From: Ilias Apalodimas <ilias.apalodimas@linaro.org>
To: Will Deacon <will@kernel.org>
Cc: bpf@vger.kernel.org, ardb@kernel.org, naresh.kamboju@linaro.org,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
Yauheni Kaliuta <yauheni.kaliuta@redhat.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>,
Zi Shen Lim <zlim.lnx@gmail.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Jesper Dangaard Brouer <hawk@kernel.org>,
netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: bpf: Fix branch offset in JIT
Date: Mon, 14 Sep 2020 19:02:00 +0300 [thread overview]
Message-ID: <20200914160200.GA19026@apalos.home> (raw)
In-Reply-To: <20200914140114.GG24441@willie-the-truck>
Hi Will,
On Mon, Sep 14, 2020 at 03:01:15PM +0100, Will Deacon wrote:
> Hi Ilias,
>
[...]
> > > >
> > > > No Fixes: tag?
> > >
> > > I'll re-spin and apply one
> > >
> > Any suggestion on any Fixes I should apply? The original code was 'correct' and
> > broke only when bounded loops and their self-tests were introduced.
>
> Ouch, that's pretty bad as it means nobody is regression testing BPF on
> arm64 with mainline. Damn.
That might not be entirely true. Since offset is a pointer, there's a chance
(and a pretty high one according to my reproducer) that the offset[-1] value
happens to be 0. In that case the tests will pass fine. I can reproduce the bug
approximately 1 every 6-7 passes here.
I'll send a v2 shortly fixing the tags and adding a few comments on the code,
which will hopefully make future reading easier.
Cheers
/Ilias
next prev parent reply other threads:[~2020-09-14 16:33 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-14 8:36 [PATCH] arm64: bpf: Fix branch offset in JIT Ilias Apalodimas
2020-09-14 12:20 ` Will Deacon
2020-09-14 12:35 ` Ilias Apalodimas
2020-09-14 13:23 ` Ilias Apalodimas
2020-09-14 14:01 ` Will Deacon
2020-09-14 16:02 ` Ilias Apalodimas [this message]
2020-09-14 16:12 ` Jesper Dangaard Brouer
2020-09-14 17:02 ` Ilias Apalodimas
2020-09-14 17:47 ` Xi Wang
2020-09-14 17:55 ` Ilias Apalodimas
2020-09-14 18:08 ` Xi Wang
2020-09-14 18:21 ` Luke Nelson
2020-09-14 18:36 ` Ilias Apalodimas
2020-09-14 18:27 ` Ilias Apalodimas
2020-09-14 18:52 ` Xi Wang
2020-09-14 19:24 ` Ilias Apalodimas
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