SUNRPC: Use namespace of listening daemon in the client AUTH_GSS upcall

When the client needs to talk to rpc.gssd, we should ensure that the
uid argument is encoded to match the user namespace of the daemon.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/auth_gss/auth_gss.c

@@ -269,6 +269,7 @@ gss_fill_context(const void *p, const void *end, struct gss_cl_ctx *ctx, struct
 struct gss_upcall_msg {
 	refcount_t count;
 	kuid_t	uid;
+	const char *service_name;
 	struct rpc_pipe_msg msg;
 	struct list_head list;
 	struct gss_auth *auth;
@@ -316,6 +317,7 @@ gss_release_msg(struct gss_upcall_msg *gss_msg)
 		gss_put_ctx(gss_msg->ctx);
 	rpc_destroy_wait_queue(&gss_msg->rpc_waitqueue);
 	gss_put_auth(gss_msg->auth);
+	kfree_const(gss_msg->service_name);
 	kfree(gss_msg);
 }
 
@@ -410,10 +412,10 @@ gss_upcall_callback(struct rpc_task *task)
 	gss_release_msg(gss_msg);
 }
 
-static void gss_encode_v0_msg(struct gss_upcall_msg *gss_msg)
+static void gss_encode_v0_msg(struct gss_upcall_msg *gss_msg,
+			      const struct cred *cred)
 {
-	struct user_namespace *userns = gss_msg->auth->client->cl_cred ?
-		gss_msg->auth->client->cl_cred->user_ns : &init_user_ns;
+	struct user_namespace *userns = cred->user_ns;
 
 	uid_t uid = from_kuid_munged(userns, gss_msg->uid);
 	memcpy(gss_msg->databuf, &uid, sizeof(uid));
@@ -423,12 +425,24 @@ static void gss_encode_v0_msg(struct gss_upcall_msg *gss_msg)
 	BUILD_BUG_ON(sizeof(uid) > sizeof(gss_msg->databuf));
 }
 
+static ssize_t
+gss_v0_upcall(struct file *file, struct rpc_pipe_msg *msg,
+		char __user *buf, size_t buflen)
+{
+	struct gss_upcall_msg *gss_msg = container_of(msg,
+						      struct gss_upcall_msg,
+						      msg);
+	if (msg->copied == 0)
+		gss_encode_v0_msg(gss_msg, file->f_cred);
+	return rpc_pipe_generic_upcall(file, msg, buf, buflen);
+}
+
 static int gss_encode_v1_msg(struct gss_upcall_msg *gss_msg,
 				const char *service_name,
-				const char *target_name)
+				const char *target_name,
+				const struct cred *cred)
 {
-	struct user_namespace *userns = gss_msg->auth->client->cl_cred ?
-		gss_msg->auth->client->cl_cred->user_ns : &init_user_ns;
+	struct user_namespace *userns = cred->user_ns;
 	struct gss_api_mech *mech = gss_msg->auth->mech;
 	char *p = gss_msg->databuf;
 	size_t buflen = sizeof(gss_msg->databuf);
@@ -496,6 +510,25 @@ static int gss_encode_v1_msg(struct gss_upcall_msg *gss_msg,
 	return -ENOMEM;
 }
 
+static ssize_t
+gss_v1_upcall(struct file *file, struct rpc_pipe_msg *msg,
+		char __user *buf, size_t buflen)
+{
+	struct gss_upcall_msg *gss_msg = container_of(msg,
+						      struct gss_upcall_msg,
+						      msg);
+	int err;
+	if (msg->copied == 0) {
+		err = gss_encode_v1_msg(gss_msg,
+					gss_msg->service_name,
+					gss_msg->auth->target_name,
+					file->f_cred);
+		if (err)
+			return err;
+	}
+	return rpc_pipe_generic_upcall(file, msg, buf, buflen);
+}
+
 static struct gss_upcall_msg *
 gss_alloc_msg(struct gss_auth *gss_auth,
 		kuid_t uid, const char *service_name)
@@ -518,16 +551,11 @@ gss_alloc_msg(struct gss_auth *gss_auth,
 	refcount_set(&gss_msg->count, 1);
 	gss_msg->uid = uid;
 	gss_msg->auth = gss_auth;
-	switch (vers) {
-	case 0:
-		gss_encode_v0_msg(gss_msg);
-		break;
-	default:
-		err = gss_encode_v1_msg(gss_msg, service_name, gss_auth->target_name);
-		if (err)
+	if (service_name) {
+		gss_msg->service_name = kstrdup_const(service_name, GFP_NOFS);
+		if (!gss_msg->service_name)
 			goto err_put_pipe_version;
 	}
-	kref_get(&gss_auth->kref);
 	return gss_msg;
 err_put_pipe_version:
 	put_pipe_version(gss_auth->net);
@@ -2120,7 +2148,7 @@ static const struct rpc_credops gss_nullops = {
 };
 
 static const struct rpc_pipe_ops gss_upcall_ops_v0 = {
-	.upcall		= rpc_pipe_generic_upcall,
+	.upcall		= gss_v0_upcall,
 	.downcall	= gss_pipe_downcall,
 	.destroy_msg	= gss_pipe_destroy_msg,
 	.open_pipe	= gss_pipe_open_v0,
@@ -2128,7 +2156,7 @@ static const struct rpc_pipe_ops gss_upcall_ops_v0 = {
 };
 
 static const struct rpc_pipe_ops gss_upcall_ops_v1 = {
-	.upcall		= rpc_pipe_generic_upcall,
+	.upcall		= gss_v1_upcall,
 	.downcall	= gss_pipe_downcall,
 	.destroy_msg	= gss_pipe_destroy_msg,
 	.open_pipe	= gss_pipe_open_v1,