From: Martin KaFai Lau <kafai@fb.com>
To: Hou Tao <houtao1@huawei.com>
Cc: <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
KP Singh <kpsingh@kernel.org>
Subject: Re: [PATCH bpf] bpf: handle return value of BPF_PROG_TYPE_STRUCT_OPS prog
Date: Tue, 7 Sep 2021 23:06:11 -0700 [thread overview]
Message-ID: <20210908060611.jylpjegug3gs5gys@kafai-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <20210901085344.3052333-1-houtao1@huawei.com>
On Wed, Sep 01, 2021 at 04:53:44PM +0800, Hou Tao wrote:
> Currently if a function ptr in struct_ops has a return value, its
> caller will get a random return value from it, because the return
> value of related BPF_PROG_TYPE_STRUCT_OPS prog is just dropped.
>
> So adding a new flag BPF_TRAMP_F_RET_FENTRY_RET to tell bpf trampoline
> to save and return the return value of struct_ops prog if ret_size of
> the function ptr is greater than 0. Also restricting the flag to be
> used alone.
Thanks for the report and fix! Sorry for the late reply.
This bug is missed because the tcp-cc func is not always called.
A better test needs to be created to force exercising these funcs
in bpf_test_run(), which can be a follow-up patch in the bpf-next.
Could you help to create this test as a follow up?
The patch lgtm. However, it does not apply cleanly on bpf,
so please rebase and repost. I applied it manually and
tested it by hard coding to call the ->ssthresh() and
observes the return value.
next prev parent reply other threads:[~2021-09-08 6:06 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-01 8:53 [PATCH bpf] bpf: handle return value of BPF_PROG_TYPE_STRUCT_OPS prog Hou Tao
2021-09-07 11:13 ` Hou Tao
2021-09-08 6:06 ` Martin KaFai Lau [this message]
2021-09-08 13:31 ` Hou Tao
2021-09-08 17:19 ` Martin KaFai Lau
2021-09-08 17:27 ` Martin KaFai Lau
2021-09-09 1:45 ` Hou Tao
2021-09-13 20:37 ` Martin KaFai Lau
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