linux-kernel - Re: [PATCH] HID: bigben: fix slab-out-of-bounds Write in bigben

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Message-ID: <nycvar.YFH.7.76.2205060852300.28985@cbobk.fhfr.pm>
Date:   Fri, 6 May 2022 08:53:42 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Dongliang Mu <dzm91@...t.edu.cn>
cc:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Dongliang Mu <mudongliangabcd@...il.com>,
        syzkaller <syzkaller@...glegroups.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: bigben: fix slab-out-of-bounds Write in
 bigben_probe

On Fri, 6 May 2022, Dongliang Mu wrote:

> From: Dongliang Mu <mudongliangabcd@...il.com>
> 
> There is a slab-out-of-bounds Write bug in hid-bigbenff driver.
> The problem is the driver assumes the device must have an input but
> some malicious devices violate this assumption.
> 
> Fix this by checking hid_device's input is non-empty before its usage.
> 
> Reported-by: syzkaller <syzkaller@...glegroups.com>
> Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
> ---
>  drivers/hid/hid-bigbenff.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/hid/hid-bigbenff.c b/drivers/hid/hid-bigbenff.c
> index 74ad8bf98bfd..c14d1774101d 100644
> --- a/drivers/hid/hid-bigbenff.c
> +++ b/drivers/hid/hid-bigbenff.c
> @@ -347,6 +347,11 @@ static int bigben_probe(struct hid_device *hid,
>  	bigben->report = list_entry(report_list->next,
>  		struct hid_report, list);
>  
> +	if (list_empty(&hid->inputs)) {
> +		hid_err(hid, "no inputs found\n");
> +		return -ENODEV;
> +	}
> +

Thanks for the fix. It doesn't seemt o be fully correct though -- as you'd 
be returning -ENODEV here in the situation when hid_hw_start() has already 
happened. So I believe better thing to do here is to do error = -ENODEV; 
goto error_hw_stop;

Could you please fix that up and resend? Thanks,

-- 
Jiri Kosina
SUSE Labs