Andrea Arcangeli wrote:
> On Tue, Apr 29, 2008 at 09:32:09AM -0500, Anthony Liguori wrote:
>
>> + vma = find_vma(current->mm, addr);
>> + if (vma == NULL) {
>> + get_page(bad_page);
>> + return page_to_pfn(bad_page);
>> + }
>>
>
> Here you must check vm_start address, find_vma only checks addr <
> vm_end but there's no guarantee addr >= vm_start yet.
>
Indeed.
>> +
>> + BUG_ON(!(vma->vm_flags & VM_IO));
>>
>
> For consistency we should return bad_page and not bug on, VM_IO and
> VM_PFNMAP can theoretically not be set at the same time, otherwise
> get_user_pages would be buggy checking against VM_PFNMAP|VM_IO. I
> doubt anybody isn't setting VM_IO before calling remap_pfn_range but
> anyway...
>
> Secondly the really correct check is against VM_PFNMAP. This is
> because PFNMAP is set at the same time of vm_pgoff = pfn. VM_IO is not
> even if in theory if a driver uses ->fault instead of remap_pfn_range,
> shouldn't set VM_IO and it should only set VM_RESERVED. VM_IO is about
> keeping gdb/coredump out as they could mess with the hardware if they
> read, PFNMAP is about remap_pfn_range having been called and pgoff
> pointing to the first pfn mapped at vm_start address.
>
Good point. I've updated the patch. Will send out again once I've
gotten to test it.
Regards,
Anthony Liguori
> Patch is in the right direction, way to go!
>
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