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

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Message-ID: <2025081310-custodian-ashamed-3104@gregkh>
Date: Wed, 13 Aug 2025 09:09:54 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Vipin Sharma <vipinsh@...gle.com>
Cc: Pasha Tatashin <pasha.tatashin@...een.com>, pratyush@...nel.org,
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Subject: Re: [PATCH v3 29/30] luo: allow preserving memfd

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.

thanks,

greg k-h