linux-kernel - Re: [PATCH v1] mm/gup: disallow FOLL_FORCE|FOLL

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Message-ID: <e2e59601-ced3-a62e-48e8-69fd24b1297e@redhat.com>
Date:   Mon, 21 Nov 2022 09:05:43 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>,
        Jason Gunthorpe <jgg@...dia.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Xu <peterx@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        syzbot+f0b97304ef90f0d0b1dc@...kaller.appspotmail.com
Subject: Re: [PATCH v1] mm/gup: disallow FOLL_FORCE|FOLL_WRITE on hugetlb
 mappings

On 31.10.22 23:13, Mike Kravetz wrote:
> On 10/31/22 13:14, Jason Gunthorpe wrote:
>> On Mon, Oct 31, 2022 at 04:25:24PM +0100, David Hildenbrand wrote:
>>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>>> Cc: Mike Kravetz <mike.kravetz@...cle.com>
>>> Cc: Peter Xu <peterx@...hat.com>
>>> Cc: John Hubbard <jhubbard@...dia.com>
>>> Cc: Jason Gunthorpe <jgg@...dia.com>
>>> Reported-by: syzbot+f0b97304ef90f0d0b1dc@...kaller.appspotmail.com
>>> Signed-off-by: David Hildenbrand <david@...hat.com>
>>> ---
>>>
>>> I assume this has been broken at least since 2014, when mm/gup.c came to
>>> life. I failed to come up with a suitable Fixes tag quickly.
>>
>> I'm worried this would break RDMA over hugetlbfs maps - which is a
>> real thing people do.
> 
> Yes, it is a real thing.  Unfortunately, I do not know exactly how it is used.
> 
>>
>> MikeK do you have test cases?
> 
> Sorry, I do not have any test cases.
> 
> I can ask one of our product groups about their usage.  But, that would
> certainly not be a comprehensive view.

With

https://lkml.kernel.org/r/20221116102659.70287-1-david@redhat.com

on it's way, the RDMA concern should be gone, hopefully.

@Andrew, can you queue this one? Thanks.

-- 
Thanks,

David / dhildenb