linux-kernel - Re: [PATCH v13 2/5] arm64: add support for ARCH_HAS_COPY

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] [day] [month] [year] [list]

Message-ID: <Z+bXE7UNWFLEfhQC@e129823.arm.com>
Date: Fri, 28 Mar 2025 17:06:27 +0000
From: Yeoreum Yun <yeoreum.yun@....com>
To: Tong Tiangen <tongtiangen@...wei.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Mark Rutland <mark.rutland@....com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
	Will Deacon <will@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	James Morse <james.morse@....com>,
	Robin Murphy <robin.murphy@....com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Vincenzo Frascino <vincenzo.frascino@....com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	"Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
	"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	kasan-dev@...glegroups.com, wangkefeng.wang@...wei.com,
	Guohanjun <guohanjun@...wei.com>
Subject: Re: [PATCH v13 2/5] arm64: add support for ARCH_HAS_COPY_MC

Hi,

>
>
> 在 2025/2/13 0:21, Catalin Marinas 写道:
> > (catching up with old threads)
> >
> > On Mon, Dec 09, 2024 at 10:42:54AM +0800, Tong Tiangen wrote:
> > > For the arm64 kernel, when it processes hardware memory errors for
> > > synchronize notifications(do_sea()), if the errors is consumed within the
> > > kernel, the current processing is panic. However, it is not optimal.
> > >
> > > Take copy_from/to_user for example, If ld* triggers a memory error, even in
> > > kernel mode, only the associated process is affected. Killing the user
> > > process and isolating the corrupt page is a better choice.
> >
> > I agree that killing the user process and isolating the page is a better
> > choice but I don't see how the latter happens after this patch. Which
> > page would be isolated?
>
> The SEA is triggered when the page with hardware error is read. After
> that, the page is isolated in memory_failure() (mf). The processing of
> mf is mentioned in the comments of do_sea().
>
> /*
>  * APEI claimed this as a firmware-first notification.
>  * Some processing deferred to task_work before ret_to_user().
>  */
>
> Some processing include mf.
>
> >
> > > Add new fixup type EX_TYPE_KACCESS_ERR_ZERO_MEM_ERR to identify insn
> > > that can recover from memory errors triggered by access to kernel memory,
> > > and this fixup type is used in __arch_copy_to_user(), This make the regular
> > > copy_to_user() will handle kernel memory errors.
> >
> > Is the assumption that the error on accessing kernel memory is
> > transient? There's no way to isolate the kernel page and also no point
> > in isolating the destination page either.
>
> Yes, it's transient, the kernel page in mf can't be isolated, the
> transient access (ld) of this kernel page is currently expected to kill
> the user-mode process to avoid error spread.

I'm not sure about how this works.
IIUC, the memory_failure() wouldn't kill any process if page which
raises sea is kernel page (because this wasn't mapped).

But, to mark the kernel page as posision, I think it also need to call
apei_claim_sea() in !user_mode().
What about calling the apei_claim_sea() when fix_exception_me()
successed only in !user_mode() case?

Thanks.
>
> The SEA processes synchronization errors. Only hardware errors on the
> source page can be detected (Through synchronous ld insn) and processed.
> The destination page cannot be processed.
>
> >
>