Re: [PATCH] tty: cleanup prohibition of direct opening for unix98pty master

[Konstantin Khlebnikov]

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@xxxxxxxxxx>  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@xxxxxxxxxx>
> > : Signed-off-by: Linus Torvalds<torvalds@xxxxxxxxxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
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