From 354bfd2b166d1044eea05ac9ba1cda05c93a24bc Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 9 Jan 2014 08:42:57 +0800
Subject: [PATCH] nspawn: do not invoke RegisterMachine on machined from inside
 the new PID namespace

On kdbus user credentials are not translated across PID namespaces, but
simply invalidated if sender and receiver namespaces don't match. This
makes it impossible to properly authenticate requests from different PID
namespaces (which is probably a good thing). Hence, register the machine
in the parent and not the client and properly synchronize this.
---
 src/nspawn/nspawn.c | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 241b4b539..caf1aa9be 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -40,6 +40,7 @@
 #include <sys/un.h>
 #include <sys/socket.h>
 #include <linux/netlink.h>
+#include <sys/eventfd.h>
 
 #include "sd-daemon.h"
 #include "sd-bus.h"
@@ -996,7 +997,7 @@ static int drop_capabilities(void) {
         return capability_bounding_set_drop(~arg_retain, false);
 }
 
-static int register_machine(void) {
+static int register_machine(pid_t pid) {
         _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
         _cleanup_bus_unref_ sd_bus *bus = NULL;
         int r;
@@ -1020,7 +1021,7 @@ static int register_machine(void) {
                         SD_BUS_MESSAGE_APPEND_ID128(arg_uuid),
                         "nspawn",
                         "container",
-                        (uint32_t) 0,
+                        (uint32_t) pid,
                         strempty(arg_directory),
                         !isempty(arg_slice), "Slice", "s", arg_slice);
         if (r < 0) {
@@ -1097,7 +1098,7 @@ static bool audit_enabled(void) {
 int main(int argc, char *argv[]) {
         pid_t pid = 0;
         int r = EXIT_FAILURE, k;
-        _cleanup_close_ int master = -1, kdbus_fd = -1;
+        _cleanup_close_ int master = -1, kdbus_fd = -1, sync_fd = -1;
         int n_fd_passed;
         const char *console = NULL;
         sigset_t mask;
@@ -1213,7 +1214,13 @@ int main(int argc, char *argv[]) {
                 log_debug("Successfully created kdbus namespace as %s", kdbus_namespace);
 
         if (socketpair(AF_UNIX, SOCK_DGRAM|SOCK_NONBLOCK|SOCK_CLOEXEC, 0, kmsg_socket_pair) < 0) {
-                log_error("Failed to create kmsg socket pair.");
+                log_error("Failed to create kmsg socket pair: %m");
+                goto finish;
+        }
+
+        sync_fd = eventfd(0, EFD_CLOEXEC);
+        if (sync_fd < 0) {
+                log_error("Failed to create event fd: %m");
                 goto finish;
         }
 
@@ -1255,6 +1262,7 @@ int main(int argc, char *argv[]) {
                                 NULL
                         };
                         char **env_use;
+                        eventfd_t x;
 
                         envp[n_env] = strv_find_prefix(environ, "TERM=");
                         if (envp[n_env])
@@ -1302,10 +1310,6 @@ int main(int argc, char *argv[]) {
                                 goto child_fail;
                         }
 
-                        r = register_machine();
-                        if (r < 0)
-                                goto finish;
-
                         /* Mark everything as slave, so that we still
                          * receive mounts from the real root, but don't
                          * propagate mounts to the real root. */
@@ -1482,6 +1486,10 @@ int main(int argc, char *argv[]) {
 
                         setup_hostname();
 
+                        eventfd_read(sync_fd, &x);
+                        close_nointr_nofail(sync_fd);
+                        sync_fd = -1;
+
                         if (!strv_isempty(arg_setenv)) {
                                 char **n;
 
@@ -1529,6 +1537,14 @@ int main(int argc, char *argv[]) {
                 fdset_free(fds);
                 fds = NULL;
 
+                r = register_machine(pid);
+                if (r < 0)
+                        goto finish;
+
+                eventfd_write(sync_fd, 1);
+                close_nointr_nofail(sync_fd);
+                sync_fd = -1;
+
                 k = process_pty(master, &mask, arg_boot ? pid : 0, SIGRTMIN+3);
                 if (k < 0) {
                         r = EXIT_FAILURE;
-- 
2.30.2