From: Pasha Tatashin <pasha.tatashin@soleen.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Linux Doc Mailing List <linux-doc@vger.kernel.org>,
David Rientjes <rientjes@google.com>,
Paul Turner <pjt@google.com>,
weixugc@google.com, Greg Thelen <gthelen@google.com>,
Ingo Molnar <mingo@redhat.com>, Jonathan Corbet <corbet@lwn.net>,
Will Deacon <will@kernel.org>, Mike Rapoport <rppt@kernel.org>,
Kees Cook <keescook@chromium.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
masahiroy@kernel.org, Sami Tolvanen <samitolvanen@google.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>,
frederic@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
Jiri Slaby <jirislaby@kernel.org>,
Muchun Song <songmuchun@bytedance.com>,
Fusion Future <qydwhotmail@gmail.com>
Subject: Re: [PATCH v2 3/4] mm: page table check
Date: Wed, 8 Dec 2021 12:35:02 -0500 [thread overview]
Message-ID: <CA+CK2bBanZtit4Ck3wy_9bPha-Frw-SsV4UV4+GneTrcp4qN1A@mail.gmail.com> (raw)
In-Reply-To: <20211207160508.6ef48f273c1ae14c0d02c6ac@linux-foundation.org>
On Tue, Dec 7, 2021 at 7:05 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Sat, 4 Dec 2021 18:23:13 +0000 Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
>
> > Check user page table entries at the time they are added and removed.
> >
> > Allows to synchronously catch memory corruption issues related to double
> > mapping.
> >
> > When a pte for an anonymous page is added into page table, we verify that
> > this pte does not already point to a file backed page, and vice versa if
> > this is a file backed page that is being added we verify that this page
> > does not have an anonymous mapping
> >
> > We also enforce that read-only sharing for anonymous pages is allowed
> > (i.e. cow after fork). All other sharing must be for file pages.
> >
> > Page table check allows to protect and debug cases where "struct page"
> > metadata became corrupted for some reason. For example, when refcnt or
> > mapcount become invalid.
> >
> > ...
> >
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -1307,6 +1307,9 @@ config HAVE_ARCH_PFN_VALID
> > config ARCH_SUPPORTS_DEBUG_PAGEALLOC
> > bool
> >
> > +config ARCH_SUPPORTS_PAGE_TABLE_CHECK
> > + bool
> > +
>
> I guess a dependency on CONFIG_DEBUG_VM would be appropriate?
I do not think CONFIG_DEBUG_VM is needed here. We would like to have
page table check enabled on some production machines to ensure there
are no double mappings. With CONFIG_DEBUG_VM enabled that would not be
possible. For example, CONFIG_PAGE_OWNER, also uses extended struct
page entries and does not depend on CONFIG_DEBUG_VM
Pasha
next prev parent reply other threads:[~2021-12-08 17:35 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-04 18:23 [PATCH v2 0/4] page table check Pasha Tatashin
2021-12-04 18:23 ` [PATCH v2 1/4] mm: change page type prior to adding page table entry Pasha Tatashin
2021-12-04 18:23 ` [PATCH v2 2/4] mm: ptep_clear() page table helper Pasha Tatashin
2021-12-04 18:23 ` [PATCH v2 3/4] mm: page table check Pasha Tatashin
2021-12-08 0:05 ` Andrew Morton
2021-12-08 17:35 ` Pasha Tatashin [this message]
2021-12-04 18:23 ` [PATCH v2 4/4] x86: mm: add x86_64 support for " Pasha Tatashin
2021-12-21 13:09 ` [PATCH v2 0/4] " Fusion Future
2021-12-21 14:48 ` Pasha Tatashin
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