Messages in this thread | | | Date | Mon, 22 Nov 2021 19:26:14 +0100 | From | David Hildenbrand <> | Subject | Re: [PATCH] Increase default MLOCK_LIMIT to 8 MiB |
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On 22.11.21 18:55, Andrew Dona-Couch wrote: > Forgive me for jumping in to an already overburdened thread. But can > someone pushing back on this clearly explain the issue with applying > this patch?
It will allow unprivileged users to easily and even "accidentally" allocate more unmovable memory than it should in some environments. Such limits exist for a reason. And there are ways for admins/distros to tweak these limits if they know what they are doing.
> > The only concerns I've heard are that it doesn't go far enough. That > another strategy (that everyone seems to agree would be a fair bit more > effort) could potentially achieve the same goal and then some. Isn't > that exactly what's meant by "don't let perfection be the enemy of the > good"? The saying is not talking about literal perfection -- the idea is > that you make progress where you can, and that incremental progress and > broader changes are not necessarily in conflict. > > This tiny patch could be a step in the right direction. Why does this > thread need dozens of replies?
Because it does something controversial. Send controversial patches, receive many opinions, it's that simple.
This is not a step into the right direction. This is all just trying to hide the fact that we're exposing FOLL_LONGTERM usage to random unprivileged users.
Maybe we could instead try getting rid of FOLL_LONGTERM usage and the memlock limit in io_uring altogether, for example, by using mmu notifiers. But I'm no expert on the io_uring code.
-- Thanks,
David / dhildenb
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