Kernel-hardening archive on lore.kernel.org
 help / color / Atom feed
From: Kees Cook <keescook@chromium.org>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Elena Petrova <lenaptr@google.com>,
	Alexander Potapenko <glider@google.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	kasan-dev <kasan-dev@googlegroups.com>,
	LKML <linux-kernel@vger.kernel.org>,
	kernel-hardening@lists.openwall.com,
	syzkaller <syzkaller@googlegroups.com>
Subject: Re: [PATCH v2 0/3] ubsan: Split out bounds checker
Date: Wed, 27 Nov 2019 09:59:18 -0800
Message-ID: <201911270952.D66CD15AEC@keescook> (raw)
In-Reply-To: <CACT4Y+aFiwxT6SO-ABx695Yg3=Zam5saqCo4+FembPwKSV8cug@mail.gmail.com>

On Wed, Nov 27, 2019 at 10:34:24AM +0100, Dmitry Vyukov wrote:
> On Wed, Nov 27, 2019 at 7:54 AM Dmitry Vyukov <dvyukov@google.com> wrote:
> >
> > On Wed, Nov 27, 2019 at 6:42 AM Kees Cook <keescook@chromium.org> wrote:
> > >
> > > On Fri, Nov 22, 2019 at 10:07:29AM +0100, Dmitry Vyukov wrote:
> > > > On Thu, Nov 21, 2019 at 7:15 PM Kees Cook <keescook@chromium.org> wrote:
> > > > >
> > > > > v2:
> > > > >     - clarify Kconfig help text (aryabinin)
> > > > >     - add reviewed-by
> > > > >     - aim series at akpm, which seems to be where ubsan goes through?
> > > > > v1: https://lore.kernel.org/lkml/20191120010636.27368-1-keescook@chromium.org
> > > > >
> > > > > This splits out the bounds checker so it can be individually used. This
> > > > > is expected to be enabled in Android and hopefully for syzbot. Includes
> > > > > LKDTM tests for behavioral corner-cases (beyond just the bounds checker).
> > > > >
> > > > > -Kees
> > > >
> > > > +syzkaller mailing list
> > > >
> > > > This is great!
> > >
> > > BTW, can I consider this your Acked-by for these patches? :)
> > >
> > > > I wanted to enable UBSAN on syzbot for a long time. And it's
> > > > _probably_ not lots of work. But it was stuck on somebody actually
> > > > dedicating some time specifically for it.
> > >
> > > Do you have a general mechanism to test that syzkaller will actually
> > > pick up the kernel log splat of a new check?
> >
> > Yes. That's one of the most important and critical parts of syzkaller :)
> > The tests for different types of bugs are here:
> > https://github.com/google/syzkaller/tree/master/pkg/report/testdata/linux/report
> >
> > But have 3 for UBSAN, but they may be old and it would be useful to
> > have 1 example crash per bug type:
> >
> > syzkaller$ grep UBSAN pkg/report/testdata/linux/report/*
> > pkg/report/testdata/linux/report/40:TITLE: UBSAN: Undefined behaviour
> > in drivers/usb/core/devio.c:LINE
> > pkg/report/testdata/linux/report/40:[    4.556972] UBSAN: Undefined
> > behaviour in drivers/usb/core/devio.c:1517:25
> > pkg/report/testdata/linux/report/41:TITLE: UBSAN: Undefined behaviour
> > in ./arch/x86/include/asm/atomic.h:LINE
> > pkg/report/testdata/linux/report/41:[    3.805453] UBSAN: Undefined
> > behaviour in ./arch/x86/include/asm/atomic.h:156:2
> > pkg/report/testdata/linux/report/42:TITLE: UBSAN: Undefined behaviour
> > in kernel/time/hrtimer.c:LINE
> > pkg/report/testdata/linux/report/42:[   50.583499] UBSAN: Undefined
> > behaviour in kernel/time/hrtimer.c:310:16
> >
> > One of them is incomplete and is parsed as "corrupted kernel output"
> > (won't be reported):
> > https://github.com/google/syzkaller/blob/master/pkg/report/testdata/linux/report/42
> >
> > Also I see that report parsing just takes the first line, which
> > includes file name, which is suboptimal (too long, can't report 2 bugs
> > in the same file). We seem to converge on "bug-type in function-name"
> > format.
> > The thing about bug titles is that it's harder to change them later.
> > If syzbot already reported 100 bugs and we change titles, it will
> > start re-reporting the old one after new names and the old ones will
> > look stale, yet they still relevant, just detected under different
> > name.
> > So we also need to get this part right before enabling.

