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 amastro@fb.com --- More color about how I discovered this in [1] for the commit at [2]:
[1] https://lore.kernel.org/all/aSZHO6otK0Heh+Qj@devgpu015.cco6.facebook.com [2] https://lore.kernel.org/all/20251120-dmabuf-vfio-v9-6-d7f71607f371@nvidia.co... --- 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); }
--- base-commit: 5415d887db0e059920cb5673a32cc4d66daa280f change-id: 20251125-dma-buf-overflow-e3253f108e36
Best regards,