linux-kernel - [PATCH 8/8] tty: fix race in tty

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Date:	Wed, 20 Jan 2010 15:50:03 -0800
From:	Greg Kroah-Hartman <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...e.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Al Viro <viro@...IV.linux.org.uk>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Tavis Ormandy <taviso@...gle.com>,
	Jeff Dike <jdike@...toit.com>, Julien Tinnes <jln@...gle.com>,
	Matt Mackall <mpm@...enic.com>, stable <stable@...nel.org>
Subject: [PATCH 8/8] tty: fix race in tty_fasync

We need to keep the lock held over the call to __f_setown() to
prevent a PID race.

Thanks to Al Viro for pointing out the problem, and to Travis for
making us look here in the first place.

Cc: Eric W. Biederman <ebiederm@...ssion.com>
Cc: Al Viro <viro@...IV.linux.org.uk>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Tavis Ormandy <taviso@...gle.com>
Cc: Jeff Dike <jdike@...toit.com>
Cc: Julien Tinnes <jln@...gle.com>
Cc: Matt Mackall <mpm@...enic.com>
Cc: stable <stable@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 drivers/char/tty_io.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index f15df40..c6f3b48 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1951,8 +1951,8 @@ static int tty_fasync(int fd, struct file *filp, int on)
 			pid = task_pid(current);
 			type = PIDTYPE_PID;
 		}
-		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 		retval = __f_setown(filp, pid, type, 0);
+		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 		if (retval)
 			goto out;
 	} else {
-- 
1.6.5.7

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