linux-kernel - Re: [PATCH 3/4] TTY: pty, release tty in all ptmx

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Date:	Wed, 12 Oct 2011 15:23:05 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	gregkh@...e.de, linux-kernel@...r.kernel.org, jirislaby@...il.com,
	stable@...nel.org, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH 3/4] TTY: pty, release tty in all ptmx_open fail paths

On Wednesday 12 October 2011, Jiri Slaby wrote:
> Mistakenly, commit 64ba3dc3143d (tty: never hold BTM while getting
> tty_mutex) switched one fail path in ptmx_open to not free the newly
> allocated tty.
> 
> Fix that by jumping to the appropriate place. And rename the labels so
> that it's clear what is going on there.
> 
> Introduced-in: v2.6.36-rc2
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Cc: stable@...nel.org
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
> Cc: Greg Kroah-Hartman <gregkh@...e.de>

Ok, I have checked that this patch returns the code into the state
before my broken patch, that looks good.

I think I made the same mistake trying to understand your patch
that I made originally when I introduced the bug, which was to
confuse the lifetime of the pty master with the lifetime of the
slave device, so I thought that tty_release should not be called
if we never called ptm_driver->ops->open(), but that's actually
a different device.

	Arnd
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