Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <80f92044-6f3d-cdd8-a7d4-8793927a648b@linux.intel.com>
Date:   Thu, 23 Mar 2023 14:51:38 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Firefox/102.0 Thunderbird/102.7.1
Content-Language: en-US
To:     Jia-Ju Bai <baijiaju@buaa.edu.cn>, mathias.nyman@intel.com,
        gregkh@linuxfoundation.org, p.zabel@pengutronix.de
Cc:     linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20230323081329.366459-1-baijiaju@buaa.edu.cn>
From:   Mathias Nyman <mathias.nyman@linux.intel.com>
Subject: Re: [PATCH] usb: host: xhci: Add a NULL check of hcd in
 xhci_plat_remove()
In-Reply-To: <20230323081329.366459-1-baijiaju@buaa.edu.cn>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 23.3.2023 10.13, Jia-Ju Bai wrote:
> In a previous commit d7de14d74d65 ("usb: xhci_plat_remove: avoid NULL
> dereference"), hcd can be NULL in usb_remove_hcd(), and thus it should
> be checked before being used.

hcd shouldn't be null in usb_remove_hcd()
That was a bug which was properly fixed shortly after in:

4a593a62a9e3 xhci: Fix null pointer dereference in remove if xHC has only one roothub

I guess commit d7de14d74d65 ("usb: xhci_plat_remove: avoid NULL dereference") Isn't really
needed either anymore, but no harm in keeping it.

> 
> However, in the call stack of this commit, hci is also used to get xhci:
> > xhci_plat_remove()
>    xhci = hcd_to_xhci(hcd)
>      usb_hcd_is_primary_hcd(hcd)
>        if (!hcd->primary_hcd) -> No check for hcd
>      primary_hcd = hcd->primary_hcd; -> No check for hcd
>    usb_remove_hcd(hcd)
>      if (!hcd) -> Add a check by the previous commit

These hcd checks shouldn't be needed.

Thanks
Mathias