From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Aleksa Sarai <asarai@suse.de>
Cc: Jiri Slaby <jslaby@suse.com>, Arnd Bergmann <arnd@arndb.de>,
linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org,
linux-mips@linux-mips.org, linux-parisc@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org,
sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org,
linux-arch@vger.kernel.org,
Christian Brauner <christian.brauner@ubuntu.com>,
Valentin Rothberg <vrothberg@suse.com>
Subject: Re: [PATCH v4 2/2] tty: add TIOCGPTPEER ioctl
Date: Fri, 9 Jun 2017 11:26:59 +0200 [thread overview]
Message-ID: <20170609092659.GA26933@kroah.com> (raw)
In-Reply-To: <20170603141515.9529-3-asarai@suse.de>
On Sun, Jun 04, 2017 at 12:15:15AM +1000, Aleksa Sarai wrote:
> 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@ubuntu.com>
> Cc: Valentin Rothberg <vrothberg@suse.com>
> Signed-off-by: Aleksa Sarai <asarai@suse.de>
Is this going to be documented anywhere? Is there a man page update
that also goes along with this? What userspace program wants to use
this?
I'm not objecting to this, I just want to know that people will use
this, and that they can find out information about it if they want to.
thanks,
greg k-h
next prev parent reply other threads:[~2017-06-09 9:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-03 14:15 [PATCH v4 0/2] tty: add TIOCGPTPEER ioctl Aleksa Sarai
2017-06-03 14:15 ` [PATCH v4 1/2] tty: add compat_ioctl callbacks Aleksa Sarai
2017-06-06 12:49 ` Arnd Bergmann
2017-06-03 14:15 ` [PATCH v4 2/2] tty: add TIOCGPTPEER ioctl Aleksa Sarai
2017-06-09 9:26 ` Greg Kroah-Hartman [this message]
2017-06-09 9:50 ` Aleksa Sarai
2017-06-09 10:04 ` Greg Kroah-Hartman
2017-06-09 10:24 ` Aleksa Sarai
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