From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Nicolin Chen <nicoleotsuka@gmail.com>,
Sasha Levin <sashal@kernel.org>,
iommu@lists.linux-foundation.org, Joerg Roedel <jroedel@suse.de>,
Robin Murphy <robin.murphy@arm.com>
Subject: [PATCH AUTOSEL 5.2 26/44] iommu/dma: Handle SG length overflow better
Date: Tue, 20 Aug 2019 09:40:10 -0400 [thread overview]
Message-ID: <20190820134028.10829-26-sashal@kernel.org> (raw)
In-Reply-To: <20190820134028.10829-1-sashal@kernel.org>
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 379318266468c..8c02d2283d647 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -710,7 +710,7 @@ 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 {
--
2.20.1
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next parent reply other threads:[~2019-08-20 13:41 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190820134028.10829-1-sashal@kernel.org>
2019-08-20 13:40 ` Sasha Levin [this message]
2019-08-20 13:40 ` [PATCH AUTOSEL 5.2 27/44] dma-direct: don't truncate dma_required_mask to bus addressing capabilities Sasha Levin
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