linux-kernel - Re: [PATCH bpf-next v6 02/23] bpf/verifier: allow kfunc to read user provided context

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Date:   Fri, 15 Jul 2022 16:56:54 -0700
From:   Yonghong Song <yhs@...com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Jiri Kosina <jikos@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Shuah Khan <shuah@...nel.org>,
        Dave Marchevsky <davemarchevsky@...com>,
        Joe Stringer <joe@...ium.io>, Jonathan Corbet <corbet@....net>
Cc:     Tero Kristo <tero.kristo@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH bpf-next v6 02/23] bpf/verifier: allow kfunc to read user
 provided context



On 7/12/22 7:58 AM, Benjamin Tissoires wrote:
> When a kfunc was trying to access data from context in a syscall eBPF
> program, the verifier was rejecting the call.
> This is because the syscall context is not known at compile time, and
> so we need to check this when actually accessing it.
> 
> Check for the valid memory access and allow such situation to happen.
> 
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>

Acked-by: Yonghong Song <yhs@...com>