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From: Vincent Whitchurch <vincent.whitchurch@axis.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: David Gow <davidgow@google.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	Patricia Alfonso <trishalfonso@google.com>,
	Jeff Dike <jdike@addtoit.com>,
	Richard Weinberger <richard@nod.at>,
	"anton.ivanov@cambridgegreys.com"
	<anton.ivanov@cambridgegreys.com>,
	Brendan Higgins <brendanhiggins@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andrey Konovalov <andreyknvl@gmail.com>,
	Andrey Ryabinin <ryabinin.a.a@gmail.com>,
	kasan-dev <kasan-dev@googlegroups.com>,
	"linux-um@lists.infradead.org" <linux-um@lists.infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Daniel Latypov <dlatypov@google.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"kunit-dev@googlegroups.com" <kunit-dev@googlegroups.com>
Subject: Re: [PATCH v4 2/2] UML: add support for KASAN under x86_64
Date: Thu, 30 Jun 2022 14:54:34 +0200	[thread overview]
Message-ID: <20220630125434.GA20153@axis.com> (raw)
In-Reply-To: <CACT4Y+ZahTu0pGNSdZmx=4ZJHt4=mVuhxQnH_7ykDA5_fBJZVQ@mail.gmail.com>

On Thu, Jun 30, 2022 at 11:41:04AM +0200, Dmitry Vyukov wrote:
> On Thu, 30 Jun 2022 at 10:08, David Gow <davidgow@google.com> wrote:
> > diff --git a/arch/um/kernel/Makefile b/arch/um/kernel/Makefile
> > index 1c2d4b29a3d4..a089217e2f0e 100644
> > --- a/arch/um/kernel/Makefile
> > +++ b/arch/um/kernel/Makefile
> > @@ -27,6 +27,9 @@ obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
> >  obj-$(CONFIG_STACKTRACE) += stacktrace.o
> >  obj-$(CONFIG_GENERIC_PCI_IOMAP) += ioport.o
> >
> > +KASAN_SANITIZE_stacktrace.o := n
> > +KASAN_SANITIZE_sysrq.o := n
> 
> Why are these needed?
> It's helpful to leave some comments for any of *_SANITIZE:=n.
> Otherwise later it's unclear if it's due to some latent bugs, some
> inherent incompatibility, something that can be fixed, etc.

I believe I saw the stacktrace code itself triggering KASAN splats and
causing recursion when sanitization was not disabled on it.  I noticed
that other architectures disabled sanitization of their stacktrace code,
eg. ARM in commit 4d576cab16f57e1f87978f ("ARM: 9028/1: disable KASAN in
call stack capturing routines"), so I did not investigate it further.

(Note that despite the name, sysrq.c is also just stacktrace code.)

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WARNING: multiple messages have this Message-ID (diff)
From: Vincent Whitchurch <vincent.whitchurch@axis.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: David Gow <davidgow@google.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	Patricia Alfonso <trishalfonso@google.com>,
	Jeff Dike <jdike@addtoit.com>,
	Richard Weinberger <richard@nod.at>,
	"anton.ivanov@cambridgegreys.com"
	<anton.ivanov@cambridgegreys.com>,
	Brendan Higgins <brendanhiggins@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andrey Konovalov <andreyknvl@gmail.com>,
	Andrey Ryabinin <ryabinin.a.a@gmail.com>,
	kasan-dev <kasan-dev@googlegroups.com>,
	"linux-um@lists.infradead.org" <linux-um@lists.infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Daniel Latypov <dlatypov@google.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"kunit-dev@googlegroups.com" <kunit-dev@googlegroups.com>
Subject: Re: [PATCH v4 2/2] UML: add support for KASAN under x86_64
Date: Thu, 30 Jun 2022 14:54:34 +0200	[thread overview]
Message-ID: <20220630125434.GA20153@axis.com> (raw)
In-Reply-To: <CACT4Y+ZahTu0pGNSdZmx=4ZJHt4=mVuhxQnH_7ykDA5_fBJZVQ@mail.gmail.com>

On Thu, Jun 30, 2022 at 11:41:04AM +0200, Dmitry Vyukov wrote:
> On Thu, 30 Jun 2022 at 10:08, David Gow <davidgow@google.com> wrote:
> > diff --git a/arch/um/kernel/Makefile b/arch/um/kernel/Makefile
> > index 1c2d4b29a3d4..a089217e2f0e 100644
> > --- a/arch/um/kernel/Makefile
> > +++ b/arch/um/kernel/Makefile
> > @@ -27,6 +27,9 @@ obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
> >  obj-$(CONFIG_STACKTRACE) += stacktrace.o
> >  obj-$(CONFIG_GENERIC_PCI_IOMAP) += ioport.o
> >
> > +KASAN_SANITIZE_stacktrace.o := n
> > +KASAN_SANITIZE_sysrq.o := n
> 
> Why are these needed?
> It's helpful to leave some comments for any of *_SANITIZE:=n.
> Otherwise later it's unclear if it's due to some latent bugs, some
> inherent incompatibility, something that can be fixed, etc.

I believe I saw the stacktrace code itself triggering KASAN splats and
causing recursion when sanitization was not disabled on it.  I noticed
that other architectures disabled sanitization of their stacktrace code,
eg. ARM in commit 4d576cab16f57e1f87978f ("ARM: 9028/1: disable KASAN in
call stack capturing routines"), so I did not investigate it further.

(Note that despite the name, sysrq.c is also just stacktrace code.)


  reply	other threads:[~2022-06-30 12:54 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-30  8:08 [PATCH v4 1/2] mm: Add PAGE_ALIGN_DOWN macro David Gow
2022-06-30  8:08 ` David Gow
2022-06-30  8:08 ` [PATCH v4 2/2] UML: add support for KASAN under x86_64 David Gow
2022-06-30  8:08   ` David Gow
2022-06-30  9:41   ` Dmitry Vyukov
2022-06-30  9:41     ` Dmitry Vyukov
2022-06-30 12:54     ` Vincent Whitchurch [this message]
2022-06-30 12:54       ` Vincent Whitchurch
2022-06-30 13:28       ` Andrey Konovalov
2022-06-30 13:28         ` Andrey Konovalov
2022-07-01  9:08         ` David Gow
2022-07-01  9:08           ` David Gow
2022-07-01  9:16           ` Vincent Whitchurch
2022-07-01  9:16             ` Vincent Whitchurch
2022-07-01  9:43             ` David Gow
2022-07-01  9:43               ` David Gow
2022-07-01 10:04               ` Vincent Whitchurch
2022-07-01 10:04                 ` Vincent Whitchurch
2022-07-01 10:34                 ` Dmitry Vyukov
2022-07-01 10:34                   ` Dmitry Vyukov

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