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Date:   Mon, 12 Sep 2022 12:47:45 +0100
From:   Lee Jones <lee@kernel.org>
To:     linux-kernel@vger.kernel.org, Jiri Kosina <jikos@kernel.org>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        linux-input@vger.kernel.org
Subject: Re: [RESEND] HID: steam: Prevent NULL pointer dereference in
 steam_{recv,send}_report
Message-ID: <Yx8cYZnmnN09lD4A@google.com>
References: <20220803111831.387506-1-lee@kernel.org>
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On Wed, 03 Aug 2022, Lee Jones wrote:

> It is possible for a malicious device to forgo submitting a Feature
> Report.  The HID Steam driver presently makes no prevision for this
> and de-references the 'struct hid_report' pointer obtained from the
> HID devices without first checking its validity.  Let's change that.

This patch has been floating around since the beginning of July.

It fixes a real issue which was found by creating a virtual
(software based) malicious device and registering it as a HID device.

There is nothing preventing a real attacker from creating a H/W
version of the device in order to instigate an out-of-bounds read,
potentially leading to a data leak.

Would someone be kind enough to review please?

> Cc: Jiri Kosina <jikos@kernel.org>
> Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> Cc: linux-input@vger.kernel.org
> Fixes: c164d6abf3841 ("HID: add driver for Valve Steam Controller")
> Signed-off-by: Lee Jones <lee@kernel.org>
> ---
>  drivers/hid/hid-steam.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/hid/hid-steam.c b/drivers/hid/hid-steam.c
> index a3b151b29bd71..fc616db4231bb 100644
> --- a/drivers/hid/hid-steam.c
> +++ b/drivers/hid/hid-steam.c
> @@ -134,6 +134,11 @@ static int steam_recv_report(struct steam_device *steam,
>  	int ret;
>  
>  	r = steam->hdev->report_enum[HID_FEATURE_REPORT].report_id_hash[0];
> +	if (!r) {
> +		hid_err(steam->hdev, "No HID_FEATURE_REPORT submitted -  nothing to read\n");
> +		return -EINVAL;
> +	}
> +
>  	if (hid_report_len(r) < 64)
>  		return -EINVAL;
>  
> @@ -165,6 +170,11 @@ static int steam_send_report(struct steam_device *steam,
>  	int ret;
>  
>  	r = steam->hdev->report_enum[HID_FEATURE_REPORT].report_id_hash[0];
> +	if (!r) {
> +		hid_err(steam->hdev, "No HID_FEATURE_REPORT submitted -  nothing to read\n");
> +		return -EINVAL;
> +	}
> +
>  	if (hid_report_len(r) < 64)
>  		return -EINVAL;
>  

-- 
Lee Jones [李琼斯]