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Subject[PATCH 4.18 018/235] iommu/io-pgtable-arm-v7s: Abort allocation when table address overflows the PTE
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>

[ Upstream commit 29859aeb8a6ea17ba207933a81b6b77b4d4df81a ]

When run on a 64-bit system in selftest, the v7s driver may obtain page
table with physical addresses larger than 32-bit. Level-2 tables are 1KB
and are are allocated with slab, which doesn't accept the GFP_DMA32
flag. Currently map() truncates the address written in the PTE, causing
iova_to_phys() or unmap() to access invalid memory. Kasan reports it as
a use-after-free. To avoid any nasty surprise, test if the physical
address fits in a PTE before returning a new table. 32-bit systems,
which are the main users of this page table format, shouldn't see any
difference.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/iommu/io-pgtable-arm-v7s.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

--- a/drivers/iommu/io-pgtable-arm-v7s.c
+++ b/drivers/iommu/io-pgtable-arm-v7s.c
@@ -192,6 +192,7 @@ static void *__arm_v7s_alloc_table(int l
{
struct io_pgtable_cfg *cfg = &data->iop.cfg;
struct device *dev = cfg->iommu_dev;
+ phys_addr_t phys;
dma_addr_t dma;
size_t size = ARM_V7S_TABLE_SIZE(lvl);
void *table = NULL;
@@ -200,6 +201,10 @@ static void *__arm_v7s_alloc_table(int l
table = (void *)__get_dma_pages(__GFP_ZERO, get_order(size));
else if (lvl == 2)
table = kmem_cache_zalloc(data->l2_tables, gfp | GFP_DMA);
+ phys = virt_to_phys(table);
+ if (phys != (arm_v7s_iopte)phys)
+ /* Doesn't fit in PTE */
+ goto out_free;
if (table && !(cfg->quirks & IO_PGTABLE_QUIRK_NO_DMA)) {
dma = dma_map_single(dev, table, size, DMA_TO_DEVICE);
if (dma_mapping_error(dev, dma))
@@ -209,7 +214,7 @@ static void *__arm_v7s_alloc_table(int l
* address directly, so if the DMA layer suggests otherwise by
* translating or truncating them, that bodes very badly...
*/
- if (dma != virt_to_phys(table))
+ if (dma != phys)
goto out_unmap;
}
kmemleak_ignore(table);

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