[PATCH v2 1/2] drm/nouveau/instmem/gk20a: fix overflow in IOVA calculation for iommu_map/unmap

[Alexey Nepomnyashih <sdl@nppct.ru>]

Fix possible overflow in the address expression used as the second
argument to iommu_map() and iommu_unmap(). Without an explicit cast,
this expression may overflow when 'r->offset' or 'i' are large. Cast
the result to unsigned long before shifting to ensure correct IOVA
computation and prevent unintended wraparound.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Cc: stable@vger.kernel.org # v4.4+
Signed-off-by: Alexey Nepomnyashih <sdl@nppct.ru>
---
 drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c b/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c
index 201022ae9214..17a0e1a46211 100644
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c
@@ -334,7 +334,7 @@ gk20a_instobj_dtor_iommu(struct nvkm_memory *memory)
 	/* Unmap pages from GPU address space and free them */
 	for (i = 0; i < node->base.mn->length; i++) {
 		iommu_unmap(imem->domain,
-			    (r->offset + i) << imem->iommu_pgshift, PAGE_SIZE);
+			    ((unsigned long)r->offset + i) << imem->iommu_pgshift, PAGE_SIZE);
 		dma_unmap_page(dev, node->dma_addrs[i], PAGE_SIZE,
 			       DMA_BIDIRECTIONAL);
 		__free_page(node->pages[i]);
@@ -472,7 +472,7 @@ gk20a_instobj_ctor_iommu(struct gk20a_instmem *imem, u32 npages, u32 align,
 
 	/* Map into GPU address space */
 	for (i = 0; i < npages; i++) {
-		u32 offset = (r->offset + i) << imem->iommu_pgshift;
+		unsigned long offset = ((unsigned long)r->offset + i) << imem->iommu_pgshift;
 
 		ret = iommu_map(imem->domain, offset, node->dma_addrs[i],
 				PAGE_SIZE, IOMMU_READ | IOMMU_WRITE,
-- 
2.43.0