14 @@ nfsd4_setclientid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	}
 	copy_verf(new, &clverifier);
 	new->cl_addr = sin->sin_addr.s_addr;
+	princ = svc_gss_principal(rqstp);
+	if (princ) {
+		new->cl_principal = kstrdup(princ, GFP_KERNEL);
+		if (new->cl_principal == NULL) {
+			free_client(new);
+			goto out;
+		}
+	}
 	copy_cred(&new->cl_cred, &rqstp->rq_cred);
 	gen_confirm(new);
 	gen_callback(new, setclid);