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References: <20220108051121.28632-1-yichun@openresty.com>
In-Reply-To: <20220108051121.28632-1-yichun@openresty.com>
From:   Song Liu <song@kernel.org>
Date:   Mon, 10 Jan 2022 14:21:55 -0800
Message-ID: <CAPhsuW5+zCh2ZE6zUq2T=83Z6Ce93z_ojxrqGN9iYN9Qvyq_YQ@mail.gmail.com>
Subject: Re: [PATCH] bpf: core: Fix the call ins's offset s32 -> s16 truncation
To:     "Yichun Zhang (agentzh)" <yichun@openresty.com>
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
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On Fri, Jan 7, 2022 at 9:11 PM Yichun Zhang (agentzh)
<yichun@openresty.com> wrote:
>
> The BPF interpreter always truncates the BPF CALL instruction's 32-bit
> jump offset to 16-bit. Large BPF programs run by the interpreter often
> hit this issue and result in weird behaviors when jumping to the wrong
> destination instructions.
>
> The BPF JIT compiler does not have this bug.
>
> Fixes: 1ea47e01ad6ea ("bpf: add support for bpf_call to interpreter")
> Signed-off-by: Yichun Zhang (agentzh) <yichun@openresty.com>

Acked-by: Song Liu <songliubraving@fb.com>