[PATCH] swiotlb: avoid potential left shift overflow

[PATCH] swiotlb: avoid potential left shift overflow

[Chao Gao]

The second operand passed to slot_addr() is declared as int or unsigned int
in all call sites. The left-shift to get the offset of a slot can overflow
if swiotlb size is larger than 4G.

Fixes: 26a7e094783d ("swiotlb: refactor swiotlb_tbl_map_single")
Signed-off-by: Chao Gao <chao.gao@intel.com>
---
 kernel/dma/swiotlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index c5a9190b218f..391b03b72978 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -579,7 +579,7 @@ 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) + ((phys_addr_t)(idx) << IO_TLB_SHIFT))
 
 /*
  * Carefully handle integer overflow which can occur when boundary_mask == ~0UL.
-- 
2.25.1

Re: [PATCH] swiotlb: avoid potential left shift overflow

[Christoph Hellwig]

On Fri, Aug 05, 2022 at 07:44:38PM +0800, Chao Gao wrote:
> The second operand passed to slot_addr() is declared as int or unsigned int
> in all call sites. The left-shift to get the offset of a slot can overflow
> if swiotlb size is larger than 4G.
> 
> Fixes: 26a7e094783d ("swiotlb: refactor swiotlb_tbl_map_single")
> Signed-off-by: Chao Gao <chao.gao@intel.com>

Can you just convert it to an inline function?  That will take care
of the typing in a much cleaner way than a cast.