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Subject: Re: [PATCH v3] HID: betop: fix slab-out-of-bounds Write in
 betop_probe
To:     "F.A.Sulaiman" <asha.16@itfac.mrt.ac.lk>, jikos@kernel.org,
        benjamin.tissoires@redhat.com
Cc:     linux-input@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210816201544.26405-1-asha.16@itfac.mrt.ac.lk>
 <20210824150730.9118-1-asha.16@itfac.mrt.ac.lk>
From:   Pavel Skripkin <paskripkin@gmail.com>
Message-ID: <e8e7f55a-75dd-6631-13e0-eab350712a38@gmail.com>
Date:   Tue, 24 Aug 2021 18:12:46 +0300
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On 8/24/21 6:07 PM, F.A.Sulaiman wrote:
> Syzbot reported slab-out-of-bounds Write bug in hid-betopff driver.
> The problem is the driver assumes the device must have an input report but
> some malicious devices violate this assumption.
> 
> So this patch checks hid_device's input is non empty before it's been used.
> 
> Reported-by: syzbot+07efed3bc5a1407bd742@syzkaller.appspotmail.com
> Signed-off-by: F.A. SULAIMAN <asha.16@itfac.mrt.ac.lk>


Reviewed-by: Pavel Skripkin <paskripkin@gmail.com>


> ---
>   drivers/hid/hid-betopff.c | 13 ++++++++++---
>   1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hid/hid-betopff.c b/drivers/hid/hid-betopff.c
> index 0790fbd3fc9a..467d789f9bc2 100644
> --- a/drivers/hid/hid-betopff.c
> +++ b/drivers/hid/hid-betopff.c
> @@ -56,15 +56,22 @@ static int betopff_init(struct hid_device *hid)
>   {
>   	struct betopff_device *betopff;
>   	struct hid_report *report;
> -	struct hid_input *hidinput =
> -			list_first_entry(&hid->inputs, struct hid_input, list);
> +	struct hid_input *hidinput;
>   	struct list_head *report_list =
>   			&hid->report_enum[HID_OUTPUT_REPORT].report_list;
> -	struct input_dev *dev = hidinput->input;
> +	struct input_dev *dev;
>   	int field_count = 0;
>   	int error;
>   	int i, j;
>   
> +	if (list_empty(&hid->inputs)) {
> +		hid_err(hid, "no inputs found\n");
> +		return -ENODEV;
> +	}
> +
> +	hidinput = list_first_entry(&hid->inputs, struct hid_input, list);
> +	dev = hidinput->input;
> +
>   	if (list_empty(report_list)) {
>   		hid_err(hid, "no output reports found\n");
>   		return -ENODEV;
>