From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Jiong Wang <jiong.wang@netronome.com>
Cc: bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [RFC PATCH] bpf: handle 32-bit zext during constant blinding
Date: Wed, 21 Aug 2019 14:00:44 +0530 [thread overview]
Message-ID: <1566376025.68ldwx3wc7.naveen@linux.ibm.com> (raw)
In-Reply-To: <20190813171018.28221-1-naveen.n.rao@linux.vnet.ibm.com>
Naveen N. Rao wrote:
> Since BPF constant blinding is performed after the verifier pass, there
> are certain ALU32 instructions inserted which don't have a corresponding
> zext instruction inserted after. This is causing a kernel oops on
> powerpc and can be reproduced by running 'test_cgroup_storage' with
> bpf_jit_harden=2.
>
> Fix this by emitting BPF_ZEXT during constant blinding if
> prog->aux->verifier_zext is set.
>
> Fixes: a4b1d3c1ddf6cb ("bpf: verifier: insert zero extension according to analysis result")
> Reported-by: Michael Ellerman <mpe@ellerman.id.au>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> ---
> This approach (the location where zext is being introduced below, in
> particular) works for powerpc, but I am not entirely sure if this is
> sufficient for other architectures as well. This is broken on v5.3-rc4.
Alexie, Daniel, Jiong,
Any feedback on this?
- Naveen
next prev parent reply other threads:[~2019-08-21 8:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-13 17:10 [RFC PATCH] bpf: handle 32-bit zext during constant blinding Naveen N. Rao
2019-08-21 8:30 ` Naveen N. Rao [this message]
2019-08-21 9:05 ` Jiong Wang
2019-08-21 10:25 ` Regression fix for bpf in v5.3 (was Re: [RFC PATCH] bpf: handle 32-bit zext during constant blinding) Michael Ellerman
2019-08-21 10:55 ` Jiong Wang
2019-08-21 19:12 ` Naveen N. Rao
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