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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