netdev - Re: [PATCH bpf-next 03/29] bpf: introduce BPF token object

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Message-ID: <20240108-kontinental-drastisch-9fc9a3486d16@brauner>
Date: Mon, 8 Jan 2024 13:01:12 +0100
From: Christian Brauner <brauner@...nel.org>
To: Linus Torvalds <torvalds@...uxfoundation.org>
Cc: Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org, 
	netdev@...r.kernel.org, paul@...l-moore.com, linux-fsdevel@...r.kernel.org, 
	linux-security-module@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH bpf-next 03/29] bpf: introduce BPF token object

> Also, should "current_user_ns() != token->userns" perhaps be an error
> condition, rather than a "fall back to init_ns" condition?

Yes, I've pointed this out before:

"Please enforce that in order to use a token the caller must be in the
same user namespace as the token as well. IOW, we don't want to yet make
it possible to use a token created in an ancestor user namespace to load
or attach bpf programs in a descendant user namespace. Let's be as
restrictive as we can: tokens are only valid within the user namespace
they were created in."

[1] Re: [PATCH v11 bpf-next 03/17] bpf: introduce BPF token object
    https://lore.kernel.org/r/20231130-katzen-anhand-7ad530f187da@brauner

> 
> Again, none of this is a big deal. I do think you're dropping the LSM
> error code on the floor, and are duplicating the "ns_capable()" vs
> "capable()" logic as-is, but none of this is a deal breaker, just more
> of my commentary on the patch and about the logic here.
> 
> And yeah, I don't exactly love how you say "ok, if there's a token and
> it doesn't match, I'll not use it" rather than "if the token namespace
> doesn't match, it's an error", but maybe there's some usability issue
> here?