Re: [syzbot] [mm?] WARNING in __folio_rmap_sanity_checks (2)

David Hildenbrand
2025-01-10T16:31:42Z

On 10.01.25 17:27, Matthew Wilcox wrote:
> On Fri, Jan 10, 2025 at 05:19:54PM +0100, David Hildenbrand wrote:
>> On 10.01.25 17:14, Matthew Wilcox wrote:
>>> On Fri, Jan 10, 2025 at 04:48:03PM +0100, David Hildenbrand wrote:
>>>> If I would have to guess, I would assume that we have a refcount issue such
>>>> that we succeed in splitting a folio while concurrently mapping it.
>>>
>>> That would seem hard to accomplish, because both hold the folio lock,
>>> so it wouldn't be just a refcount bug but also a locking bug. Not sure
>>> what this is though.
>>
>> Yeah, but we also have
>>
>> https://lkml.kernel.org/r/6774bf44.050a0220.25abdd.098a.GAE@google.com
>
> That one is a UAF on the vma, so it's either a different issue, or the
> problem is with the VMA refcount/lookup/..., not the folio refcount.
> cc'ing the relevant maintainers.

Agreed, it's all a bit confusing.

--
Cheers,

David / dhildenb