Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATH v2] scsi: scsi_dh_rdac: Avoid crash during rdac_bus_attach
To:     Bart Van Assche <bvanassche@acm.org>, <jejb@linux.ibm.com>,
        <martin.petersen@oracle.com>, <linux-scsi@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
References: <20210113063103.2698953-1-yebin10@huawei.com>
 <a1113b04-e320-a12b-5a59-ec7479d5eec1@acm.org>
From:   yebin <yebin10@huawei.com>
Message-ID: <61016887.9000200@huawei.com>
Date:   Wed, 28 Jul 2021 22:24:07 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101
 Thunderbird/38.1.0
MIME-Version: 1.0
In-Reply-To: <a1113b04-e320-a12b-5a59-ec7479d5eec1@acm.org>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk


On 2021/7/23 12:04, Bart Van Assche wrote:
> On 1/12/21 10:31 PM, Ye Bin wrote:
>>   	sdev->handler_data = NULL;
>> +	synchronize_rcu();
>>   	kfree(h);
> What is the purpose of the new synchronize_rcu() call?
Thanks for your reply.
Yes, I add new synchronize_rcu() call is to wait until *h is no longer 
in use. If free
"h" right now , mybe lead to UAF.
> If its purpose is
> to wait until *h is no longer in use, please use kfree_rcu() instead.
struct rdac_dh_data {
         struct list_head        node;
         .....
}
As rdac_dh_data.node type is "struct list_head", but  kfree_rcu the 
first parameter type is
"struct rcu_head". So we can only use synchronize_rcu() at here.
>
> Thanks,
>
> Bart.
> .
>