Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
Date:   Fri, 6 May 2022 08:53:42 +0200 (CEST)
From:   Jiri Kosina <jikos@kernel.org>
To:     Dongliang Mu <dzm91@hust.edu.cn>
cc:     Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        Dongliang Mu <mudongliangabcd@gmail.com>,
        syzkaller <syzkaller@googlegroups.com>,
        linux-input@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] HID: bigben: fix slab-out-of-bounds Write in
 bigben_probe
In-Reply-To: <20220506053740.1113415-1-dzm91@hust.edu.cn>
Message-ID: <nycvar.YFH.7.76.2205060852300.28985@cbobk.fhfr.pm>
References: <20220506053740.1113415-1-dzm91@hust.edu.cn>
User-Agent: Alpine 2.21 (LSU 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Precedence: bulk

On Fri, 6 May 2022, Dongliang Mu wrote:

> From: Dongliang Mu <mudongliangabcd@gmail.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@googlegroups.com>
> Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.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