TTY: ntty, add one more sanity check

With the previous patch, we fixed another bug where read_buf was freed
while we still was in n_tty_read. We currently check whether read_buf
is NULL at the start of the function. Add one more check after we wake
up from waiting for input.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 0ad32888091c..c3954fbf6ac4 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1815,6 +1815,7 @@ do_it_again:
                         /* FIXME: does n_tty_set_room need locking ? */
                         n_tty_set_room(tty);
                         timeout = schedule_timeout(timeout);
+                        BUG_ON(!tty->read_buf);
                         continue;
                 }
                 __set_current_state(TASK_RUNNING);