[PATCH] iommu: Use correctly sized arguments for bit field

Kees Cook
2021-12-15T23:24:37Z

The find.h APIs are designed to be used only on unsigned long arguments.
This can technically result in a over-read, but it is harmless in this
case. Regardless, fix it to avoid the warning seen under -Warray-bounds,
which we'd like to enable globally:

In file included from ./include/linux/bitmap.h:9,
from drivers/iommu/intel/iommu.c:17:
drivers/iommu/intel/iommu.c: In function 'domain_context_mapping_one':
./include/linux/find.h:119:37: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'int[1]' [-Warray-bounds]
119 | unsigned long val = *addr & GENMASK(size - 1, 0);
| ^~~~~
drivers/iommu/intel/iommu.c:2115:18: note: while referencing 'max_pde'
2115 | int pds, max_pde;
| ^~~~~~~

Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/iommu/intel/iommu.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index b6a8f3282411..99f9e8229384 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2112,10 +2112,10 @@ static void domain_exit(struct dmar_domain *domain)
*/
static inline unsigned long context_get_sm_pds(struct pasid_table *table)
{
- int pds, max_pde;
+ unsigned long pds, max_pde;

max_pde = table->max_pasid >> PASID_PDE_SHIFT;
- pds = find_first_bit((unsigned long *)&max_pde, MAX_NR_PASID_BITS);
+ pds = find_first_bit(&max_pde, MAX_NR_PASID_BITS);
if (pds < 7)
return 0;

--
2.30.2