linux-kernel - Re: [PATCH] kho: init alloc tags when restoring pages from reserved memory

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: <CAJuCfpFW+o9LR=VsCPX1XONb859G0QshWyK9NmCt43JEk9+HKw@mail.gmail.com>
Date: Sun, 11 Jan 2026 11:58:04 -0800
From: Suren Baghdasaryan <surenb@...gle.com>
To: Mike Rapoport <rppt@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, ranxiaokai627@....com, graf@...zon.com, 
	pasha.tatashin@...een.com, pratyush@...nel.org, kexec@...ts.infradead.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, ran.xiaokai@....com.cn
Subject: Re: [PATCH] kho: init alloc tags when restoring pages from reserved memory

On Sun, Jan 11, 2026 at 1:11 AM Mike Rapoport <rppt@...nel.org> wrote:
>
> On Sat, Jan 10, 2026 at 04:28:43PM -0800, Andrew Morton wrote:
> > On Fri,  9 Jan 2026 10:42:51 +0000 ranxiaokai627@....com wrote:
> >
> > > From: Ran Xiaokai <ran.xiaokai@....com.cn>
> > >
> > > Memblock pages (including reserved memory) should have their allocation
> > > tags initialized to CODETAG_EMPTY via clear_page_tag_ref() before being
> > > released to the page allocator. When kho restores pages through
> > > kho_restore_page(), missing this call causes mismatched
> > > allocation/deallocation tracking and warning message:
> > > alloc_tag was not set.
> > >
> > > Add missing clear_page_tag_ref() annotation in kho_restore_page() to
> > > fix this.
> >
> > Great, thanks.
> >
> > It would be helpful to quote that warning message in the patch
> > changelog, please.
> >
> > > --- a/kernel/liveupdate/kexec_handover.c
> > > +++ b/kernel/liveupdate/kexec_handover.c
> > > @@ -268,6 +268,7 @@ static struct page *kho_restore_page(phys_addr_t phys, bool is_folio)
> > >     else
> > >             kho_init_pages(page, nr_pages);
> > >
> > > +   clear_page_tag_ref(page);
> > >     adjust_managed_page_count(page, nr_pages);
> > >     return page;
> > >  }
> >
> > Warning splats are pretty bad and it's desirable to fix this in
> > previous kernel versions.
> >
> > To do that it's best for us to identify which kernel version(s) should
> > be patched, via a Fixes: tag in the changelog.
> >
> > From a quick look, it appears that Pratyush's 12b9a2c05d1b ("kho:
> > initialize tail pages for higher order folios properly") is a suitable
> > anchor, what do people think?
>
> I think it should be even earlier:
> fc33e4b44b27 ("kexec: enable KHO support for memory preservation")

I agree.

>
> > Meanwhile I'll queue this up for some testing while awaiting maintainer
> > feedback.
>
> --
> Sincerely yours,
> Mike.