machined: when reading os-release file, join PID namespace too

This is required for /proc/self/fd/xyz to work, but that's what we need
to convert the O_PATH fd returned by chase_symlinks() back to a regular
file fd. Hence, let's do the joining of the namespaces fully and
correctly, by doing fork()+setns()+fork() with the PID and fs
namespaces.

This makes use of the new namespace_fork() helper we just added.

Fixes: #10549

diff --git a/src/machine/machine-dbus.c b/src/machine/machine-dbus.c
index 4f4d780db0f866a6bf97d02dc53524f4103e78e7..4cdfaed45554e52991b2029b03c3d4f8a6b81486 100644 (file)
--- a/src/machine/machine-dbus.c
+++ b/src/machine/machine-dbus.c
@@ -333,19 +333,21 @@ int bus_machine_method_get_os_release(sd_bus_message *message, void *userdata, s
                 break;
 
         case MACHINE_CONTAINER: {
-                _cleanup_close_ int mntns_fd = -1, root_fd = -1;
+                _cleanup_close_ int mntns_fd = -1, root_fd = -1, pidns_fd = -1;
                 _cleanup_close_pair_ int pair[2] = { -1, -1 };
                 _cleanup_fclose_ FILE *f = NULL;
                 pid_t child;
 
-                r = namespace_open(m->leader, NULL, &mntns_fd, NULL, NULL, &root_fd);
+                r = namespace_open(m->leader, &pidns_fd, &mntns_fd, NULL, NULL, &root_fd);
                 if (r < 0)
                         return r;
 
                 if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, pair) < 0)
                         return -errno;
 
-                r = safe_fork("(sd-osrel)", FORK_RESET_SIGNALS|FORK_DEATHSIG, &child);
+                r = namespace_fork("(sd-osrelns)", "(sd-osrel)", NULL, 0, FORK_RESET_SIGNALS|FORK_DEATHSIG,
+                                   pidns_fd, mntns_fd, -1, -1, root_fd,
+                                   &child);
                 if (r < 0)
                         return sd_bus_error_set_errnof(error, r, "Failed to fork(): %m");
                 if (r == 0) {
@@ -353,10 +355,6 @@ int bus_machine_method_get_os_release(sd_bus_message *message, void *userdata, s
 
                         pair[0] = safe_close(pair[0]);
 
-                        r = namespace_enter(-1, mntns_fd, -1, -1, root_fd);
-                        if (r < 0)
-                                _exit(EXIT_FAILURE);
-
                         r = open_os_release(NULL, NULL, &fd);
                         if (r == -ENOENT)
                                 _exit(EXIT_NOT_FOUND);
@@ -382,7 +380,7 @@ int bus_machine_method_get_os_release(sd_bus_message *message, void *userdata, s
                 if (r < 0)
                         return r;
 
-                r = wait_for_terminate_and_check("(sd-osrel)", child, 0);
+                r = wait_for_terminate_and_check("(sd-osrelns)", child, 0);
                 if (r < 0)
                         return sd_bus_error_set_errnof(error, r, "Failed to wait for child: %m");
                 if (r == EXIT_NOT_FOUND)