Messages in this thread | | | Date | Tue, 24 Jan 2023 11:24:06 +0100 | Subject | Re: [PATCH v7 0/8] iov_iter: Improve page extraction (ref, pin or just list) | From | David Hildenbrand <> |
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On 23.01.23 18:25, Jan Kara wrote: > On Mon 23-01-23 16:42:56, Matthew Wilcox wrote: >> On Mon, Jan 23, 2023 at 04:38:47PM +0000, David Howells wrote: >>> Matthew Wilcox <willy@infradead.org> wrote: >>> Also you only mention DIO read - but what about "start DIO write; fork(); touch >>> buffer" in the parent - now the write buffer belongs to the child and they can >>> affect the parent's write. >> >> I'm struggling to see the problem here. If the child hasn't exec'd, the >> parent and child are still in the same security domain. The parent >> could have modified the buffer before calling fork(). > > Sadly they are not. Android in particular starts applications by forking > one big binary (zygote) that has multiple apps linked together and relies > on the fact the child cannot influence the parent after the fork. We've > already had CVEs with GUP & COW & fork due to this. David Hildebrand has a > lot of memories regarding this I believe ;)
:)
Once FOLL_PIN is used most of the issues go away and we don't have to play any games with VM flags or similar ...
With FOLL_PIN, I consider anon a solved problem and not worth any new fancy ideas.
-- Thanks,
David / dhildenb
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