On 2022-05-07 09:52, yf.wang@mediatek.com wrote:

From: Yunfei Wang yf.wang@mediatek.com

The data type of the return value of the iommu_map_sg_atomic is ssize_t, but the data type of iova size is size_t, e.g. one is int while the other is unsigned int.

When iommu_map_sg_atomic return value is compared with iova size, it will force the signed int to be converted to unsigned int, if iova map fails and iommu_map_sg_atomic return error code is less than 0, then (ret < iova_len) is false, which will to cause not do free iova, and the master can still successfully get the iova of map fail, which is not expected.

Therefore, we need to check the return value of iommu_map_sg_atomic in two cases according to whether it is less than 0.

Heh, it's always a fun day when I have to go back to the C standard to remind myself of the usual arithmetic conversions. But indeed this seems correct, and even though the double comparisons look a little non-obvious on their own I can't think of an objectively better alternative, so:

Reviewed-by: Robin Murphy robin.murphy@arm.com

Fixes: ad8f36e4b6b1 ("iommu: return full error code from iommu_map_sg[_atomic]()") Signed-off-by: Yunfei Wang yf.wang@mediatek.com Cc: stable@vger.kernel.org # 5.15.*

---

drivers/iommu/dma-iommu.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index 09f6e1c0f9c0..2932281e93fc 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -776,6 +776,7 @@ static struct page **__iommu_dma_alloc_noncontiguous(struct device *dev, unsigned int count, min_size, alloc_sizes = domain->pgsize_bitmap; struct page **pages; dma_addr_t iova;

• ssize_t ret;

if (static_branch_unlikely(&iommu_deferred_attach_enabled) && iommu_deferred_attach(dev, domain)) @@ -813,8 +814,8 @@ static struct page **__iommu_dma_alloc_noncontiguous(struct device *dev, arch_dma_prep_coherent(sg_page(sg), sg->length); }

• if (iommu_map_sg_atomic(domain, iova, sgt->sgl, sgt->orig_nents, ioprot)

• 	< size)
  

• ret = iommu_map_sg_atomic(domain, iova, sgt->sgl, sgt->orig_nents, ioprot);
• if (ret < 0 || ret < size) goto out_free_sg;

sgt->sgl->dma_address = iova; @@ -1209,7 +1210,7 @@ static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg, * implementation - it knows better than we do. */ ret = iommu_map_sg_atomic(domain, iova, sg, nents, prot);

• if (ret < iova_len)

• if (ret < 0 || ret < iova_len) goto out_free_iova;

return __finalise_sg(dev, sg, nents, iova);