Re: [PATCH] nvme: fix out of bounds access in nvme_cqe_pending

[Yao HongBo]

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?