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Date: Thu, 21 Nov 2019 09:20:55 -0800
From: Kees Cook <keescook@...omium.org>
To: Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc: Elena Petrova <lenaptr@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Dan Carpenter <dan.carpenter@...cle.com>,
"Gustavo A. R. Silva" <gustavo@...eddedor.com>,
Arnd Bergmann <arnd@...db.de>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Andrew Morton <akpm@...ux-foundation.org>,
kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH 1/3] ubsan: Add trap instrumentation option
On Thu, Nov 21, 2019 at 03:52:52PM +0300, Andrey Ryabinin wrote:
> On 11/20/19 4:06 AM, Kees Cook wrote:
>
>
> > +config UBSAN_TRAP
> > + bool "On Sanitizer warnings, stop the offending kernel thread"
>
> That description seems inaccurate and confusing. It's not about kernel threads.
> UBSAN may trigger in any context - kernel thread/user process/interrupts...
> Probably most of the kernel code runs in the context of user process, so "stop the offending kernel thread"
> doesn't sound right.
>
>
>
> > + depends on UBSAN
> > + depends on $(cc-option, -fsanitize-undefined-trap-on-error)
> > + help
> > + Building kernels with Sanitizer features enabled tends to grow
> > + the kernel size by over 5%, due to adding all the debugging
> > + text on failure paths. To avoid this, Sanitizer instrumentation
> > + can just issue a trap. This reduces the kernel size overhead but
> > + turns all warnings into full thread-killing exceptions.
>
> I think we should mention that enabling this option also has a potential to
> turn some otherwise harmless bugs into more severe problems like lockups, kernel panic etc..
> So the people who enable this would better understand what they signing up for.
Good point about other contexts. I will attempt to clarify and send a
v2.
BTW, which tree should ubsan changes go through? The files are actually
not mentioned by anything in MAINTAINERS. Should the KASAN entry gain
paths to cover ubsan too? Something like:
diff --git a/MAINTAINERS b/MAINTAINERS
index 9dffd64d5e99..585434c013c4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8824,7 +8824,7 @@ S: Maintained
F: Documentation/hwmon/k8temp.rst
F: drivers/hwmon/k8temp.c
-KASAN
+KERNEL SANITIZERS (KASAN, UBSAN)
M: Andrey Ryabinin <aryabinin@...tuozzo.com>
R: Alexander Potapenko <glider@...gle.com>
R: Dmitry Vyukov <dvyukov@...gle.com>
@@ -8834,9 +8834,13 @@ F: arch/*/include/asm/kasan.h
F: arch/*/mm/kasan_init*
F: Documentation/dev-tools/kasan.rst
F: include/linux/kasan*.h
+F: lib/Kconfig.ubsan
F: lib/test_kasan.c
+F: lib/test_ubsan.c
+F: lib/ubsan.c
F: mm/kasan/
F: scripts/Makefile.kasan
+F: scripts/Makefile.ubsan
KCONFIG
M: Masahiro Yamada <yamada.masahiro@...ionext.com>
--
Kees Cook
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