linux-kernel - Re: [PATCH] tty: cleanup prohibition of direct opening for unix98 pty master

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Date:	Wed, 04 Jan 2012 17:26:30 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Greg Kroah-Hartman <gregkh@...e.de>, Alan Cox <alan@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tty: cleanup prohibition of direct opening for unix98
 pty master

Linus Torvalds wrote:
> Looks ok as far as I can tell, and does indeed clean things up. I
> assume somebody tested the case that we used to have issues with?

Yes of course I tested it.

>
>                      Linus
>
> On Tue, Jan 3, 2012 at 12:51 AM, Konstantin Khlebnikov
> <khlebnikov@...nvz.org>  wrote:
>> cleanup hack added in v2.6.27-3203-g15582d3
>>
>> comment from that patch:
>>
>> : pty: If the administrator creates a device for a ptmx slave we should not error
>> :
>> : The open path for ptmx slaves is via the ptmx device. Opening them any
>> : other way is not allowed. Vegard Nossum found that previously this was not
>> : the case and mknod foo c 128 42; cat foo would produce nasty diagnostics
>> :
>> : Signed-off-by: Alan Cox<alan@...hat.com>
>> : Signed-off-by: Linus Torvalds<torvalds@...ux-foundation.org>
>>
>> devpts_get_tty() returns non-null only for inodes on devpts, but there is no
>> inodes for master-devices, /dev/ptmx (/dev/pts/ptmx) is the only way to open them.
>> Thus we can completely forbid lookup for master-devices and eliminate that hack in
>> tty_init_dev() because tty_open() will get EIO from tty_driver_lookup_tty().
>>
>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@...nvz.org>
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