linux-kernel - Re: [PATCH 18/27] bpf: Restrict kernel image access functions when the kernel is locked down

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Message-ID: <13472.1510247704@warthog.procyon.org.uk>
Date:   Thu, 09 Nov 2017 17:15:04 +0000
From:   David Howells <dhowells@...hat.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     dhowells@...hat.com, jlee@...e.com,
        linux-security-module@...r.kernel.org, gnomes@...rguk.ukuu.org.uk,
        linux-efi@...r.kernel.org, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, jforbes@...hat.com,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 18/27] bpf: Restrict kernel image access functions when the kernel is locked down

Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:

> > TBH, I've no idea how bpf does anything, so I can't say whether this is
> > better, overkill or insufficient.
> 
> ok. To make it clear:
> Nacked-by: Alexei Starovoitov <ast@...nel.org>
> For the current patch.
> Unnecessary checks for no good reason in performance critical
> functions are not acceptable.

They aren't unnecessary checks.

Can you please suggest if there's some way more suitable than just killing bpf
entirely?  I don't know the code, and I presume you do.

David