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

["Qiu, Michael" <michael.qiu@intel.com>]

On 3/26/2015 4:29 PM, Linhaifeng wrote:
>
> 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@intel.com>
>>>> ---
>>>>  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?

The problem is how do you know if it is a valid addres?

Thanks,
Michael
>
>> 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);
>>>>  
>>
>>
>