Security is the primary case where we have historically closed uAPI
items.
As this patch
1) Does not tackle GUP-fast
2) Does not take care of !FOLL_LONGTERM
I am not convinced by the security argument in regard to this patch.
If we want to sells this as a security thing, we have to block it
*completely* and then CC stable.
Regarding GUP-fast, to fix the issue there as well, I guess we could do
something similar as I did in gup_must_unshare():
If we're in GUP-fast (no VMA), and want to pin a !anon page writable,
fallback to ordinary GUP. IOW, if we don't know, better be safe.
Of course, this would prevent hugetlb/shmem from getting pinned writable
during gup-fast. Unless we're able to whitelist them somehow in there.
For FOLL_LONGTERM it might fairly uncontroversial. For everything else
I'm not sure if there could be undesired side-effects.
--
Thanks,
David / dhildenb