It Sounds like instead of "UBSAN: Undefined behaviour in $file", UBSAN
should report something like "UBSAN: $behavior in $file"?

e.g.
40: UBSAN: bad shift in drivers/usb/core/devio.c:1517:25"
41: UBSAN: signed integer overflow in ./arch/x86/include/asm/atomic.h:156:2

I'll add one for the bounds checker.

How are these reports used? (And is there a way to check a live kernel
crash? i.e. to tell syzkaller "echo ARRAY_BOUNDS >/.../lkdtm..." and
generate a report?

> > > I noticed a few things
> > > about the ubsan handlers: they don't use any of the common "warn"
> > > infrastructure (neither does kasan from what I can see), and was missing
> > > a check for panic_on_warn (kasan has this, but does it incorrectly).
> >
> > Yes, panic_on_warn we also need.
> >
> > I will look at the patches again for Acked-by.
> 
> 
> Acked-by: Dmitry Vyukov <dvyukov@google.com>
> for the series.

Thanks!

> 
> I see you extended the test module, do you have samples of all UBSAN
> report types that are triggered by these functions? Is so, please add
> them to:
> https://github.com/google/syzkaller/tree/master/pkg/report/testdata/linux/report

Okay, cool.

> with whatever titles they are detected now. Improving titles will then
> be the next step, but much simpler with a good collection of tests.
> 
> Will you send the panic_on_want patch as well?

Yes; I wanted to make sure it was needed first (which you've confirmed
now). I'll likely not send it until next week.

-- 
Kees Cook

  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-21 18:15 Kees Cook
2019-11-21 18:15 ` [PATCH v2 1/3] ubsan: Add trap instrumentation option Kees Cook
2019-12-16 10:26   ` Will Deacon
2019-12-18  0:08     ` Kees Cook
2019-11-21 18:15 ` [PATCH v2 2/3] ubsan: Split "bounds" checker from other options Kees Cook
2019-11-21 18:15 ` [PATCH v2 3/3] lkdtm/bugs: Add arithmetic overflow and array bounds checks Kees Cook
2019-11-22  9:07 ` [PATCH v2 0/3] ubsan: Split out bounds checker Dmitry Vyukov
2019-11-22 16:52   ` Kees Cook
2019-11-27  5:42   ` Kees Cook
2019-11-27  6:54     ` Dmitry Vyukov
2019-11-27  9:34       ` Dmitry Vyukov
2019-11-27 17:59         ` Kees Cook [this message]
2019-11-28 10:38           ` Dmitry Vyukov
2019-11-28 16:14             ` Qian Cai
2019-11-28 13:10           ` Dmitry Vyukov

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=201911270952.D66CD15AEC@keescook \
    --to=keescook@chromium.org \
    --cc=akpm@linux-foundation.org \
    --cc=ard.biesheuvel@linaro.org \
    --cc=arnd@arndb.de \
    --cc=aryabinin@virtuozzo.com \
    --cc=dan.carpenter@oracle.com \
    --cc=dvyukov@google.com \
    --cc=glider@google.com \
    --cc=gustavo@embeddedor.com \
    --cc=kasan-dev@googlegroups.com \
    --cc=kernel-hardening@lists.openwall.com \
    --cc=lenaptr@google.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=syzkaller@googlegroups.com \
    --cc=torvalds@linux-foundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Kernel-hardening archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kernel-hardening/0 kernel-hardening/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kernel-hardening kernel-hardening/ https://lore.kernel.org/kernel-hardening \
		kernel-hardening@lists.openwall.com
	public-inbox-index kernel-hardening

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/com.openwall.lists.kernel-hardening


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git