console: only create detached mount when a console is requested

otherwise weird things might happen.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index 3753fd7a626b44398108c9983f47f0b80b3d5585..e2e2f9e97a44894e2571cb37ceb599d7196354ae 100644 (file)
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -1575,6 +1575,11 @@ static int setup_personality(int persona)
        return 0;
 }
 
+static inline bool wants_console(const struct lxc_terminal *terminal)
+{
+       return !terminal->path || strcmp(terminal->path, "none");
+}
+
 static int lxc_setup_dev_console(const struct lxc_rootfs *rootfs,
                                 const struct lxc_terminal *console,
                                 int pts_mnt_fd)
@@ -1583,7 +1588,7 @@ static int lxc_setup_dev_console(const struct lxc_rootfs *rootfs,
        char path[PATH_MAX];
        char *rootfs_path = rootfs->path ? rootfs->mount : "";
 
-       if (console->path && !strcmp(console->path, "none"))
+       if (!wants_console(console))
                return 0;
 
        ret = snprintf(path, sizeof(path), "%s/dev/console", rootfs_path);
@@ -1614,13 +1619,24 @@ static int lxc_setup_dev_console(const struct lxc_rootfs *rootfs,
        if (ret < 0)
                return log_error_errno(-errno, errno, "Failed to set mode \"0%o\" to \"%s\"", S_IXUSR | S_IXGRP, console->name);
 
-       if (pts_mnt_fd >= 0)
+       if (pts_mnt_fd >= 0) {
                ret = move_mount(pts_mnt_fd, "", -EBADF, path, MOVE_MOUNT_F_EMPTY_PATH);
-       else
-               ret = safe_mount(console->name, path, "none", MS_BIND, 0, rootfs_path);
+               if (!ret) {
+                       DEBUG("Moved mount \"%s\" onto \"%s\"", console->name, path);
+                       goto finish;
+               }
+
+               if (ret && errno != ENOSYS)
+                       return log_error_errno(-1, errno,
+                                              "Failed to mount %d(%s) on \"%s\"",
+                                              pts_mnt_fd, console->name, path);
+       }
+
+       ret = safe_mount(console->name, path, "none", MS_BIND, 0, rootfs_path);
        if (ret < 0)
                return log_error_errno(-1, errno, "Failed to mount %d(%s) on \"%s\"", pts_mnt_fd, console->name, path);
 
+finish:
        DEBUG("Mounted pts device %d(%s) onto \"%s\"", pts_mnt_fd, console->name, path);
        return 0;
 }
@@ -1633,7 +1649,7 @@ static int lxc_setup_ttydir_console(const struct lxc_rootfs *rootfs,
        char path[PATH_MAX], lxcpath[PATH_MAX];
        char *rootfs_path = rootfs->path ? rootfs->mount : "";
 
-       if (console->path && !strcmp(console->path, "none"))
+       if (!wants_console(console))
                return 0;
 
        /* create rootfs/dev/<ttydir> directory */
@@ -1675,14 +1691,25 @@ static int lxc_setup_ttydir_console(const struct lxc_rootfs *rootfs,
                return log_error_errno(-errno, errno, "Failed to set mode \"0%o\" to \"%s\"", S_IXUSR | S_IXGRP, console->name);
 
        /* bind mount console->name to '/dev/<ttydir>/console' */
-       if (pts_mnt_fd >= 0)
-               ret = move_mount(pts_mnt_fd, "", -EBADF, path, MOVE_MOUNT_F_EMPTY_PATH);
-       else
-               ret = safe_mount(console->name, lxcpath, "none", MS_BIND, 0, rootfs_path);
+       if (pts_mnt_fd >= 0) {
+               ret = move_mount(pts_mnt_fd, "", -EBADF, lxcpath, MOVE_MOUNT_F_EMPTY_PATH);
+               if (!ret) {
+                       DEBUG("Moved mount \"%s\" onto \"%s\"", console->name, lxcpath);
+                       goto finish;
+               }
+
+               if (ret && errno != ENOSYS)
+                       return log_error_errno(-1, errno,
+                                              "Failed to mount %d(%s) on \"%s\"",
+                                              pts_mnt_fd, console->name, lxcpath);
+       }
+
+       ret = safe_mount(console->name, lxcpath, "none", MS_BIND, 0, rootfs_path);
        if (ret < 0)
                return log_error_errno(-1, errno, "Failed to mount %d(%s) on \"%s\"", pts_mnt_fd, console->name, lxcpath);
        DEBUG("Mounted \"%s\" onto \"%s\"", console->name, lxcpath);
 
+finish:
        /* bind mount '/dev/<ttydir>/console'  to '/dev/console'  */
        ret = safe_mount(lxcpath, path, "none", MS_BIND, 0, rootfs_path);
        if (ret < 0)
@@ -3316,11 +3343,16 @@ int lxc_setup(struct lxc_handler *handler)
                        return log_error(-1, "Failed to send network device names and ifindices to parent");
        }
 
-       pts_mnt_fd = open_tree(-EBADF, lxc_conf->console.name,
-                              OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC | AT_EMPTY_PATH);
-       if (pts_mnt_fd < 0)
-               SYSTRACE("Failed to create detached mount for container's console \"%s\"",
-                        lxc_conf->console.name);
+       if (wants_console(&lxc_conf->console)) {
+               pts_mnt_fd = open_tree(-EBADF, lxc_conf->console.name,
+                                      OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC | AT_EMPTY_PATH);
+               if (pts_mnt_fd < 0)
+                       SYSTRACE("Failed to create detached mount for container's console \"%s\"",
+                                lxc_conf->console.name);
+               else
+                       TRACE("Created detached mount for container's console \"%s\"",
+                             lxc_conf->console.name);
+       }
 
        if (lxc_conf->autodev > 0) {
                ret = mount_autodev(name, &lxc_conf->rootfs, lxc_conf->autodevtmpfssize, lxcpath);