Commit 10f13d98 authored Jul 29, 2019 by Robin Murphy Committed by Greg Kroah-Hartman Sep 06, 2019

iommu/dma: Handle SG length overflow better



[ 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: 809eac54 ("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>

parent 7900374c

drivers/iommu/dma-iommu.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -493,7 +493,7 @@ 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 {