Re: [PATCH v4 2/9] arch/arm/mm/dma-mapping.c: Convert to use vm_insert_range
From: Russell King - ARM Linux
Date: Tue Dec 18 2018 - 04:38:32 EST
On Tue, Dec 18, 2018 at 01:52:09AM +0530, 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>
> arch/arm/mm/dma-mapping.c | 21 +++++++--------------
> 1 file changed, 7 insertions(+), 14 deletions(-)
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 661fe48..7cbcde5 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1582,31 +1582,24 @@ static int __arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma
> void *cpu_addr, dma_addr_t dma_addr, size_t size,
> unsigned long attrs)
> - unsigned long uaddr = vma->vm_start;
> - unsigned long usize = vma->vm_end - vma->vm_start;
> + unsigned long page_count = vma_pages(vma);
> struct page **pages = __iommu_get_pages(cpu_addr, attrs);
> unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
> unsigned long off = vma->vm_pgoff;
> + int err;
> if (!pages)
> return -ENXIO;
> - if (off >= nr_pages || (usize >> PAGE_SHIFT) > nr_pages - off)
> + if (off >= nr_pages)
> return -ENXIO;
Are you sure you can make this change?
You are restricting the offset to be within 0..nr_pages which ensures
that the initial struct page that is passed to vm_insert_range() is
valid, but I think the removal of the following check is unsafe.
Your new vm_insert_range() function only checks page_count <=
vma_pages(vma), which it will be since it _is_ vma_pages(vma). With
the removal of the second condition, there will be nothing checking
that (eg) off may be nr_pages - 1, and page_count=50, meaning that
vm_insert_range() will walk off the end of the page array.
Please take another look at this.
What about the other callsites of your new function - do they have
the same issue?
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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