linux-kernel - Re: [PATCH v1] kernel/fork: only call untrack_pfn

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <d63c1eb2-d026-4ef5-bb0e-531a0c390f77@redhat.com>
Date: Thu, 24 Apr 2025 14:52:07 +0200
From: David Hildenbrand <david@...hat.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
 Andrew Morton <akpm@...ux-foundation.org>, Ingo Molnar <mingo@...nel.org>,
 Dave Hansen <dave.hansen@...ux.intel.com>, Andy Lutomirski
 <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
 Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
 Rik van Riel <riel@...riel.com>, "H. Peter Anvin" <hpa@...or.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v1] kernel/fork: only call untrack_pfn_clear() on VMAs
 duplicated for fork()

>>> But maybe I misunderstand your approach :) Happy to obviously look and if
>>> not like some crazy thing just for PAT (you can understand why I would not
>>> like this) will be supportive :>)
>>
>> This is something quick (well, longer than I wish it would take) that seems to
>> work. There are smaller pat-internal cleanups to be had on top of this, and
>> the new functions shall be documented.
>>
>>
>> Observe how:
>> * We remove VM_PAT and that weird VM flags manipulation + "locked" flag
>> * We remove any traces of the nasty tracking handling from mremap+fork code
>> * Just like anon_vma_name, it hooks into vm_area_dup()/vm_area_free().
>> * We remove the page table lookup via get_pat_info()->... completely
>> * We remove the VMA parameter from PAT code completely
>> * We reduce the track/untrack/sanitize interface to 3 functions
> 
> Yeah this is all lovely!
> 
> OK this should hopefully be workable then!

Okay, let me polish that up (and see if there is any reasonable way to 
split it up), and write some doc+descriptions .. and do some more testing.

The VMA split reproducer is definitely happy with this already.

-- 
Cheers,

David / dhildenb