[RFC] mm: Fix memory corruption caused by deferred page initialization

[Aneesh Kumar K.V]

Gavin Shan <gwshan at linux.vnet.ibm.com> writes:

> [ text/plain ]
> On Sat, Mar 26, 2016 at 08:47:17PM +1100, Michael Ellerman wrote:
>>Hi Gavin,
>>
>>On Fri, 2016-25-03 at 16:05:29 UTC, Gavin Shan wrote:
>>> During deferred page initialization, the pages are moved from memblock
>>> or bootmem to buddy allocator without checking they were reserved. Those
>>> reserved pages can be reallocated to somebody else by buddy/slab allocator.
>>> It leads to memory corruption and potential kernel crash eventually.
>>
>>Can you give me a bit more detail on what the bug is?
>>
>>I haven't seen any issues on my systems, but I realise now I haven't enabled
>>DEFERRED_STRUCT_PAGE_INIT - I assumed it was enabled by default.
>>
>>How did this get tested before submission?
>
.....

> I think this patch is generic one. I guess bootmem might be supported on other
> platforms other than PPC? If that's the case, it would be fine to have the code
> fixing the bootmem bitmap if you agree. If you want me to split the patch into
> two for bootmem and memblock cases separately, I can do it absolutely. Please
> let me know your preference :-)
>

IMHO it would make it simpler if you split this into two patch. Also
avoid doing variable renames in the patch.

-aneesh