linux-kernel - Re: correctness of BPF stack size checking logic for multi-function programs?

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Message-ID: <CAG48ez2XKDzWjQOD8f17iDGi4JyfZhUhz=uSFKatOZb_7_Xejw@mail.gmail.com>
Date:   Fri, 22 Dec 2017 19:15:38 +0100
From:   Jann Horn <jannh@...gle.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        kernel list <linux-kernel@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: correctness of BPF stack size checking logic for multi-function programs?

On Fri, Dec 22, 2017 at 4:37 AM, Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
> On Fri, Dec 22, 2017 at 02:14:45AM +0100, Jann Horn wrote:
>> Hi!
>>
>> I saw the recently-added support for multiple functions in a single
>> program in BPF. I've stumbled over something that looks like it might
>> be a bug; I haven't verified it yet, but I thought I should give you a
>> heads-up before this lands in a release in case I'm right. If I'm
>> wrong, it might be worth adding a comment to stacksafe() that explains
>> why.
[...]
> but I will rewrite a test case for it unless you beat me to it :)

I just sent a failing test case for the case I'm talking about, subject
"[PATCH] bpf: selftest for late caller stack size increase".