netdev - Re: [PATCH bpf] bpf: arsh is not supported in 32 bit alu thus reject it

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Message-ID: <20180110225704.qquylvq7igzqhxb4@ast-mbp>
Date:   Wed, 10 Jan 2018 14:57:06 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     ast@...com, netdev@...r.kernel.org
Subject: Re: [PATCH bpf] bpf: arsh is not supported in 32 bit alu thus reject
 it

On Wed, Jan 10, 2018 at 08:04:37PM +0100, Daniel Borkmann wrote:
> The following snippet was throwing an 'unknown opcode cc' warning
> in BPF interpreter:
> 
>   0: (18) r0 = 0x0
>   2: (7b) *(u64 *)(r10 -16) = r0
>   3: (cc) (u32) r0 s>>= (u32) r0
>   4: (95) exit
> 
> Although a number of JITs do support BPF_ALU | BPF_ARSH | BPF_{K,X}
> generation, not all of them do and interpreter does neither. We can
> leave existing ones and implement it later in bpf-next for the
> remaining ones, but reject this properly in verifier for the time
> being.
> 
> Fixes: 17a5267067f3 ("bpf: verifier (add verifier core)")
> Reported-by: syzbot+93c4904c5c70348a6890@...kaller.appspotmail.com
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>

ouch. it's been there forever.
Applied, Thank you Daniel.