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, 2 insertions, 1 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 75d2a46e106f..3752edc30c36 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1148,7 +1148,8 @@ int tty_check_change(struct tty_struct * tty)
                 return 0;
         if (is_current_pgrp_orphaned())
                 return -EIO;
-        (void) kill_pgrp(task_pgrp(current), SIGTTOU, 1);
+        kill_pgrp(task_pgrp(current), SIGTTOU, 1);
+        set_thread_flag(TIF_SIGPENDING);
         return -ERESTARTSYS;
 }