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>

diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
index 50e3a9fcf43e1fd4f1512bc49a21b5dfe39b88ae..b5948ba6b3b369edf0096127302e986cf7a439bc 100644 (file)
--- 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 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);