Date: Thu, 30 Jul 2015 12:04:35 -0700
From: Josh Triplett <josh@joshtriplett.org>
To: Kees Cook <keescook@chromium.org>
Cc: David Drysdale <drysdale@google.com>, Ingo Molnar <mingo@kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>, Shuah Khan <shuahkh@osg.samsung.com>,
        Jonathan Corbet <corbet@lwn.net>, Eric B Munson <emunson@akamai.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Oleg Nesterov <oleg@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Rusty Russell <rusty@rustcorp.com.au>,
        Peter Zijlstra <peterz@infradead.org>, Vivek Goyal <vgoyal@redhat.com>,
        Alexei Starovoitov <ast@plumgrid.com>,
        David Herrmann <dh.herrmann@gmail.com>,
        "Theodore Ts'o" <tytso@mit.edu>, Milosz Tanski <milosz@adfin.com>,
        Fam Zheng <famz@redhat.com>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCHv2 1/1] Documentation: describe how to add a system call
Message-ID: <20150730190434.GD16452@x>
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On Thu, Jul 30, 2015 at 11:21:54AM -0700, Kees Cook wrote:
> I like this, it's a good description of both options. I'm still biased
> about the approach: I prefer flags, since pointers to user structures
> complicate syscall filtering. ;)

Seems like we should do two things to make that easier:

1) Create a standardized kernel mechanism for parameter-struct handling,
   implementing the recommendations mentioned here.
2) Integrate into that mechanism a way to filter the resulting parameter
   struct with BPF *after* it has been copied to kernel space (and thus
   can no longer be tampered with).

- Josh Triplett
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