linux-kernel - Re: [PATCH] bpf: core: Fix the call ins's offset s32 -> s16 truncation

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Message-ID: <CAPhsuW5+zCh2ZE6zUq2T=83Z6Ce93z_ojxrqGN9iYN9Qvyq_YQ@mail.gmail.com>
Date:   Mon, 10 Jan 2022 14:21:55 -0800
From:   Song Liu <song@...nel.org>
To:     "Yichun Zhang (agentzh)" <yichun@...nresty.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] bpf: core: Fix the call ins's offset s32 -> s16 truncation

On Fri, Jan 7, 2022 at 9:11 PM Yichun Zhang (agentzh)
<yichun@...nresty.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@...nresty.com>

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