lxc-attach: always allocate current controlling pty

lxc-attach uses lxc_console_create() to allocate a pty on the host.
lxc_console_create() in turn calls lxc_console_peer_default() which either
makes the current controlling pty our controlling pty for the container, or
uses whatever the user gave us (e.g. /dev/tty2 etc.). For lxc-attach we always
want the current controlling pty to be used. This commit ensures that we're in
fact always using the current controlling pty. The commit also fixes a segfault
when the user specified lxc.console.path = none.

Signed-off-by: Christian Brauner <christian.brauner@mailbox.org>

diff --git a/src/lxc/lxc_attach.c b/src/lxc/lxc_attach.c
index 8437965927dff6254a6385a49e2cf6d502fb3531..b6b78244b995eade9f479e0f7fcc3fc452d6c5e4 100644 (file)
--- a/src/lxc/lxc_attach.c
+++ b/src/lxc/lxc_attach.c
@@ -253,10 +253,27 @@ static int get_pty_on_host(struct lxc_container *c, struct wrapargs *wrap, int *
        }
 
        conf = c->lxc_conf;
+       free(conf->console.log_path);
+       conf->console.log_path = NULL;
+
+       /* In the case of lxc-attach our peer pty will always be the current
+        * controlling terminal. We clear whatever was set by the user for
+        * lxc.console.path here and set it to "/dev/tty". Doing this will (a)
+        * prevent segfaults when the container has been setup with
+        * lxc.console = none and (b) provide an easy way to ensure that we
+        * always do the correct thing. strdup() must be used since console.path
+        * is free()ed when we call lxc_container_put(). */
+       free(conf->console.path);
+       conf->console.path = NULL;
+       conf->console.path = strdup("/dev/tty");
+       if (!conf->console.path)
+               return -1;
+
        /* Create pty on the host. */
        if (lxc_console_create(conf) < 0)
                return -1;
        ts = conf->console.tty_state;
+       conf->console.descr = &descr;
 
        /* Shift ttys to container. */
        if (ttys_shift_ids(conf) < 0) {
@@ -375,14 +392,16 @@ int main(int argc, char *argv[])
        attach_options.extra_env_vars = extra_env;
        attach_options.extra_keep_env = extra_keep;
 
-       struct wrapargs wrap = (struct wrapargs){.command = &command,
-               .options = &attach_options};
        if (my_args.argc > 0) {
-               wrap.command->program = my_args.argv[0];
-               wrap.command->argv = (char**)my_args.argv;
+               command.program = my_args.argv[0];
+               command.argv = (char**)my_args.argv;
        }
 
        if (isatty(STDIN_FILENO) || isatty(STDOUT_FILENO) || isatty(STDERR_FILENO)) {
+               struct wrapargs wrap = (struct wrapargs){
+                       .command = &command,
+                       .options = &attach_options
+               };
                if (isatty(STDIN_FILENO))
                        wrap.ptyfd = STDIN_FILENO;
                else if (isatty(STDOUT_FILENO))
@@ -391,7 +410,7 @@ int main(int argc, char *argv[])
                        wrap.ptyfd = STDERR_FILENO;
                ret = get_pty_on_host(c, &wrap, &pid);
        } else {
-               if (my_args.argc > 1)
+               if (command.program)
                        ret = c->attach(c, lxc_attach_run_command, &command, &attach_options, &pid);
                else
                        ret = c->attach(c, lxc_attach_run_shell, NULL, &attach_options, &pid);