netdev - Re: [PATCH bpf-next v2] Update perf ring buffer to prevent corruption

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Message-ID: <20201109112908.GG2594@hirez.programming.kicks-ass.net>
Date:   Mon, 9 Nov 2020 12:29:08 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Kevin Sheldrake <Kevin.Sheldrake@...rosoft.com>,
        Ingo Molnar <mingo@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Network Development <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        KP Singh <kpsingh@...gle.com>
Subject: Re: [PATCH bpf-next v2] Update perf ring buffer to prevent corruption

On Thu, Nov 05, 2020 at 08:19:47PM -0800, Alexei Starovoitov wrote:
> On Thu, Nov 5, 2020 at 7:18 AM Kevin Sheldrake
> <Kevin.Sheldrake@...rosoft.com> wrote:
> >
> > Resent due to some failure at my end.  Apologies if it arrives twice.
> >
> > From 63e34d4106b4dd767f9bfce951f8a35f14b52072 Mon Sep 17 00:00:00 2001
> > From: Kevin Sheldrake <kevin.sheldrake@...rosoft.com>
> > Date: Thu, 5 Nov 2020 12:18:53 +0000
> > Subject: [PATCH] Update perf ring buffer to prevent corruption from
> >  bpf_perf_output_event()
> >
> > The bpf_perf_output_event() helper takes a sample size parameter of u64, but
> > the underlying perf ring buffer uses a u16 internally. This 64KB maximum size
> > has to also accommodate a variable sized header. Failure to observe this
> > restriction can result in corruption of the perf ring buffer as samples
> > overlap.
> >
> > Track the sample size and return -E2BIG if too big to fit into the u16
> > size parameter.
> >
> > Signed-off-by: Kevin Sheldrake <kevin.sheldrake@...rosoft.com>
> 
> The fix makes sense to me.
> Peter, Ingo,
> should I take it through the bpf tree or you want to route via tip?

What are you doing to trigger this? The Changelog is devoid of much
useful information?