It is possible, when a very large mapping uses only one
scatterlist, that padding overflows scatterlist's length field.
This results in:
1) silently wrapping the value
2) smaller than desired mappings produced by iommu_map_sg
3) leaving mapped bytes in memory (no iommu_unmap)
Address this issue by adding overflow detection for scatterlist
length field.
Fixes: 809eac54cdd6 ("iommu/dma: Implement scatterlist segment merging")
Signed-off-by: Krzysztof Karas <[email protected]>
---
v3:
* Used check_add_overflow suggested by Jason.
I decided not to include previous r-bs due to the change in the
core of this patch: overflows_type -> check_add_overflow and I
obvserved some folks have heavy preference for one or the other.
drivers/iommu/dma-iommu.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 381b60d9e7ce..1a36fd9bf10b 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1493,7 +1493,18 @@ int iommu_dma_map_sg(struct device *dev, struct
scatterlist *sg, int nents,
* time through here (i.e. before it has a meaningful value).
*/
if (pad_len && pad_len < s_length - 1) {
- prev->length += pad_len;
+ unsigned int new_pad_len;
+ /*
+ * For large mappings spanning multiple GBs we
+ * may not be able to fit all needed padding into
+ * sg->length.
+ */
+ if (check_add_overflow(prev->length, pad_len,
&new_pad_len)) {
+ ret = -EOVERFLOW;
+ goto out_restore_sg;
+ }
+
+ prev->length = new_pad_len;
iova_len += pad_len;
}
--
2.34.1
