Re: [Qemu-devel] pty/tty functions for BSD too

["Blue Swirl" <blauwirbel@gmail.com>]

On 8/18/08, Daniel P. Berrange <berrange@redhat.com> wrote:
> On Mon, Aug 18, 2008 at 07:16:36PM +0300, Blue Swirl wrote:
>  > On 8/18/08, Samuel Thibault <samuel.thibault@ens-lyon.org> wrote:
>  > > Anthony Liguori, le Mon 18 Aug 2008 09:06:41 -0500, a écrit :
>  > >
>  > > > Samuel Thibault wrote:
>  > >  > >In Xen, pty/tty functions are enabled for BSD too, shouldn't we enable
>  > >  > >them in upstream qemu too, as patched below?
>  > >  > >
>  > >  >
>  > >  > And you're sure that these functions compile/work on NetBSD/OpenBSD?
>  > >
>  > >
>  > > The defines are explicit in Xen, so I guess somebody tested it.  I
>  > >  haven't myself.  I wonder why there is no FreeBSD however.
>  >
>  > The patch does not work on OpenBSD, because while openpty() is
>  > available, ptsname() isn't.
>  >
>  > I tested the attached version on OpenBSD and Linux, pty name is
>  > printed correctly.
>
>
> Passing a non-NULL value to openpty()'s name parameter is not safe
>
>  [quote openpty(1)]
>  BUGS
>        Nobody knows how much space should be reserved for name.  So, call-
>        ing openpty() or forkpty() with non-NULL name may not be secure.
>  [/quote]

Maybe in theory, but in practice the name will be
/dev/pty[0-9a-z][a-z] or /dev/pts/[0-9]* or something similar. Even if
they are not, PATH_MAX should be enough.

>  If BSD has no other way to determine the PTY name, then at least it
>  should be conditionalized so that systems with ptsname() use it, only
>  falling back to using the 'name' arg to openpty() for OS lacking ptsname

I'm not convinced (yet?) this will be worth it.