[PATCH RFC v1 7/7] swiotlb: fix the slot_addr() overflow

[Dongli Zhang <dongli.zhang@xxxxxxxxxx>]

Since the type of swiotlb slot index is a signed integer, the
"((idx) << IO_TLB_SHIFT)" will returns incorrect value. As a result, the
slot_addr() returns a value which is smaller than the expected one.

E.g., the 'tlb_addr' generated in swiotlb_tbl_map_single() may return a
value smaller than the expected one. As a result, the swiotlb_bounce()
will access a wrong swiotlb slot.

Cc: Konrad Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Joe Jin <joe.jin@xxxxxxxxxx>
Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
---
 kernel/dma/swiotlb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 0dcdd25ea95d..c64e557de55c 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -531,7 +531,8 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t 
tlb_addr, size_t size
        }
 }
 
-#define slot_addr(start, idx)  ((start) + ((idx) << IO_TLB_SHIFT))
+#define slot_addr(start, idx)  ((start) + \
+                               (((unsigned long)idx) << IO_TLB_SHIFT))
 
 /*
  * Carefully handle integer overflow which can occur when boundary_mask == 
~0UL.
-- 
2.17.1