Re: [tip: x86/urgent] x86/mm/pat: Acquire init_mm write lock on collapse to avoid UAF

[Dave Hansen]

On 9/8/26 08:17, Vlastimil Babka (SUSE) wrote:
> On 9/8/26 15:58, Dave Hansen wrote:
>> On 9/8/26 02:32, Mike Rapoport wrote:
>>> I have to say I'm confused with today's batch of tip-bot emails saying Ingo
>>> applied these to x86/mm :/
>>
>> Just a reminder that we have x86/urgent which will be going to Linus
>> like today. There's also x86/mm which goes up in the next merge window..
> 
> However x86/urgent (at least as visible [1]) doesn't contain anything from
> this series, and x86/mm has everything except "Fix effective RW computation".
> 
> But tip/urgent does merge x86/mm so hopefully it means it's really going to
> Linus now-ish (and not next merge window)? It just doesn't have "urgent" in
> the branch name?

No, tip/urgent doesn't generally merge x86/mm.

>> The "Fix effective RW computation" patch is getting broken out and is
>> going to wait for the next merge window. We don't want it sitting in
>> mainline generating warnings, especially false positives like the one
>> this weekend. That's not to disparage the patch; it's overall the right
>> thing to do.
> 
> So that means adding it to x86/mm after the current one is sent as urgent?

There are a bunch of things in play:

1. The non-mm x86/urgent things
2. The CPA changes that cause actual problem
3. The CPA R^X permission check fix
4. The _PAGE_DIRTY dropping fix (separate, not CPA related)

The mm stuff is currently blocking the other stuff.

I just sent all the non-mm stuff up in a pull request to Linus.

My plan is to queue #2 and #4 back into x86/urgent once that gets
pulled. That will get the functional fixes up to Linus as soon.

I'll *then* queue #3 (the permission check) into x86/mm where it can
stew for the next ~6 weeks. It will go upstream for the next merge window.