Re: [PATCH 2/3] iommu/vt-d: Fix mm reference leak

[Lu Baolu]

On 2020/3/20 12:32, Jacob Pan wrote:
> Move canonical address check before mmget_not_zero() to avoid mm
> reference leak.
>
> Fixes: 9d8c3af31607 ("iommu/vt-d: IOMMU Page Request needs to check if
> address is canonical.")
>
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>

Acked-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

Best regards,
baolu

> ---
>   drivers/iommu/intel-svm.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> index 1483f1845762..56253c59ca10 100644
> --- a/drivers/iommu/intel-svm.c
> +++ b/drivers/iommu/intel-svm.c
> @@ -861,14 +861,15 @@ static irqreturn_t prq_event_thread(int irq, void *d)
>   		 * any faults on kernel addresses. */
>   		if (!svm->mm)
>   			goto bad_req;
> -		/* If the mm is already defunct, don't handle faults. */
> -		if (!mmget_not_zero(svm->mm))
> -			goto bad_req;
>   
>   		/* If address is not canonical, return invalid response */
>   		if (!is_canonical_address(address))
>   			goto bad_req;
>   
> +		/* If the mm is already defunct, don't handle faults. */
> +		if (!mmget_not_zero(svm->mm))
> +			goto bad_req;
> +
>   		down_read(&svm->mm->mmap_sem);
>   		vma = find_extend_vma(svm->mm, address);
>   		if (!vma || address < vma->vm_start)