[PATCH v2] iommu/dma: Fix check for error return from iommu_map_sg_atomic()

[Niklas Schnelle]

In __iommu_dma_alloc_noncontiguous() the return value of
iommu_map_sg_atomic() is treated as an error if it is smaller than size.
Before upstream commit ad8f36e4b6b1 ("iommu: return full error code from
iommu_map_sg[_atomic]()") this simply checked if the requested size was
successfully mapped.

After that commit iommu_map_sg_atomic() may also return a negative
error value. In principle this too would be covered by the existing
check. There is one problem however, as size is of type size_t while the
return type of iommu_map_sg_atomic() is now of type ssize_t the latter gets
converted to size_t and negative error values end up as very large
positive values making the check succeed even if an error was returned.
Fix this by casting size to ssize_t.

Fixes: ad8f36e4b6b1 ("iommu: return full error code from iommu_map_sg[_atomic]()")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
---
v1 -> v2:
- Don't needlessly add a local variable

 drivers/iommu/dma-iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 09f6e1c0f9c0..80db2aa5458c 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -814,7 +814,7 @@ static struct page **__iommu_dma_alloc_noncontiguous(struct device *dev,
 	}
 
 	if (iommu_map_sg_atomic(domain, iova, sgt->sgl, sgt->orig_nents, ioprot)
-			< size)
+			< (ssize_t)size)
 		goto out_free_sg;
 
 	sgt->sgl->dma_address = iova;
-- 
2.32.0