linux-kernel - Re: [RFC PATCH 4/6] mm/memory: Add tree limit to free

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

Message-ID: <a3777992-21fc-4e55-9a5e-72b17dc86135@redhat.com>
Date: Thu, 4 Sep 2025 12:20:55 +0200
From: David Hildenbrand <david@...hat.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 maple-tree@...ts.infradead.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Vlastimil Babka <vbabka@...e.cz>,
 Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>,
 Michal Hocko <mhocko@...e.com>, Andrew Morton <akpm@...ux-foundation.org>,
 Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>,
 Charan Teja Kalla <quic_charante@...cinc.com>, shikemeng@...weicloud.com,
 kasong@...cent.com, nphamcs@...il.com, bhe@...hat.com, baohua@...nel.org,
 chrisl@...nel.org, Matthew Wilcox <willy@...radead.org>
Subject: Re: [RFC PATCH 4/6] mm/memory: Add tree limit to free_pgtables()

On 03.09.25 22:19, Liam R. Howlett wrote:
> * Lorenzo Stoakes <lorenzo.stoakes@...cle.com> [250819 15:14]:
>> On Fri, Aug 15, 2025 at 03:10:29PM -0400, Liam R. Howlett wrote:
>>> The ceiling and tree search limit need to be different arguments for the
>>> future change in the failed fork attempt.
>>>
>>> No functional changes intended.
>>>
>>> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
>>
>> (Obv. in addition to comment about broken VMA tests :P)
>>
>> I guess intent is that if we discover any page tables beyond tree_max then
>> we ought to just wipe them all out so, in effect, we don't consider
>> mappings at or past tree_max to be valid?
> 
> Actually... there are some archs that map outside the vma and they are
> valid.. I think mips? and I think lower, but yeah.. it's needed.  This
> is why prev->vm_end and next->vm_start are used as page table limits,
> afaik.  This is a serious annoyance because it frequently adds walks
> that are infrequently necessary to the vma tree.

Hm, does that still exist?

I recall something odd ... was it that gate area thingy (in_gate_area) 
we also have to handle in GUP code? The is x86/arm though, not mips.

-- 
Cheers

David / dhildenb