Re: [PATCH v2 06/19] tty: Fix unsafe ldisc reference via ioctl(TIOCGETD)

From: Peter Hurley
Date: Sun Jan 10 2016 - 00:26:09 EST

On 01/09/2016 08:40 PM, Peter Hurley wrote:
> ioctl(TIOCGETD) retrieves the line discipline id directly from the
> ldisc because the line discipline id (c_line) in termios is untrustworthy;
> userspace may have set termios via ioctl(TCSETS*) without actually
> changing the line discipline via ioctl(TIOCSETD).
> However, directly accessing the current ldisc via tty->ldisc is
> unsafe; the ldisc ptr dereferenced may be stale if the line discipline
> is changing via ioctl(TIOCSETD) or hangup.
> Wait for the line discipline reference (just like read() or write())
> to retrieve the "current" line discipline id.

Hi Greg,

I forgot to re-mark this patch for stable.

Peter Hurley