From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Jiong Wang <jiong.wang@netronome.com>
Cc: ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org,
oss-drivers@netronome.com
Subject: Re: [PATCH bpf-next] bpf: correct slot_type marking logic to allow more stack slot sharing
Date: Tue, 18 Dec 2018 14:48:15 -0800 [thread overview]
Message-ID: <20181218224814.vjvxsob25xb5ko3f@ast-mbp> (raw)
In-Reply-To: <1544862880-23291-1-git-send-email-jiong.wang@netronome.com>
On Sat, Dec 15, 2018 at 03:34:40AM -0500, Jiong Wang wrote:
> Verifier is supposed to support sharing stack slot allocated to ptr with
> SCALAR_VALUE for privileged program. However this doesn't happen for some
> cases.
>
> The reason is verifier is not clearing slot_type STACK_SPILL for all bytes,
> it only clears part of them, while verifier is using:
>
> slot_type[0] == STACK_SPILL
>
> as a convention to check one slot is ptr type.
>
> So, the consequence of partial clearing slot_type is verifier could treat a
> partially overridden ptr slot, which should now be a SCALAR_VALUE slot,
> still as ptr slot, and rejects some valid programs.
>
> Before this patch, test_xdp_noinline.o under bpf selftests, bpf_lxc.o and
> bpf_netdev.o under Cilium bpf repo, when built with -mattr=+alu32 are
> rejected due to this issue. After this patch, they all accepted.
>
> There is no processed insn number change before and after this patch on
> Cilium bpf programs.
>
> Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Applied, Thanks
prev parent reply other threads:[~2018-12-18 22:48 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-15 8:34 [PATCH bpf-next] bpf: correct slot_type marking logic to allow more stack slot sharing Jiong Wang
2018-12-18 22:28 ` Daniel Borkmann
2018-12-18 22:48 ` Alexei Starovoitov [this message]
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