Re: [PATCH] iommu/dma: Fix MSI reservation allocation

[Auger Eric <eric.auger@redhat.com>]

Hi Marc,
On 3/3/20 12:51 PM, Marc Zyngier wrote:
> The way cookie_init_hw_msi_region() allocates the iommu_dma_msi_page
> structures doesn't match the way iommu_put_dma_cookie() frees them.
> 
> The former performs a single allocation of all the required structures,
> while the latter tries to free them one at a time. It doesn't quite
> work for the main use case (the GICv3 ITS where the range is 64kB)
> when the base ganule size is 4kB.
> 
> This leads to a nice slab corruption on teardown, which is easily
> observable by simply creating a VF on a SRIOV-capable device, and
> tearing it down immediately (no need to even make use of it).
> 
> Fix it by allocating iommu_dma_msi_page structures one at a time.
> 
> Fixes: 7c1b058c8b5a3 ("iommu/dma: Handle IOMMU API reserved regions")
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric

> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Joerg Roedel <jroedel@suse.de>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: stable@vger.kernel.org
> ---
>  drivers/iommu/dma-iommu.c | 36 ++++++++++++++++++++++++------------
>  1 file changed, 24 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index a2e96a5fd9a7..01fa64856c12 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -171,25 +171,37 @@ static int cookie_init_hw_msi_region(struct iommu_dma_cookie *cookie,
>  		phys_addr_t start, phys_addr_t end)
>  {
>  	struct iova_domain *iovad = &cookie->iovad;
> -	struct iommu_dma_msi_page *msi_page;
> -	int i, num_pages;
> +	struct iommu_dma_msi_page *msi_page, *tmp;
> +	int i, num_pages, ret = 0;
> +	phys_addr_t base;
>  
> -	start -= iova_offset(iovad, start);
> +	base = start -= iova_offset(iovad, start);
>  	num_pages = iova_align(iovad, end - start) >> iova_shift(iovad);
>  
> -	msi_page = kcalloc(num_pages, sizeof(*msi_page), GFP_KERNEL);
> -	if (!msi_page)
> -		return -ENOMEM;
> -
>  	for (i = 0; i < num_pages; i++) {
> -		msi_page[i].phys = start;
> -		msi_page[i].iova = start;
> -		INIT_LIST_HEAD(&msi_page[i].list);
> -		list_add(&msi_page[i].list, &cookie->msi_page_list);
> +		msi_page = kmalloc(sizeof(*msi_page), GFP_KERNEL);
> +		if (!msi_page) {
> +			ret = -ENOMEM;
> +			break;
> +		}
> +		msi_page->phys = start;
> +		msi_page->iova = start;
> +		INIT_LIST_HEAD(&msi_page->list);
> +		list_add(&msi_page->list, &cookie->msi_page_list);
>  		start += iovad->granule;
>  	}
>  
> -	return 0;
> +	if (ret) {
> +		list_for_each_entry_safe(msi_page, tmp,
> +					 &cookie->msi_page_list, list) {
> +			if (msi_page->phys >= base && msi_page->phys < start) {
> +				list_del(&msi_page->list);
> +				kfree(msi_page);
> +			}
> +		}
> +	}
> +
> +	return ret;
>  }
>  
>  static int iova_reserve_pci_windows(struct pci_dev *dev,
>