[PATCH] iommu/dma: Fix MSI reservation allocation

[Marc Zyngier <maz@kernel.org>]

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")
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,
-- 
2.20.1


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