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: <2025081351-tinsel-sprinkler-af77@gregkh>
Date: Wed, 13 Aug 2025 14:14:23 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Pratyush Yadav <pratyush@...nel.org>
Cc: 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, jgg@...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 at 02:02:07PM +0200, Pratyush Yadav wrote:
> On Wed, Aug 13 2025, Greg KH wrote:
> 
> > On Tue, Aug 12, 2025 at 11:34:37PM -0700, Vipin Sharma wrote:
> >> On 2025-08-07 01:44:35, Pasha Tatashin wrote:
> >> > From: Pratyush Yadav <ptyadav@...zon.de>
> >> > +static void memfd_luo_unpreserve_folios(const struct memfd_luo_preserved_folio *pfolios,
> >> > +					unsigned int nr_folios)
> >> > +{
> >> > +	unsigned int i;
> >> > +
> >> > +	for (i = 0; i < nr_folios; i++) {
> >> > +		const struct memfd_luo_preserved_folio *pfolio = &pfolios[i];
> >> > +		struct folio *folio;
> >> > +
> >> > +		if (!pfolio->foliodesc)
> >> > +			continue;
> >> > +
> >> > +		folio = pfn_folio(PRESERVED_FOLIO_PFN(pfolio->foliodesc));
> >> > +
> >> > +		kho_unpreserve_folio(folio);
> >> 
> >> This one is missing WARN_ON_ONCE() similar to the one in
> >> memfd_luo_preserve_folios().
> >
> > So you really want to cause a machine to reboot and get a CVE issued for
> > this, if it could be triggered?  That's bold :)
> >
> > Please don't.  If that can happen, handle the issue and move on, don't
> > crash boxes.
> 
> Why would a WARN() crash the machine? That is what BUG() does, not
> WARN().

See 'panic_on_warn' which is enabled in a few billion Linux systems
these days :(