terminal: don't use ttyname_r() for native terminal allocation

Since we can call that function from another mount namespace we need to
do this manually.

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

diff --git a/src/lxc/terminal.c b/src/lxc/terminal.c
index 8850a968718f839ea325acb809e5620c8013bb04..2f495bc6248aaecc57c8163f57dc9ec881b7d5b9 100644 (file)
--- a/src/lxc/terminal.c
+++ b/src/lxc/terminal.c
@@ -909,10 +909,12 @@ err:
        return -ENODEV;
 }
 
-static int lxc_terminal_create_native(const char *name, const char *lxcpath, struct lxc_conf *conf,
+static int lxc_terminal_create_native(const char *name, const char *lxcpath,
+                                     struct lxc_conf *conf,
                                      struct lxc_terminal *terminal)
 {
-       __do_close int devpts_fd = -EBADF;
+       __do_close int devpts_fd = -EBADF, fd_pty = -EBADF;
+       int pty_nr = -1;
        int ret;
 
        devpts_fd = lxc_cmd_get_devpts_fd(name, lxcpath);
@@ -949,12 +951,31 @@ static int lxc_terminal_create_native(const char *name, const char *lxcpath, str
                goto err;
        }
 
-       ret = ttyname_r(terminal->pty, terminal->name, sizeof(terminal->name));
+       ret = ioctl(terminal->ptx, TIOCGPTN, &pty_nr);
        if (ret) {
                SYSWARN("Failed to retrieve name of terminal pty");
                goto err;
        }
 
+       fd_pty = open_at(devpts_fd, fdstr(pty_nr), PROTECT_OPATH_FILE,
+                       PROTECT_LOOKUP_ABSOLUTE_XDEV, 0);
+       if (fd_pty < 0) {
+               SYSWARN("Failed to open terminal pty fd by path %d/%d", devpts_fd, pty_nr);
+               goto err;
+       }
+
+       if (!same_file_lax(terminal->pty, fd_pty)) {
+               SYSWARN("Terminal file descriptor changed");
+               goto err;
+       }
+
+       ret = strnprintf(terminal->name, sizeof(terminal->name), "dev/pts/%d",
+                       pty_nr);
+       if (ret < 0) {
+               SYSWARN("Failed to create terminal pty name");
+               goto err;
+       }
+
        ret = lxc_terminal_peer_default(terminal);
        if (ret < 0) {
                SYSWARN("Failed to allocate proxy terminal");