Commit 70362511 authored Dec 17, 2009 by Greg Kroah-Hartman

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@xmission.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tavis Ormandy <taviso@google.com>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Julien Tinnes <jln@google.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

parent 18c576f9

drivers/char/tty_io.c

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -1951,8 +1951,8 @@ static int tty_fasync(int fd, struct file *filp, int on)
	pid = task_pid(current);		pid = task_pid(current);
	type = PIDTYPE_PID;		type = PIDTYPE_PID;
	}		}
	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
	retval = __f_setown(filp, pid, type, 0);		retval = __f_setown(filp, pid, type, 0);
			spin_unlock_irqrestore(&tty->ctrl_lock, flags);
	if (retval)		if (retval)
	goto out;		goto out;
	} else {		} else {