netdev - Re: More strict error checking in bpf

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Message-ID: <c964892195a6b91d20a67691448567ef528ffa6d.camel@linux.ibm.com>
Date:   Tue, 23 Feb 2021 21:47:32 +0100
From:   Ilya Leoshkevich <iii@...ux.ibm.com>
To:     Ian Denhardt <ian@...hack.net>, ast@...nel.org,
        daniel@...earbox.net, bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: More strict error checking in bpf_asm?

On Tue, 2021-02-23 at 15:26 -0500, Ian Denhardt wrote:
> Hi,
> 
> I'm using the `bpf_asm` tool to do some syscall filtering, and found
> out
> the hard way that its error checking isn't very strict. In particular,
> it issues a warning (not an error) when a jump offset overflows the
> instruction's field. It really seems like this *ought* to be a hard
> error, but I see from the commit message in
> 7e22077d0c73a68ff3fd8b3d2f6564fcbcf8cb23 that this was left as a
> warning
> due to backwards compatibility concerns.

My 2c: when I was writing that commit, I did not have any specific
examples of code that would break in mind - that was pure
speculation/paranoia. So it's OK from my perspective to convert this
fprintf to a hard error.

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