iommu/io-pgtable-arm: Check for leaf entry before dereferencing it

Do a check for already installed leaf entry at the current level before
dereferencing it in order to avoid walking the page table down with
wrong pointer to the next level.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index feacc54bec68..f9bc6ebb8140 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -335,8 +335,12 @@ static int __arm_lpae_map(struct arm_lpae_io_pgtable *data, unsigned long iova,
                 if (cfg->quirks & IO_PGTABLE_QUIRK_ARM_NS)
                         pte |= ARM_LPAE_PTE_NSTABLE;
                 __arm_lpae_set_pte(ptep, pte, cfg);
-        } else {
+        } else if (!iopte_leaf(pte, lvl)) {
                 cptep = iopte_deref(pte, data);
+        } else {
+                /* We require an unmap first */
+                WARN_ON(!selftest_running);
+                return -EEXIST;
         }
 
         /* Rinse, repeat */