Re: [PATCH] vhost: Fix Segmentation fault of NULL address

[Linhaifeng <haifeng.lin-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>]

On 2015/3/26 15:58, Qiu, Michael wrote:
> On 3/26/2015 3:52 PM, Xie, Huawei wrote:
>> On 3/26/2015 3:05 PM, Qiu, Michael wrote:
>>> Function gpa_to_vva() could return zero, while this will lead
>>> a Segmentation fault.
>>>
>>> This patch is to fix this issue.
>>>
>>> Signed-off-by: Michael Qiu <michael.qiu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
>>> ---
>>>  lib/librte_vhost/vhost_rxtx.c | 3 +++
>>>  1 file changed, 3 insertions(+)
>>>
>>> diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
>>> index 535c7a1..23c8acb 100644
>>> --- a/lib/librte_vhost/vhost_rxtx.c
>>> +++ b/lib/librte_vhost/vhost_rxtx.c
>>> @@ -587,6 +587,9 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
>>>  
>>>  		/* Buffer address translation. */
>>>  		vb_addr = gpa_to_vva(dev, desc->addr);
>>> +		if (!vb_addr)
>>> +			return entry_success;
>>> +
>> Firstly we should add check for all gpa_to_vva translation, and do
>> reporting and cleanup on error. We should avoid the case that some buggy
>> or malicious guest virtio driver gives us an invalid GPA(for example,
>> GPA for some MMIO space) and crash our vhost process.
> 
> Yes, agree, I will do this for next version.
> 
>> As we discuss, you meet segfault here, but our virtio PMD shouldn't give
>> us the GPA that has no translation, so we should root cause first and
> 
> Yes, root cause is very important, but it will spend lots time, and I
> think we could be possible to apply this first(All check version).
> 

How to deal with invalid address but not NULL?

> Thanks,
> Michael
>> fix the problem, and then submit the patch checking all gpa_to_vva
>> translation.
>>
>> -Huawei
>>>  		/* Prefetch buffer address. */
>>>  		rte_prefetch0((void *)(uintptr_t)vb_addr);
>>>  
>>
> 
> 
>