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Subject: Re: [PATCH] nvme: fix out of bounds access in nvme_cqe_pending
To:     Christoph Hellwig <hch@lst.de>
CC:     <wangxiongfeng2@huawei.com>, <guohanjun@huawei.com>,
        <huawei.libin@huawei.com>, <thunder.leizhen@huawei.com>,
        <tanxiaojun@huawei.com>, <xiexiuqi@huawei.com>,
        <yangyingliang@huawei.com>, <cj.chengjian@huawei.com>,
        <wxf.wang@hisilicon.com>, <keith.busch@intel.com>, <axboe@fb.com>,
        <sagi@grimberg.me>, <linux-nvme@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>
References: <1546827727-49635-1-git-send-email-yaohongbo@huawei.com>
 <20190109183920.GA22070@lst.de>
From:   Yao HongBo <yaohongbo@huawei.com>
Message-ID: <991b5090-adf7-78e1-ae19-0df94566c212@huawei.com>
Date:   Thu, 10 Jan 2019 09:54:59 +0800
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On 1/10/2019 2:39 AM, Christoph Hellwig wrote:
> On Mon, Jan 07, 2019 at 10:22:07AM +0800, Hongbo Yao wrote:
>> There is an out of bounds array access in nvme_cqe_peding().
>>
>> When enable irq_thread for nvme interrupt, there is racing between the
>> nvmeq->cq_head updating and reading.
> 
> Just curious: why did you enable this option?  Do you have a workload
> where it matters?

Yes, there were a lot of hard interrupts reported when reading the nvme disk,
the OS can not schedule and result in the soft lockup.so i enabled the irq_thread.

>> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
>> index d668682..68375d4 100644
>> --- a/drivers/nvme/host/pci.c
>> +++ b/drivers/nvme/host/pci.c
>> @@ -908,9 +908,11 @@ static void nvme_complete_cqes(struct nvme_queue *nvmeq, u16 start, u16 end)
>>  
>>  static inline void nvme_update_cq_head(struct nvme_queue *nvmeq)
>>  {
>> -	if (++nvmeq->cq_head == nvmeq->q_depth) {
>> +	if (nvmeq->cq_head == (nvmeq->q_depth - 1)) {
>>  		nvmeq->cq_head = 0;
>>  		nvmeq->cq_phase = !nvmeq->cq_phase;
>> +	} else {
>> +		++nvmeq->cq_head;
> 
> No need for the braces above, but otherwise this looks fine.  I'll apply
> it to nvme-4.21.
> 
> .
> 
 Need i send a v2 version?