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References: <20220304172852.274126-1-benjamin.tissoires@redhat.com> <20220304172852.274126-16-benjamin.tissoires@redhat.com>
In-Reply-To: <20220304172852.274126-16-benjamin.tissoires@redhat.com>
From:   Song Liu <song@kernel.org>
Date:   Thu, 10 Mar 2022 16:46:18 -0800
Message-ID: <CAPhsuW7Gzr4d=2joK=+BRgyEBQGauo3+-z0=8nZtEKCC22f49A@mail.gmail.com>
Subject: Re: [PATCH bpf-next v2 15/28] bpf/hid: add new BPF type to trigger
 commands from userspace
To:     Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc:     Greg KH <gregkh@linuxfoundation.org>,
        Jiri Kosina <jikos@kernel.org>,
        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>, Shuah Khan <shuah@kernel.org>,
        Dave Marchevsky <davemarchevsky@fb.com>,
        Joe Stringer <joe@cilium.io>,
        Tero Kristo <tero.kristo@linux.intel.com>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:HID CORE LAYER" <linux-input@vger.kernel.org>,
        Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        linux-kselftest@vger.kernel.org
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Precedence: bulk

On Fri, Mar 4, 2022 at 9:33 AM Benjamin Tissoires
<benjamin.tissoires@redhat.com> wrote:
>
> Given that we can not call bpf_hid_raw_request() from within an IRQ,
> userspace needs to have a way to communicate with the device when
> it needs.
>
> Implement a new type that the caller can run at will without being in
> an IRQ context.
>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
>
> ---
[...]

> +       if (user_size_out && data_out) {
> +               user_size_out = min3(user_size_out, (u32)ctx->size, (u32)ctx->allocated_size);
> +
> +               if (copy_to_user(data_out, ctx->data, user_size_out)) {
> +                       ret = -EFAULT;
> +                       goto unlock;
> +               }
> +
> +               if (copy_to_user(&uattr->test.data_size_out,
> +                                &user_size_out,
> +                                sizeof(user_size_out))) {
> +                       ret = -EFAULT;
> +                       goto unlock;
> +               }
> +       }
> +
> +       if (copy_to_user(&uattr->test.retval, &ctx->u.user.retval, sizeof(ctx->u.user.retval))) {
> +               ret = -EFAULT;
> +               goto unlock;

nit: this goto is not really needed.

> +       }
> +
> +unlock:
> +       kfree(ctx);
> +
> +       mutex_unlock(&bpf_hid_mutex);
> +       return ret;
> +}
[...]