[PATCH 5.8 440/633] vfio/type1: fix dirty bitmap calculation in vfio_dma_rw

Greg Kroah-Hartman
2020-10-27T17:02:21Z

From: Yan Zhao <yan.y.zhao@intel.com>

[ Upstream commit 2c5af98592f65517170c7bcc714566590d3f7397 ]

The count of dirtied pages is not only determined by count of copied
pages, but also by the start offset.

e.g. if offset = PAGE_SIZE - 1, and *copied=2, the dirty pages count
is 2, instead of 1 or 0.

Fixes: d6a4c185660c ("vfio iommu: Implementation of ioctl for dirty pages tracking")
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/vfio/vfio_iommu_type1.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index f48f0db908a46..eb7bb14e4f62a 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -2899,7 +2899,8 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu,
* size
*/
bitmap_set(dma->bitmap, offset >> pgshift,
- *copied >> pgshift);
+ ((offset + *copied - 1) >> pgshift) -
+ (offset >> pgshift) + 1);
}
} else
*copied = copy_from_user(data, (void __user *)vaddr,
--
2.25.1