linux-kernel - Re: [PATCH v3 29/30] luo: allow preserving memfd

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: <mafs07bz7wdfk.fsf@kernel.org>
Date: Wed, 13 Aug 2025 15:37:03 +0200
From: Pratyush Yadav <pratyush@...nel.org>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: Jason Gunthorpe <jgg@...dia.com>,  Pratyush Yadav <pratyush@...nel.org>,
  Vipin Sharma <vipinsh@...gle.com>,  Pasha Tatashin
 <pasha.tatashin@...een.com>,  jasonmiu@...gle.com,  graf@...zon.com,
  changyuanl@...gle.com,  rppt@...nel.org,  dmatlack@...gle.com,
  rientjes@...gle.com,  corbet@....net,  rdunlap@...radead.org,
  ilpo.jarvinen@...ux.intel.com,  kanie@...ux.alibaba.com,
  ojeda@...nel.org,  aliceryhl@...gle.com,  masahiroy@...nel.org,
  akpm@...ux-foundation.org,  tj@...nel.org,  yoann.congal@...le.fr,
  mmaurer@...gle.com,  roman.gushchin@...ux.dev,  chenridong@...wei.com,
  axboe@...nel.dk,  mark.rutland@....com,  jannh@...gle.com,
  vincent.guittot@...aro.org,  hannes@...xchg.org,
  dan.j.williams@...el.com,  david@...hat.com,  joel.granados@...nel.org,
  rostedt@...dmis.org,  anna.schumaker@...cle.com,  song@...nel.org,
  zhangguopeng@...inos.cn,  linux@...ssschuh.net,
  linux-kernel@...r.kernel.org,  linux-doc@...r.kernel.org,
  linux-mm@...ck.org,  tglx@...utronix.de,  mingo@...hat.com,
  bp@...en8.de,  dave.hansen@...ux.intel.com,  x86@...nel.org,
  hpa@...or.com,  rafael@...nel.org,  dakr@...nel.org,
  bartosz.golaszewski@...aro.org,  cw00.choi@...sung.com,
  myungjoo.ham@...sung.com,  yesanishhere@...il.com,
  Jonathan.Cameron@...wei.com,  quic_zijuhu@...cinc.com,
  aleksander.lobakin@...el.com,  ira.weiny@...el.com,
  andriy.shevchenko@...ux.intel.com,  leon@...nel.org,  lukas@...ner.de,
  bhelgaas@...gle.com,  wagi@...nel.org,  djeffery@...hat.com,
  stuart.w.hayes@...il.com,  lennart@...ttering.net,  brauner@...nel.org,
  linux-api@...r.kernel.org,  linux-fsdevel@...r.kernel.org,
  saeedm@...dia.com,  ajayachandra@...dia.com,  parav@...dia.com,
  leonro@...dia.com,  witu@...dia.com
Subject: Re: [PATCH v3 29/30] luo: allow preserving memfd

On Wed, Aug 13 2025, Greg KH wrote:

> On Wed, Aug 13, 2025 at 09:41:40AM -0300, Jason Gunthorpe wrote:
[...]
>> Use the warn ons. Make sure they can't be triggered by userspace. Use
>> them to detect corruption/malfunction in the kernel.
>> 
>> In this case if kho_unpreserve_folio() fails in this call chain it
>> means some error unwind is wrongly happening out of sequence, and we
>> are now forced to leak memory. Unwind is not something that userspace
>> should be controlling, so of course we want a WARN_ON here.
>
> "should be" is the key here.  And it's not obvious from this patch if
> that's true or not, which is why I mentioned it.
>
> I will keep bringing this up, given the HUGE number of CVEs I keep
> assigning each week for when userspace hits WARN_ON() calls until that
> flow starts to die out either because we don't keep adding new calls, OR
> we finally fix them all.  Both would be good...

Out of curiosity, why is hitting a WARN_ON() considered a vulnerability?
I'd guess one reason is overwhelming system console which can cause a
denial of service, but what about WARN_ON_ONCE() or WARN_RATELIMIT()?

-- 
Regards,
Pratyush Yadav