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

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Message-ID: <75592c19-309f-2626-68c9-1e74232be28e@linux.intel.com>
Date:   Fri, 20 Mar 2020 21:49:17 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        iommu@...ts.linux-foundation.org, Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>
Cc:     baolu.lu@...ux.intel.com, Raj Ashok <ashok.raj@...el.com>,
        Yi Liu <yi.l.liu@...el.com>
Subject: Re: [PATCH 2/3] iommu/vt-d: Fix mm reference leak

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@...ux.intel.com>

Acked-by: Lu Baolu <baolu.lu@...ux.intel.com>

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)
>