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SubjectRe: [PATCH 1/1] iommu/vtd: Fix NULL pointer dereference in prq_event_thread()
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Hi Yi,

On 11/5/18 1:21 PM, Liu, Yi L wrote:
> Hi Baolu,
>
>> From: iommu-bounces@lists.linux-foundation.org [mailto:iommu-
>> bounces@lists.linux-foundation.org] On Behalf Of Lu Baolu
>> Sent: Monday, November 5, 2018 10:19 AM
>> To: Joerg Roedel <joro@8bytes.org>; David Woodhouse <dwmw2@infradead.org>
>> Cc: Raj, Ashok <ashok.raj@intel.com>; linux-kernel@vger.kernel.org;
>> iommu@lists.linux-foundation.org
>> Subject: [PATCH 1/1] iommu/vtd: Fix NULL pointer dereference in prq_event_thread()
>>
>> When handling page request without pasid event, go to "no_pasid"
>> branch instead of "bad_req". Otherwise, a NULL pointer deference will happen there.
>>
>> Cc: Ashok Raj <ashok.raj@intel.com>
>> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
>> Cc: Sohil Mehta <sohil.mehta@intel.com>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> ---
>> drivers/iommu/intel-svm.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c index
>> db301efe126d..887150907526 100644
>> --- a/drivers/iommu/intel-svm.c
>> +++ b/drivers/iommu/intel-svm.c
>> @@ -595,7 +595,7 @@ static irqreturn_t prq_event_thread(int irq, void *d)
>> pr_err("%s: Page request without PASID: %08llx %08llx\n",
>> iommu->name, ((unsigned long long *)req)[0],
>> ((unsigned long long *)req)[1]);
>> - goto bad_req;
>> + goto no_pasid;
>> }
>>
>> if (!svm || svm->pasid != req->pasid) {
>> --
>
> I'm afraid it is still necessary to goto "bad_req". The following code behind
> "bad_req" will trigger fault_cb registered by in-kernel drivers. It is reasonable
> that PRQ without PASID can be handled by such callbacks. So I would suggest
> to keep the existing logic.

A page fault without a pasid is triggered by a DMA transfer without
PASID. It doesn't relate to the SVM functionality hence there's no
@svm or @sdev related to it. It's unnecessary to report it to the
drivers as far as I can see.

Best regards,
Lu Baolu

>
> if (sdev && sdev->ops && sdev->ops->fault_cb) {
> int rwxp = (req->rd_req << 3) | (req->wr_req << 2) |
> (req->exe_req << 1) | (req->priv_req);
> sdev->ops->fault_cb(sdev->dev, req->pasid, req->addr, req->private, rwxp, result);
> }
>
> Thanks,
> Yi Liu
>

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