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authorWill Deacon <will.deacon@arm.com>2015-08-10 17:33:36 +0100
committerDavid Brown <david.brown@arm.com>2016-02-17 10:03:22 +0000
commit11f6278900eeb0a6df245b419e404e891a117979 (patch)
treea090906c3cd2e6da5e5d0407c1411181e1465b66
parent4e7bcafd78bc5439c363ac59e36674a49726dfd8 (diff)
downloadkernel-lsk-3.18-armlt-20150916-mali.tar.gz
iommu/io-pgtable-arm: Unmap and free table when overwriting with blocklsk-3.18-armlt-20150916-mali
When installing a block mapping, we unconditionally overwrite a non-leaf PTE if we find one. However, this can cause a problem if the following sequence of events occur: (1) iommu_map called for a 4k (i.e. PAGE_SIZE) mapping at some address - We initialise the page table all the way down to a leaf entry - No TLB maintenance is required, because we're going from invalid to valid. (2) iommu_unmap is called on the mapping installed in (1) - We walk the page table to the final (leaf) entry and zero it - We only changed a valid leaf entry, so we invalidate leaf-only (3) iommu_map is called on the same address as (1), but this time for a 2MB (i.e. BLOCK_SIZE) mapping) - We walk the page table down to the penultimate level, where we find a table entry - We overwrite the table entry with a block mapping and return without any TLB maintenance and without freeing the memory used by the now-orphaned table. This last step can lead to a walk-cache caching the overwritten table entry, causing unexpected faults when the new mapping is accessed by a device. One way to fix this would be to collapse the page table when freeing the last page at a given level, but this would require expensive iteration on every map call. Instead, this patch detects the case when we are overwriting a table entry and explicitly unmaps the table first, which takes care of both freeing and TLB invalidation. Change-Id: I9215023fed90fd1076f57405f6ef9410456f0833 Cc: <stable@vger.kernel.org> Reported-by: Brian Starkey <brian.starkey@arm.com> Tested-by: Brian Starkey <brian.starkey@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Brian Starkey <brian.starkey@arm.com> Signed-off-by: Jon Medhurst <tixy@linaro.org>
-rw-r--r--drivers/iommu/io-pgtable-arm.c17
1 files changed, 16 insertions, 1 deletions
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 5a500ed..88c8b9f 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -197,6 +197,10 @@ typedef u64 arm_lpae_iopte;
static bool selftest_running = false;
+static int __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
+ unsigned long iova, size_t size, int lvl,
+ arm_lpae_iopte *ptep);
+
static int arm_lpae_init_pte(struct arm_lpae_io_pgtable *data,
unsigned long iova, phys_addr_t paddr,
arm_lpae_iopte prot, int lvl,
@@ -204,10 +208,21 @@ static int arm_lpae_init_pte(struct arm_lpae_io_pgtable *data,
{
arm_lpae_iopte pte = prot;
- /* We require an unmap first */
if (iopte_leaf(*ptep, lvl)) {
+ /* We require an unmap first */
WARN_ON(!selftest_running);
return -EEXIST;
+ } else if (iopte_type(*ptep, lvl) == ARM_LPAE_PTE_TYPE_TABLE) {
+ /*
+ * We need to unmap and free the old table before
+ * overwriting it with a block entry.
+ */
+ arm_lpae_iopte *tblp;
+ size_t sz = ARM_LPAE_BLOCK_SIZE(lvl, data);
+
+ tblp = ptep - ARM_LPAE_LVL_IDX(iova, lvl, data);
+ if (WARN_ON(__arm_lpae_unmap(data, iova, sz, lvl, tblp) != sz))
+ return -EINVAL;
}
if (data->iop.cfg.quirks & IO_PGTABLE_QUIRK_ARM_NS)