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Commit 29859aeb authored by Jean-Philippe Brucker's avatar Jean-Philippe Brucker Committed by Will Deacon
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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: default avatarJean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent fac83d29

drivers/iommu/io-pgtable-arm-v7s.c

+6 −1
Original line number Diff line number Diff line
@@ -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);