Re: [PATCH v3 6/9] iommu/dma-iommu.c: Convert to use vm_insert_range

From: Robin Murphy
Date: Fri Dec 07 2018 - 08:47:26 EST


On 06/12/2018 18:43, Souptick Joarder wrote:
Convert to use vm_insert_range() to map range of kernel
memory to user vma.

Signed-off-by: Souptick Joarder <jrdr.linux@xxxxxxxxx>
Reviewed-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
---
drivers/iommu/dma-iommu.c | 13 +++----------
1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index d1b0475..a2c65e2 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -622,17 +622,10 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
int iommu_dma_mmap(struct page **pages, size_t size, struct vm_area_struct *vma)
{
- unsigned long uaddr = vma->vm_start;
- unsigned int i, count = PAGE_ALIGN(size) >> PAGE_SHIFT;
- int ret = -ENXIO;
+ unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
- for (i = vma->vm_pgoff; i < count && uaddr < vma->vm_end; i++) {
- ret = vm_insert_page(vma, uaddr, pages[i]);
- if (ret)
- break;
- uaddr += PAGE_SIZE;
- }
- return ret;
+ return vm_insert_range(vma, vma->vm_start,
+ pages + vma->vm_pgoff, count);

You also need to adjust count to compensate for the pages skipped by vm_pgoff, otherwise you've got an out-of-bounds dereference triggered from userspace, which is pretty high up the "not good" scale (not to mention the entire call would then propagate -EFAULT back from vm_insert_page() and thus always appear to fail for nonzero offsets).

Robin.

}
static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,