linux-kernel - Re: [PATCH] net: filter: fix upper BPF instruction limit

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Message-ID: <CAMEtUuzbPExM5dT+xDqbHtV5LZ3+E2Q0eq4xdmKWzLOZbTmuUQ@mail.gmail.com>
Date:	Wed, 18 Jun 2014 15:48:05 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Daniel Borkmann <dborkman@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Chema Gonzalez <chema@...gle.com>,
	Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: filter: fix upper BPF instruction limit

On Wed, Jun 18, 2014 at 3:34 PM, Kees Cook <keescook@...omium.org> wrote:
> The original checks (via sk_chk_filter) for instruction count uses ">",
> not ">=", so changing this in sk_convert_filter has the potential to break
> existing seccomp filters that used exactly BPF_MAXINSNS many instructions.
>
> Fixes: bd4cf0ed331a ("net: filter: rework/optimize internal BPF interpreter's instruction set")
> Signed-off-by: Kees Cook <keescook@...omium.org>
> Cc: stable@...r.kernel.org # v3.15+

Acked-by: Alexei Starovoitov <ast@...mgrid.com>

I wonder how did you catch this? :)
Just code inspection or seccomp actually generating such programs?

Thanks!
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