From: Robin Murphy robin.murphy@arm.com
[ Upstream commit ab2cbeb0ed301a9f0460078e91b09f39958212ef ]
Since scatterlist dimensions are all unsigned ints, in the relatively rare cases where a device's max_segment_size is set to UINT_MAX, then the "cur_len + s_length <= max_len" check in __finalise_sg() will always return true. As a result, the corner case of such a device mapping an excessively large scatterlist which is mergeable to or beyond a total length of 4GB can lead to overflow and a bogus truncated dma_length in the resulting segment.
As we already assume that any single segment must be no longer than max_len to begin with, this can easily be addressed by reshuffling the comparison.
Fixes: 809eac54cdd6 ("iommu/dma: Implement scatterlist segment merging") Reported-by: Nicolin Chen nicoleotsuka@gmail.com Tested-by: Nicolin Chen nicoleotsuka@gmail.com Signed-off-by: Robin Murphy robin.murphy@arm.com Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Sasha Levin sashal@kernel.org --- 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 9d1cebe7f6cbb..c87764a4e2126 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -684,7 +684,7 @@ static int __finalise_sg(struct device *dev, struct scatterlist *sg, int nents, * - and wouldn't make the resulting output segment too long */ if (cur_len && !s_iova_off && (dma_addr & seg_mask) && - (cur_len + s_length <= max_len)) { + (max_len - cur_len >= s_length)) { /* ...then concatenate it with the previous one */ cur_len += s_length; } else {