tty: fix leakage of -ERESTARTSYS to userland

Spotted by Satoru Takeuchi.

kill_pgrp(task_pgrp(current)) sends the signal to the current's thread
group, but can choose any sub-thread as a target for signal_wake_up().
This means that job_control() and tty_check_change() may return
-ERESTARTSYS without signal_pending().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index b3d4ccc33a47..154f42203b05 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -1191,6 +1191,7 @@ static int job_control(struct tty_struct *tty, struct file *file)
                             is_current_pgrp_orphaned())
                                 return -EIO;
                         kill_pgrp(task_pgrp(current), SIGTTIN, 1);
+                        set_thread_flag(TIF_SIGPENDING);
                         return -ERESTARTSYS;
                 }
         }