Re: [RFC PATCH] UML: add support for KASAN under x86_64

From: Patricia Alfonso <trishalfonso@google.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Jeff Dike <jdike@addtoit.com>,
	Richard Weinberger <richard@nod.at>,
	anton.ivanov@cambridgegreys.com,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	David Gow <davidgow@google.com>,
	Brendan Higgins <brendanhiggins@google.com>,
	linux-um@lists.infradead.org,
	kasan-dev <kasan-dev@googlegroups.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH] UML: add support for KASAN under x86_64
Date: Thu, 13 Feb 2020 14:55:59 -0800	[thread overview]
Message-ID: <CAKFsvUKun6HOk_9ocZ81YebEp90jr3WsAah24HDQQQqY9eamjg@mail.gmail.com> (raw)
In-Reply-To: <CACT4Y+ZJeABriqRZkThVa-MNDBwe7cH=Hmq1vonNmyCTMZOu6w@mail.gmail.com>

On Wed, Feb 12, 2020 at 9:40 PM 'Dmitry Vyukov' via kasan-dev
<kasan-dev@googlegroups.com> wrote:
>
> On Wed, Feb 12, 2020 at 11:25 PM Patricia Alfonso
> <trishalfonso@google.com> wrote:
> > > On Wed, Feb 12, 2020 at 1:19 AM Patricia Alfonso
> > > <trishalfonso@google.com> wrote:
> > > >
> > > > On Thu, Jan 16, 2020 at 12:53 AM Dmitry Vyukov <dvyukov@google.com> wrote:
> > > > >
> > > > > > +void kasan_init(void)
> > > > > > +{
> > > > > > +       kasan_map_memory((void *)KASAN_SHADOW_START, KASAN_SHADOW_SIZE);
> > > > > > +
> > > > > > +       // unpoison the kernel text which is form uml_physmem -> uml_reserved
> > > > > > +       kasan_unpoison_shadow((void *)uml_physmem, physmem_size);
> > > > > > +
> > > > > > +       // unpoison the vmalloc region, which is start_vm -> end_vm
> > > > > > +       kasan_unpoison_shadow((void *)start_vm, (end_vm - start_vm + 1));
> > > > > > +
> > > > > > +       init_task.kasan_depth = 0;
> > > > > > +       pr_info("KernelAddressSanitizer initialized\n");
> > > > > > +}
> > > > >
> > > > > Was this tested with stack instrumentation? Stack instrumentation
> > > > > changes what shadow is being read/written and when. We don't need to
> > > > > get it working right now, but if it does not work it would be nice to
> > > > > restrict the setting and leave some comment traces for future
> > > > > generations.
> > > > If you are referring to KASAN_STACK_ENABLE, I just tested it and it
> > > > seems to work fine.
> > >
> > >
> > > I mean stack instrumentation which is enabled with CONFIG_KASAN_STACK.
> >
> > I believe I was testing with CONFIG_KASAN_STACK set to 1 since that is
> > the default value when compiling with GCC.The syscall_stub_data error
> > disappears when the value of CONFIG_KASAN_STACK is 0, though.
>
>
> Then I would either disable it for now for UML, or try to unpoision
> stack or ignore accesses.
>
Okay, I'll probably disable it in UML for now.


-- 
Patricia Alfonso