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);
}
---
base-commit: 5415d887db0e059920cb5673a32cc4d66daa280f
change-id: 20251125-dma-buf-overflow-e3253f108e36
Best regards,
--
Alex Mastro <[email protected]>
