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>

1 files changed, 11 insertions, 1 deletions

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);
 }