Re: [PATCH v4 2/2] tty: add TIOCGPTPEER ioctl

[Aleksa Sarai]

> > > > When opening the slave end of a PTY, it is not possible for userspace to
> > > > safely ensure that /dev/pts/$num is actually a slave (in cases where the
> > > > mount namespace in which devpts was mounted is controlled by an
> > > > untrusted process). In addition, there are several unresolvable
> > > > race conditions if userspace were to attempt to detect attacks through
> > > > stat(2) and other similar methods [in addition it is not clear how
> > > > userspace could detect attacks involving FUSE].
> > > >
> > > > Resolve this by providing an interface for userpace to safely open the
> > > > "peer" end of a PTY file descriptor by using the dentry cached by
> > > > devpts. Since it is not possible to have an open master PTY without
> > > > having its slave exposed in /dev/pts this interface is safe. This
> > > > interface currently does not provide a way to get the master pty (since
> > > > it is not clear whether such an interface is safe or even useful).
> > > >
> > > > Cc: Christian Brauner <christian.brauner@xxxxxxxxxx>
> > > > Cc: Valentin Rothberg <vrothberg@xxxxxxxx>
> > > > Signed-off-by: Aleksa Sarai <asarai@xxxxxxx>
> > >
> > > Is this going to be documented anywhere?  Is there a man page update
> > > that also goes along with this?
> >
> > I will add one, I didn't know where the man-pages project is hosted / where
> > patches get pushed? What is the ML?
>
>  From the MAINTAINERS file:
>    MAN-PAGES: MANUAL PAGES FOR LINUX -- Sections 2, 3, 4, 5, and 7
>    M:      Michael Kerrisk <mtk.manpages@xxxxxxxxx>
>    W:      http://www.kernel.org/doc/man-pages
>    L:      linux-man@xxxxxxxxxxxxxxx
>    S:      Maintained

Ah, should've looked there first!

Thanks Greg, I'll send it over the weekend.

--
Aleksa Sarai
Software Engineer (Containers)
SUSE Linux GmbH
https://www.cyphar.com/
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