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

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Message-ID: <5691EB16.1020607@hurleysoftware.com>
Date:	Sat, 9 Jan 2016 21:24:38 -0800
From:	Peter Hurley <peter@...leysoftware.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Jiri Slaby <jslaby@...e.cz>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 06/19] tty: Fix unsafe ldisc reference via
 ioctl(TIOCGETD)

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.

Regards,
Peter Hurley