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From:   Marco Elver <elver@google.com>
Date:   Mon, 17 Oct 2022 18:00:00 -0700
Message-ID: <CANpmjNM3KrZGbmP2J3o_QNv6QquejA0fQN62mx-biYnEY4xF+g@mail.gmail.com>
Subject: Re: [PATCH AUTOSEL 6.0 22/32] kmsan: disable instrumentation of
 unsupported common kernel code
To:     Sasha Levin <sashal@kernel.org>
Cc:     linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Alexander Potapenko <glider@google.com>
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[-Cc prune most]

Does this mean KMSAN is being backported to stable? I only see a
subset of patches.

On Mon, 17 Oct 2022 at 17:08, Sasha Levin <sashal@kernel.org> wrote:
>
> From: Alexander Potapenko <glider@google.com>
>
> [ Upstream commit 79dbd006a6d6f51777ba4948046561b6d9270504 ]
>
> EFI stub cannot be linked with KMSAN runtime, so we disable
> instrumentation for it.
>
> Instrumenting kcov, stackdepot or lockdep leads to infinite recursion
> caused by instrumentation hooks calling instrumented code again.
>
> Link: https://lkml.kernel.org/r/20220915150417.722975-13-glider@google.com
> Signed-off-by: Alexander Potapenko <glider@google.com>
> Reviewed-by: Marco Elver <elver@google.com>
> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Andrey Konovalov <andreyknvl@gmail.com>
> Cc: Andrey Konovalov <andreyknvl@google.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Eric Biggers <ebiggers@google.com>
> Cc: Eric Biggers <ebiggers@kernel.org>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Herbert Xu <herbert@gondor.apana.org.au>
> Cc: Ilya Leoshkevich <iii@linux.ibm.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Petr Mladek <pmladek@suse.com>
> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Vasily Gorbik <gor@linux.ibm.com>
> Cc: Vegard Nossum <vegard.nossum@oracle.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  drivers/firmware/efi/libstub/Makefile | 1 +
>  kernel/Makefile                       | 1 +
>  kernel/locking/Makefile               | 3 ++-
>  lib/Makefile                          | 3 +++
>  4 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index 2c67f71f2375..2c1eb1fb0f22 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -53,6 +53,7 @@ GCOV_PROFILE                  := n
>  # Sanitizer runtimes are unavailable and cannot be linked here.
>  KASAN_SANITIZE                 := n
>  KCSAN_SANITIZE                 := n
> +KMSAN_SANITIZE                 := n
>  UBSAN_SANITIZE                 := n
>  OBJECT_FILES_NON_STANDARD      := y
>
> diff --git a/kernel/Makefile b/kernel/Makefile
> index 318789c728d3..d754e0be1176 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -38,6 +38,7 @@ KCOV_INSTRUMENT_kcov.o := n
>  KASAN_SANITIZE_kcov.o := n
>  KCSAN_SANITIZE_kcov.o := n
>  UBSAN_SANITIZE_kcov.o := n
> +KMSAN_SANITIZE_kcov.o := n
>  CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack) -fno-stack-protector
>
>  # Don't instrument error handlers
> diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
> index d51cabf28f38..ea925731fa40 100644
> --- a/kernel/locking/Makefile
> +++ b/kernel/locking/Makefile
> @@ -5,8 +5,9 @@ KCOV_INSTRUMENT         := n
>
>  obj-y += mutex.o semaphore.o rwsem.o percpu-rwsem.o
>
> -# Avoid recursion lockdep -> KCSAN -> ... -> lockdep.
> +# Avoid recursion lockdep -> sanitizer -> ... -> lockdep.
>  KCSAN_SANITIZE_lockdep.o := n
> +KMSAN_SANITIZE_lockdep.o := n
>
>  ifdef CONFIG_FUNCTION_TRACER
>  CFLAGS_REMOVE_lockdep.o = $(CC_FLAGS_FTRACE)
> diff --git a/lib/Makefile b/lib/Makefile
> index ffabc30a27d4..fcebece0f5b6 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -275,6 +275,9 @@ obj-$(CONFIG_POLYNOMIAL) += polynomial.o
>  CFLAGS_stackdepot.o += -fno-builtin
>  obj-$(CONFIG_STACKDEPOT) += stackdepot.o
>  KASAN_SANITIZE_stackdepot.o := n
> +# In particular, instrumenting stackdepot.c with KMSAN will result in infinite
> +# recursion.
> +KMSAN_SANITIZE_stackdepot.o := n
>  KCOV_INSTRUMENT_stackdepot.o := n
>
>  obj-$(CONFIG_REF_TRACKER) += ref_tracker.o
> --
> 2.35.1
>