On Tue, 25 Nov 2025 17:11:18 -0800
Alex Mastro <[email protected]> wrote:
> fill_sg_entry() splits large DMA buffers into multiple scatter-gather
> entries, each holding up to UINT_MAX bytes. When calculating the DMA
> address for entries beyond the second one, the expression (i * UINT_MAX)
> causes integer overflow due to 32-bit arithmetic.
>
> This manifests when the input arg length >= 8 GiB results in looping for
> i >= 2.
>
> Fix by casting i to dma_addr_t before multiplication.
>
> Fixes: 3aa31a8bb11e ("dma-buf: provide phys_vec to scatter-gather mapping
> routine")
> Signed-off-by: Alex Mastro <[email protected]>
> ---
> More color about how I discovered this in [1] for the commit at [2]:
>
> [1] https://lore.kernel.org/all/[email protected]
> [2]
> https://lore.kernel.org/all/[email protected]
> ---
> drivers/dma-buf/dma-buf-mapping.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/dma-buf/dma-buf-mapping.c
> b/drivers/dma-buf/dma-buf-mapping.c
> index b4819811a64a..b7352e609fbd 100644
> --- a/drivers/dma-buf/dma-buf-mapping.c
> +++ b/drivers/dma-buf/dma-buf-mapping.c
> @@ -24,7 +24,7 @@ static struct scatterlist *fill_sg_entry(struct scatterlist
> *sgl, size_t length,
> * does not require the CPU list for mapping or unmapping.
> */
> sg_set_page(sgl, NULL, 0, 0);
> - sg_dma_address(sgl) = addr + i * UINT_MAX;
> + sg_dma_address(sgl) = addr + (dma_addr_t)i * UINT_MAX;
> sg_dma_len(sgl) = len;
> sgl = sg_next(sgl);
> }
>
Applied to vfio next branch for v6.19. Thanks,
Alex
