iommu/dma: Fix MSI reservation allocation

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 granule 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). Fortunately, this only affects systems where the ITS isn't translated by the SMMU, which are both rare and non-standard.

Fix it by allocating iommu_dma_msi_page structures one at a time.

Fixes 7c1b058c8b5a3 ("iommu/dma: Handle IOMMU API reserved regions")

Signed-off-by Marc Zyngier <[email protected]>

Reviewed-by Eric Auger <[email protected]>

Cc Robin Murphy <[email protected]>

Cc Joerg Roedel <[email protected]>

Cc Will Deacon <[email protected]>

Cc [email protected]

---
* From v1:
- Got rid of the superfluous error handling (Robin)
- Clarified that it only affects a very small set of systems
- Added Eric's RB (which I assume still stands)

  drivers/iommu/dma-iommu.c | 16 ++++++++--------
  1 file changed, 8 insertions(+), 8 deletions(-)

drivers/iommu/dma-iommu.c +8 -8

index a2e96a5fd9a7..ba128d1cdaee 100644
@@ -177,15 +177,15 @@ static int cookie_init_hw_msi_region(struct iommu_dma_cookie *cookie,
  	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)
+			return -ENOMEM;
+
+		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;
  	}
 

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 granule 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). Fortunately, this only affects systems where the ITS isn't translated by the SMMU, which are both rare and non-standard.

Fix it by allocating iommu_dma_msi_page structures one at a time.

Fixes 7c1b058c8b5a3 ("iommu/dma: Handle IOMMU API reserved regions")

Signed-off-by Marc Zyngier <[email protected]>

Reviewed-by Eric Auger <[email protected]>

Cc Robin Murphy <[email protected]>

Cc Joerg Roedel <[email protected]>

Cc Will Deacon <[email protected]>

Cc [email protected]