On 12/17/2013 09:10 AM, Sasha Levin wrote:
> On 12/16/2013 07:44 PM, Bob Liu wrote:
>>
>> On 12/16/2013 07:37 AM, Sasha Levin wrote:
>>> Hi all,
>>>
>>> While fuzzing with trinity inside a KVM tools guest running latest -next
>>> kernel, I've
>>> stumbled on the following spew.
>>>
>>> This seems to be due to commit 0bf598d863e "mbind: add BUG_ON(!vma) in
>>> new_vma_page()"
>>> which added that BUG_ON.
>>
>> Could you take a try with this patch from Wanpeng Li?
>>
>> Thanks,
>> -Bob
>>
>> Subject: [PATCH] mm/mempolicy: fix !vma in new_vma_page()
>> ....
>> Signed-off-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
>> index eca4a31..73b5a35 100644
>> --- a/mm/mempolicy.c
>> +++ b/mm/mempolicy.c
>> @@ -1197,14 +1197,16 @@ static struct page *new_vma_page(struct page
>> *page, unsigned long private, int *
>> break;
>> vma = vma->vm_next;
>> }
>> +
>> + if (PageHuge(page)) {
>> + if (vma)
>> + return alloc_huge_page_noerr(vma, address, 1);
>> + else
>> + return NULL;
>> + }
>> /*
>> - * queue_pages_range() confirms that @page belongs to some vma,
>> - * so vma shouldn't be NULL.
>> + * if !vma, alloc_page_vma() will use task or system default policy
>> */
>> - BUG_ON(!vma);
>> -
>> - if (PageHuge(page))
>> - return alloc_huge_page_noerr(vma, address, 1);
>> return alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
>> }
>> #else
>>
>
> Hmm... So in essence it's mostly a revert of Naoya's patch, who seemed
> pretty certain that this
> situation shouldn't happen at all. What's the reasoning behind just
I think this assumption may not correct.
Even if
address = __vma_address(page, vma);
and
vma->start < address < vma->end;
page_address_in_vma() may still return -EFAULT because of many other
conditions in it.
As a result the while loop in new_vma_page() may end with vma=NULL.
Naoya, any idea?
--
Regards,
-Bob
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>