2 files changed, 32 insertions, 5 deletions

diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
index c2e9cfd9e5a4..3e634f2a1083 100644
--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -16,6 +16,7 @@
 #include <linux/mutex.h>
 #include <linux/freezer.h>
 #include <linux/kthread.h>
+#include <linux/sunrpc/svcauth_gss.h>
 
 #include <net/inet_sock.h>
 
@@ -182,10 +183,34 @@ void nfs_callback_down(void)
         mutex_unlock(&nfs_callback_mutex);
 }
 
+static int check_gss_callback_principal(struct nfs_client *clp,
+                                        struct svc_rqst *rqstp)
+{
+        struct rpc_clnt *r = clp->cl_rpcclient;
+        char *p = svc_gss_principal(rqstp);
+
+        /*
+         * It might just be a normal user principal, in which case
+         * userspace won't bother to tell us the name at all.
+         */
+        if (p == NULL)
+                return SVC_DENIED;
+
+        /* Expect a GSS_C_NT_HOSTBASED_NAME like "nfs@serverhostname" */
+
+        if (memcmp(p, "nfs@", 4) != 0)
+                return SVC_DENIED;
+        p += 4;
+        if (strcmp(p, r->cl_server) != 0)
+                return SVC_DENIED;
+        return SVC_OK;
+}
+
 static int nfs_callback_authenticate(struct svc_rqst *rqstp)
 {
         struct nfs_client *clp;
         RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);
+        int ret = SVC_OK;
 
         /* Don't talk to strangers */
         clp = nfs_find_client(svc_addr(rqstp), 4);
@@ -194,21 +219,22 @@ static int nfs_callback_authenticate(struct svc_rqst *rqstp)
 
         dprintk("%s: %s NFSv4 callback!\n", __func__,
                         svc_print_addr(rqstp, buf, sizeof(buf)));
-        nfs_put_client(clp);
 
         switch (rqstp->rq_authop->flavour) {
                 case RPC_AUTH_NULL:
                         if (rqstp->rq_proc != CB_NULL)
-                                return SVC_DENIED;
+                                ret = SVC_DENIED;
                         break;
                 case RPC_AUTH_UNIX:
                         break;
                 case RPC_AUTH_GSS:
-                        /* FIXME: RPCSEC_GSS handling? */
+                        ret = check_gss_callback_principal(clp, rqstp);
+                        break;
                 default:
-                        return SVC_DENIED;
+                        ret = SVC_DENIED;
         }
-        return SVC_OK;
+        nfs_put_client(clp);
+        return ret;
 }
 
 /*
diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index e9baa6ebb1dd..2278a50c6444 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -935,6 +935,7 @@ char *svc_gss_principal(struct svc_rqst *rqstp)
                 return gd->rsci->client_name;
         return NULL;
 }
+EXPORT_SYMBOL_GPL(svc_gss_principal);
 
 static int
 svcauth_gss_set_client(struct svc_rqst *rqstp)