linux-kernel - Re: [PATCH] bpf: handle 32-bit zext during constant blinding

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Message-ID: <776c3058-ebd4-f30d-7392-03a4a94c2483@iogearbox.net>
Date:   Mon, 26 Aug 2019 23:34:13 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Jiong Wang <jiong.wang@...ronome.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>, bpf@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bpf: handle 32-bit zext during constant blinding

On 8/21/19 9:23 PM, Naveen N. Rao wrote:
> Since BPF constant blinding is performed after the verifier pass, the
> ALU32 instructions inserted for doubleword immediate loads don't have a
> corresponding zext instruction. 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@...erman.id.au>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>

LGTM, applied to bpf, thanks!