[PATCH 1/1] tty: set_termios/set_termiox should not return -EINTR

[Oleg Nesterov <oleg@redhat.com>]

See https://bugzilla.redhat.com/show_bug.cgi?id=904907
read command causes bash to abort with double free or corruption (out).

A simple test-case from Roman:

	// Compile the reproducer and send sigchld ti that process.
	// EINTR occurs even if SA_RESTART flag is set.

	void handler(int sig)
	{
	}

	main()
	{
	  struct sigaction act;
	  act.sa_handler = handler;
	  act.sa_flags = SA_RESTART;
	  sigaction (SIGCHLD, &act, 0);
	  struct termio ttp;
	  ioctl(0, TCGETA, &ttp);
	  while(1)
	  {
	    if (ioctl(0, TCSETAW, ttp) < 0)
	      {
		if (errno == EINTR)
		{
		  fprintf(stderr, "BUG!"); return(1);
		}
	      }
	  }
	}

Change set_termios/set_termiox to return -ERESTARTSYS to fix this
particular problem.

I didn't dare to change other EINTR's in drivers/tty/, but they look
equally wrong.

Reported-by: Roman Rakus <rrakus@redhat.com>
Reported-by: Lingzhu Xiang <lxiang@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: stable@kernel.org
---

--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -617,7 +617,7 @@ static int set_termios(struct tty_struct *tty, void __user *arg, int opt)
 	if (opt & TERMIOS_WAIT) {
 		tty_wait_until_sent(tty, 0);
 		if (signal_pending(current))
-			return -EINTR;
+			return -ERESTARTSYS;
 	}
 
 	tty_set_termios(tty, &tmp_termios);
@@ -684,7 +684,7 @@ static int set_termiox(struct tty_struct *tty, void __user *arg, int opt)
 	if (opt & TERMIOS_WAIT) {
 		tty_wait_until_sent(tty, 0);
 		if (signal_pending(current))
-			return -EINTR;
+			return -ERESTARTSYS;
 	}
 
 	mutex_lock(&tty->termios_mutex);