netdev - Re: [offlist] Re: Crash in netlink/sk_filter_trim

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Date:   Fri, 17 Aug 2018 22:12:28 +0100
From:   Peter Robinson <pbrobinson@...il.com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Marc Haber <mh+netdev@...schlus.de>,
        linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
        labbott@...hat.com, Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [offlist] Re: Crash in netlink/sk_filter_trim_cap on ARMv7 on 4.18rc1

On Fri, Aug 17, 2018 at 5:17 PM, Russell King - ARM Linux
<linux@...linux.org.uk> wrote:
> On Fri, Aug 17, 2018 at 02:40:19PM +0200, Daniel Borkmann wrote:
>> I'd have one potential bug suspicion, for the 4.18 one you were trying,
>> could you run with the below patch to see whether it would help?
>
> I think this is almost certainly the problem - looking at the history,
> it seems that the "-4" was assumed to be part of the scratch stuff in
> commit 38ca93060163 ("bpf, arm32: save 4 bytes of unneeded stack space")
> but it isn't - it's because "off" of zero refers to the top word in the
> stack (iow at STACK_SIZE-4).

I can confirm that patch fixes the problem I was seeing.

Peter