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SubjectRe: [PATCH v3 1/9] mm: Introduce new vm_insert_range API
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On 2018-12-07 7:28 pm, Souptick Joarder wrote:
> On Fri, Dec 7, 2018 at 10:41 PM Matthew Wilcox <willy@infradead.org> wrote:
>>
>> On Fri, Dec 07, 2018 at 03:34:56PM +0000, Robin Murphy wrote:
>>>> +int vm_insert_range(struct vm_area_struct *vma, unsigned long addr,
>>>> + struct page **pages, unsigned long page_count)
>>>> +{
>>>> + unsigned long uaddr = addr;
>>>> + int ret = 0, i;
>>>
>>> Some of the sites being replaced were effectively ensuring that vma and
>>> pages were mutually compatible as an initial condition - would it be worth
>>> adding something here for robustness, e.g.:
>>>
>>> + if (page_count != vma_pages(vma))
>>> + return -ENXIO;
>>
>> I think we want to allow this to be used to populate part of a VMA.
>> So perhaps:
>>
>> if (page_count > vma_pages(vma))
>> return -ENXIO;
>
> Ok, This can be added.
>
> I think Patch [2/9] is the only leftover place where this
> check could be removed.

Right, 9/9 could also have relied on my stricter check here, but since
it's really testing whether it actually managed to allocate vma_pages()
worth of pages earlier, Matthew's more lenient version won't help for
that one. (Why privcmd_buf_mmap() doesn't clean up and return an error
as soon as that allocation loop fails, without taking the mutex under
which it still does a bunch more pointless work to only undo it again,
is a mind-boggling mystery, but that's not our problem here...)

Robin.

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