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iommu/io-pgtable-arm-v7s: Abort allocation when table address overflows the PTE 

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>
This commit is contained in:
Jean-Philippe Brucker 2018-06-19 13:52:24 +01:00 committed by Will Deacon
parent fac83d29d9
commit 29859aeb8a
1 changed files with 6 additions and 1 deletions
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7
drivers/iommu/io-pgtable-arm-v7s.c
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@ -192,6 +192,7 @@ static void *__arm_v7s_alloc_table(int lvl, gfp_t gfp,
{
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 lvl, gfp_t gfp,
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 lvl, gfp_t gfp,
* 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);