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Re: [PATCH v7 01/14] mm: Add F_SEAL_AUTO_ALLOCATE seal to memfd
From: |
David Hildenbrand |
Subject: |
Re: [PATCH v7 01/14] mm: Add F_SEAL_AUTO_ALLOCATE seal to memfd |
Date: |
Fri, 5 Aug 2022 20:06:03 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 |
On 05.08.22 19:55, Paolo Bonzini wrote:
> On 7/21/22 11:44, David Hildenbrand wrote:
>>
>> Also, I*think* you can place pages via userfaultfd into shmem. Not
>> sure if that would count "auto alloc", but it would certainly bypass
>> fallocate().
>
> Yeah, userfaultfd_register would probably have to forbid this for
> F_SEAL_AUTO_ALLOCATE vmas. Maybe the memfile_node can be reused for
> this, adding a new MEMFILE_F_NO_AUTO_ALLOCATE flags? Then
> userfault_register would do something like
> memfile_node_get_flags(vma->vm_file) and check the result.
An alternative is to simply have the shmem allocation fail in a similar
way. Maybe it does already, I haven't checked (don't think so).
--
Thanks,
David / dhildenb