linux-kernel - Re: [PATCH v3 0/4] Add seccomp notifier ioctl that enables adding fds

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Date:   Wed, 3 Jun 2020 16:56:59 -0700
From:   Sargun Dhillon <sargun@...gun.me>
To:     Kees Cook <keescook@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Tycho Andersen <tycho@...ho.ws>,
        Matt Denton <mpdenton@...gle.com>,
        Jann Horn <jannh@...gle.com>, Chris Palmer <palmer@...gle.com>,
        Aleksa Sarai <cyphar@...har.com>,
        Robert Sesek <rsesek@...gle.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v3 0/4] Add seccomp notifier ioctl that enables adding fds

On Wed, Jun 3, 2020 at 4:42 PM Kees Cook <keescook@...omium.org> wrote:
>
> On Tue, Jun 02, 2020 at 06:10:40PM -0700, Sargun Dhillon wrote:
> > Sargun Dhillon (4):
> >   fs, net: Standardize on file_receive helper to move fds across
> >     processes
> >   pid: Use file_receive helper to copy FDs
>
> The fixes (that should add open-coded cgroups stuff) should be separate
> patches so they can be backported.
Patch 1/4, and 2/4 are separated so they can be backported. Patch 1 should
go into long term, and patch 2 should land in stable.

Do you see anything in 1/4, and 2/4 that shouldn't be there?

>
> The helper doesn't take the __user pointer I thought we'd agreed it
> should to avoid changing any SCM_RIGHTS behaviors?
>
It doesn't change the SCM_RIGHTS behaviour because it continues
to have the logic which allocates the file descriptor outside of the
helper.
1. Allocate FD (this happens in scm.c)
2. Copy FD # to userspace (this happens in scm.c)
3. Receive FD (this happens in the new helper)


> >   seccomp: Introduce addfd ioctl to seccomp user notifier
> >   selftests/seccomp: Test SECCOMP_IOCTL_NOTIF_ADDFD
>
> Otherwise, yeah, this should be good.
>
> --
> Kees Cook