NFSv4: Reintroduce machine creds

We need to try to ensure that we always use the same credentials whenever
we re-establish the clientid on the server. If not, the server won't
recognise that we're the same client, and so may not allow us to recover
state.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 35 insertions, 3 deletions

diff --git a/net/sunrpc/auth_generic.c b/net/sunrpc/auth_generic.c
index b6f124c85072..d927d9f57412 100644
--- a/net/sunrpc/auth_generic.c
+++ b/net/sunrpc/auth_generic.c
@@ -17,6 +17,9 @@
 # define RPCDBG_FACILITY        RPCDBG_AUTH
 #endif
 
+#define RPC_ANONYMOUS_USERID    ((uid_t)-2)
+#define RPC_ANONYMOUS_GROUPID   ((gid_t)-2)
+
 struct generic_cred {
         struct rpc_cred gc_base;
         struct auth_cred acred;
@@ -35,6 +38,22 @@ struct rpc_cred *rpc_lookup_cred(void)
 }
 EXPORT_SYMBOL_GPL(rpc_lookup_cred);
 
+/*
+ * Public call interface for looking up machine creds.
+ */
+struct rpc_cred *rpc_lookup_machine_cred(void)
+{
+        struct auth_cred acred = {
+                .uid = RPC_ANONYMOUS_USERID,
+                .gid = RPC_ANONYMOUS_GROUPID,
+                .machine_cred = 1,
+        };
+
+        dprintk("RPC:       looking up machine cred\n");
+        return generic_auth.au_ops->lookup_cred(&generic_auth, &acred, 0);
+}
+EXPORT_SYMBOL_GPL(rpc_lookup_machine_cred);
+
 static void
 generic_bind_cred(struct rpc_task *task, struct rpc_cred *cred)
 {
@@ -75,8 +94,10 @@ generic_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
         gcred->acred.group_info = acred->group_info;
         if (gcred->acred.group_info != NULL)
                 get_group_info(gcred->acred.group_info);
+        gcred->acred.machine_cred = acred->machine_cred;
 
-        dprintk("RPC:       allocated generic cred %p for uid %d gid %d\n",
+        dprintk("RPC:       allocated %s cred %p for uid %d gid %d\n",
+                        gcred->acred.machine_cred ? "machine" : "generic",
                         gcred, acred->uid, acred->gid);
         return &gcred->gc_base;
 }
@@ -115,7 +136,8 @@ generic_match(struct auth_cred *acred, struct rpc_cred *cred, int flags)
 
         if (gcred->acred.uid != acred->uid ||
             gcred->acred.gid != acred->gid ||
-            gcred->acred.group_info != acred->group_info)
+            gcred->acred.group_info != acred->group_info ||
+            gcred->acred.machine_cred != acred->machine_cred)
                 return 0;
         return 1;
 }
diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index 7567eb95823b..46f7ec800af9 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -371,9 +371,16 @@ gss_alloc_msg(struct gss_auth *gss_auth, uid_t uid)
 static struct gss_upcall_msg *
 gss_setup_upcall(struct rpc_clnt *clnt, struct gss_auth *gss_auth, struct rpc_cred *cred)
 {
+        struct gss_cred *gss_cred = container_of(cred,
+                        struct gss_cred, gc_base);
         struct gss_upcall_msg *gss_new, *gss_msg;
+        uid_t uid = cred->cr_uid;
 
-        gss_new = gss_alloc_msg(gss_auth, cred->cr_uid);
+        /* Special case: rpc.gssd assumes that uid == 0 implies machine creds */
+        if (gss_cred->gc_machine_cred != 0)
+                uid = 0;
+
+        gss_new = gss_alloc_msg(gss_auth, uid);
         if (gss_new == NULL)
                 return ERR_PTR(-ENOMEM);
         gss_msg = gss_add_msg(gss_auth, gss_new);
@@ -818,6 +825,7 @@ gss_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
          */
         cred->gc_base.cr_flags = 1UL << RPCAUTH_CRED_NEW;
         cred->gc_service = gss_auth->service;
+        cred->gc_machine_cred = acred->machine_cred;
         kref_get(&gss_auth->kref);
         return &cred->gc_base;
 
@@ -855,6 +863,8 @@ gss_match(struct auth_cred *acred, struct rpc_cred *rc, int flags)
         if (gss_cred->gc_ctx && time_after(jiffies, gss_cred->gc_ctx->gc_expiry))
                 return 0;
 out:
+        if (acred->machine_cred != gss_cred->gc_machine_cred)
+                return 0;
         return (rc->cr_uid == acred->uid);
 }