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SubjectRe: [PATCH 02/21] arm64/iommu: improve mmap bounds checking
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On 07/04/2019 07:59, Christoph Hellwig wrote:
> On Fri, Apr 05, 2019 at 06:30:52PM +0100, Robin Murphy wrote:
>> On 27/03/2019 08:04, Christoph Hellwig wrote:
>>> The nr_pages checks should be done for all mmap requests, not just those
>>> using remap_pfn_range.
>>
>> Hmm, the logic in iommu_dma_mmap() inherently returns an error for the "off
>>> = nr_pages" case already. It's also supposed to be robust against the
>> "vma_pages(vma) > nr_pages - off" condition, although by making the partial
>> mapping and treating it as a success, rather than doing nothing and
>> returning an error. What's the exact motivation here?
>
> Have one error check at the front of the function that is identical
> to the mmap checks in the other dma_map_ops instances so that:
>
> a) we get the same error behavior for partial requests everywhere
> b) we can lift these checks into common code in the next round.
>

Fair enough, but in that case why isn't the dma_mmap_from_coherent()
path also covered?

Robin.

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