From: Hou Tao <houtao1@huawei.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
Yonghong Song <yhs@fb.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, KP Singh <kpsingh@kernel.org>,
Network Development <netdev@vger.kernel.org>,
bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next 3/4] bpf: Fix net.core.bpf_jit_harden race
Date: Thu, 10 Mar 2022 11:48:45 +0800 [thread overview]
Message-ID: <60bfb6b5-5d2e-cfc2-cc68-2e016ed06918@huawei.com> (raw)
In-Reply-To: <CAADnVQKr12ZRLroU85YC2GvA+WQoFm0On-5yaLE43hy4p8PRJw@mail.gmail.com>
Hi,
On 3/10/2022 11:29 AM, Alexei Starovoitov wrote:
> On Wed, Mar 9, 2022 at 5:01 PM Hou Tao <houtao1@huawei.com> wrote:
>> Hi,
>>
>> On 3/10/2022 7:22 AM, Alexei Starovoitov wrote:
>>> On Wed, Mar 09, 2022 at 08:33:20PM +0800, Hou Tao wrote:
>>>> It is the bpf_jit_harden counterpart to commit 60b58afc96c9 ("bpf: fix
>>>> net.core.bpf_jit_enable race"). bpf_jit_harden will be tested twice
>>>> for each subprog if there are subprogs in bpf program and constant
>>>> blinding may increase the length of program, so when running
>>>> "./test_progs -t subprogs" and toggling bpf_jit_harden between 0 and 2,
>>>> jit_subprogs may fail because constant blinding increases the length
>>>> of subprog instructions during extra passs.
>>>>
>>>> So cache the value of bpf_jit_blinding_enabled() during program
>>>> allocation, and use the cached value during constant blinding, subprog
>>>> JITing and args tracking of tail call.
>>> Looks like this patch alone is enough.
>>> With race fixed. Patches 1 and 2 are no longer necessary, right?
>> Yes and no. With patch 3 applied, the problems described in patch 1 and patch 2
>> are gone, but it may recur due to other issue in JIT. So I post these two patch
>> together and hope these fixes can also be merged.
> What kind of 'issues in JIT'?
> I'd rather fix them than do defensive programming.
Understand. For "issues in JIT" I just mean all kinds of error path handling in
jit, not a real problem.
> patch 2 is a hack that should not happen in a correct JIT.
> .
And "the hack" is partially due to the introduction of an extra pass in JIT. So
I am fine to drop it.
Regards,
Tao
next prev parent reply other threads:[~2022-03-10 3:48 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-09 12:33 [PATCH bpf-next 0/4] fixes for bpf_jit_harden race Hou Tao
2022-03-09 12:33 ` [PATCH bpf-next 1/4] bpf, x86: Fall back to interpreter mode when extra pass fails Hou Tao
2022-03-09 12:33 ` [PATCH bpf-next 2/4] bpf: Introduce bpf_int_jit_abort() Hou Tao
2022-03-11 23:54 ` Daniel Borkmann
2022-03-12 0:20 ` Daniel Borkmann
2022-03-09 12:33 ` [PATCH bpf-next 3/4] bpf: Fix net.core.bpf_jit_harden race Hou Tao
2022-03-09 23:22 ` Alexei Starovoitov
2022-03-10 1:01 ` Hou Tao
2022-03-10 3:29 ` Alexei Starovoitov
2022-03-10 3:48 ` Hou Tao [this message]
2022-03-09 12:33 ` [PATCH bpf-next 4/4] selftests/bpf: Test subprog jit when toggle bpf_jit_harden repeatedly Hou Tao
2022-03-16 22:30 ` [PATCH bpf-next 0/4] fixes for bpf_jit_harden race patchwork-bot+netdevbpf
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