netdev - Re: [PATCHv2] net: bpf: reject invalid shifts

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Message-ID: <1452658064.1223.58.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 12 Jan 2016 20:07:44 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	alexei.starovoitov@...il.com, daniel@...earbox.net, rabin@....in,
	netdev@...r.kernel.org, ast@...nel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCHv2] net: bpf: reject invalid shifts

On Tue, 2016-01-12 at 21:43 -0500, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Tue, 12 Jan 2016 18:11:38 -0800
> 
> > As I said, it is possible some guys never noticed their BPF program
> > were 'broken' because this invalid shift was hidden in a dead code
> > part.
> 
> We should not hide bugs and unintended uses of operations with
> undefined behavior.

   JUMP 2:
   SHR  45
2: RET  10


was a valid program.

But a dumb loader decided to know better.