2008-08-08 10:58:17

by Kanru Chen

Subject: [PATCH] tty_io: fix tiocswinsz, tiocgwinsz races.

real_tty may receive SIGWINCH before the new winsize is setted.

Signed-off-by: Kanru Chen <[email protected]>
---
drivers/char/tty_io.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index e1b46bc..63703ea 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -2523,6 +2523,8 @@ static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
return -EFAULT;

mutex_lock(&tty->termios_mutex);
+ if (real_tty != tty)
+ mutex_lock(&real_tty->termios_mutex);
if (!memcmp(&tmp_ws, &tty->winsize, sizeof(*arg)))
goto done;

@@ -2553,6 +2555,8 @@ static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
tty->winsize = tmp_ws;
real_tty->winsize = tmp_ws;
done:
+ if (real_tty != tty)
+ mutex_unlock(&real_tty->termios_mutex);
mutex_unlock(&tty->termios_mutex);
return 0;
}
--
1.5.6.3

2008-08-08 12:08:29

by Alan

Subject: Re: [PATCH] tty_io: fix tiocswinsz, tiocgwinsz races.

On Fri, 8 Aug 2008 18:36:18 +0800
Kanru Chen <[email protected]> wrote:

> real_tty may receive SIGWINCH before the new winsize is setted.

It needs rather more than that - for the moment I've gone back to the old
races because there is an awkward deadlock case to deal with. I've pushed
some changes to the -next tree to rework all this locking.

I had however missed the tty/real_tty case so something like your changes
might still be relevant. I'll take a look.