Re: [PATCH 1/2] iommu/vt-d: Fix PASID leak

[Lu Baolu <baolu.lu@linux.intel.com>]

Hi Fenghua,

On 2021/8/27 5:59, Fenghua Yu wrote:
> mm->pasid will be used in intel_svm_free_pasid() after load_pasid()
> during unbinding mm. Clearing it in load_pasid() will cause PASID cannot
> be freed in intel_svm_free_pasid().
> 
> Additionally mm->pasid was updated already before load_pasid() during pasid
> allocation. No need to update it again in load_pasid() during binding mm.
> 
> Don't update mm->pasid to avoid the issues in both binding mm and
> unbinding mm.
> 
> Please note that load_pasid() and its called functions will be re-written
> in upcoming re-enabling ENQCMD series. This patch tries to fix the issues
> cleanly before the re-enabling ENQCMD series.

I will remove above paragraph since it's irrelevant to the issue and the
fix itself. This fix is needed not only for ENQCMD case.

> 
> Fixes: 62ef907a045e ("iommu/vt-d: Fix PASID reference leak")

This change actually fix below commit,

Fixes: 404837741416 ("iommu/vt-d: Use iommu_sva_alloc(free)_pasid() 
helpers")

> 
> Reported-and-tested-by: Dave Jiang <dave.jiang@intel.com>
> Co-developed-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> ---
>   drivers/iommu/intel/svm.c | 3 ---
>   1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> index 4b9b3f35ba0e..ceeca633a5f9 100644
> --- a/drivers/iommu/intel/svm.c
> +++ b/drivers/iommu/intel/svm.c
> @@ -516,9 +516,6 @@ static void load_pasid(struct mm_struct *mm, u32 pasid)
>   {
>   	mutex_lock(&mm->context.lock);
>   
> -	/* Synchronize with READ_ONCE in update_pasid(). */
> -	smp_store_release(&mm->pasid, pasid);
> -
>   	/* Update PASID MSR on all CPUs running the mm's tasks. */
>   	on_each_cpu_mask(mm_cpumask(mm), _load_pasid, NULL, true);
>   
> 

I will change the commit title to "iommu/vt-d: Fix PASID leak in
intel_svm_unbind_mm()" and queued it for iommu/fix.

Best regards,
baolu
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