linux-kernel - Re: [PATCH] security: selinux: allow per-file labeling for bpffs

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Message-ID: <CAKLm694DMH0JCpHuT4HgMd4yCNJZPFMpex8iEiRF9kRjPb0d6g@mail.gmail.com>
Date:   Thu, 6 Feb 2020 09:41:41 -0800
From:   Steven Moreland <smoreland@...gle.com>
To:     Stephen Smalley <sds@...ho.nsa.gov>
Cc:     paul@...l-moore.com, eparis@...isplace.org, keescook@...omium.org,
        anton@...msg.org, Colin Cross <ccross@...roid.com>,
        tony.luck@...el.com, selinux@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        "Connor O'Brien" <connoro@...gle.com>
Subject: Re: [PATCH] security: selinux: allow per-file labeling for bpffs

On Thu, Feb 6, 2020 at 9:35 AM Stephen Smalley <sds@...ho.nsa.gov> wrote:
>
> On 2/6/20 12:21 PM, Stephen Smalley wrote:
> > On 2/6/20 11:55 AM, Steven Moreland wrote:
> >> From: Connor O'Brien <connoro@...gle.com>
> >>
> >> Add support for genfscon per-file labeling of bpffs files. This allows
> >> for separate permissions for different pinned bpf objects, which may
> >> be completely unrelated to each other.
> >
> > Do you want bpf fs to also support userspace labeling of files via
> > setxattr()?  If so, you'll want to also add it to
> > selinux_is_genfs_special_handling() as well.
> >

Android doesn't currently have this use case.

> > The only caveat I would note here is that it appears that bpf fs
> > supports rename, link, unlink, rmdir etc by userspace, which means that
> > name-based labeling via genfscon isn't necessarily safe/stable.  See
> > https://github.com/SELinuxProject/selinux-kernel/issues/2
> >

Android restricts ownership of these files to a single process (bpfloader) and
so this isn't a concern in our architecture. Is it a concern in general?

> >> Change-Id: I03ae28d3afea70acd6dc53ebf810b34b357b6eb5
> >
> > Drop Change-Ids from patches submitted upstream please since they aren't
> > meaningful outside of Android.
> >

Yeah, will resubmit, thanks.

> >> Signed-off-by: Connor O'Brien <connoro@...gle.com>
> >> Signed-off-by: Steven Moreland <smoreland@...gle.com>
> >> ---
> >>   security/selinux/hooks.c | 1 +
> >>   1 file changed, 1 insertion(+)
> >>
> >> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> >> index de4887742d7c..4f9396e6ce8c 100644
> >> --- a/security/selinux/hooks.c
> >> +++ b/security/selinux/hooks.c
> >> @@ -872,6 +872,7 @@ static int selinux_set_mnt_opts(struct super_block
> >> *sb,
> >>           !strcmp(sb->s_type->name, "sysfs") ||
> >>           !strcmp(sb->s_type->name, "pstore") ||
> >>           !strcmp(sb->s_type->name, "binder") ||
> >> +        !strcmp(sb->s_type->name, "bpf") ||
> >>           !strcmp(sb->s_type->name, "cgroup") ||
> >>           !strcmp(sb->s_type->name, "cgroup2"))
> >>           sbsec->flags |= SE_SBGENFS;
> >>
>
> Also, your patch appears to be based on an old kernel and won't apply
> upstream; see
> https://github.com/SELinuxProject/selinux-kernel/blob/master/README.md
>

Will resubmit, thanks.