Re: [PATCH v3] kasan: remove redundant config option

[Nathan Chancellor <natechancellor@gmail.com>]

On Mon, Jan 11, 2021 at 06:49:37PM +0100, Andrey Konovalov wrote:
> On Fri, Jan 8, 2021 at 5:09 AM Walter Wu <walter-zh.wu@mediatek.com> wrote:
> >
> > CONFIG_KASAN_STACK and CONFIG_KASAN_STACK_ENABLE both enable KASAN stack
> > instrumentation, but we should only need one config, so that we remove
> > CONFIG_KASAN_STACK_ENABLE and make CONFIG_KASAN_STACK workable. see [1].
> >
> > When enable KASAN stack instrumentation, then for gcc we could do
> > no prompt and default value y, and for clang prompt and default
> > value n.
> >
> > [1]: https://bugzilla.kernel.org/show_bug.cgi?id=210221
> >
> > Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
> > Suggested-by: Dmitry Vyukov <dvyukov@google.com>
> > Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
> > Cc: Dmitry Vyukov <dvyukov@google.com>
> > Cc: Andrey Konovalov <andreyknvl@google.com>
> > Cc: Alexander Potapenko <glider@google.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Nathan Chancellor <natechancellor@gmail.com>
> > ---
> >
> > v2: make commit log to be more readable.
> > v3: remain CONFIG_KASAN_STACK_ENABLE setting
> >     fix the pre-processors syntax
> >
> > ---
> >  arch/arm64/kernel/sleep.S        |  2 +-
> >  arch/x86/kernel/acpi/wakeup_64.S |  2 +-
> >  include/linux/kasan.h            |  2 +-
> >  lib/Kconfig.kasan                |  8 ++------
> >  mm/kasan/common.c                |  2 +-
> >  mm/kasan/kasan.h                 |  2 +-
> >  mm/kasan/report_generic.c        |  2 +-
> >  scripts/Makefile.kasan           | 10 ++++++++--
> >  8 files changed, 16 insertions(+), 14 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
> > index 6bdef7362c0e..7c44ede122a9 100644
> > --- a/arch/arm64/kernel/sleep.S
> > +++ b/arch/arm64/kernel/sleep.S
> > @@ -133,7 +133,7 @@ SYM_FUNC_START(_cpu_resume)
> >          */
> >         bl      cpu_do_resume
> >
> > -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> > +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> >         mov     x0, sp
> >         bl      kasan_unpoison_task_stack_below
> >  #endif
> > diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
> > index 5d3a0b8fd379..c7f412f4e07d 100644
> > --- a/arch/x86/kernel/acpi/wakeup_64.S
> > +++ b/arch/x86/kernel/acpi/wakeup_64.S
> > @@ -112,7 +112,7 @@ SYM_FUNC_START(do_suspend_lowlevel)
> >         movq    pt_regs_r14(%rax), %r14
> >         movq    pt_regs_r15(%rax), %r15
> >
> > -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> > +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> >         /*
> >          * The suspend path may have poisoned some areas deeper in the stack,
> >          * which we now need to unpoison.
> > diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> > index 5e0655fb2a6f..35d1e9b2cbfa 100644
> > --- a/include/linux/kasan.h
> > +++ b/include/linux/kasan.h
> > @@ -302,7 +302,7 @@ static inline void kasan_kfree_large(void *ptr, unsigned long ip) {}
> >
> >  #endif /* CONFIG_KASAN */
> >
> > -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> > +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> >  void kasan_unpoison_task_stack(struct task_struct *task);
> >  #else
> >  static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
> > diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> > index f5fa4ba126bf..fde82ec85f8f 100644
> > --- a/lib/Kconfig.kasan
> > +++ b/lib/Kconfig.kasan
> > @@ -138,9 +138,10 @@ config KASAN_INLINE
> >
> >  endchoice
> >
> > -config KASAN_STACK_ENABLE
> > +config KASAN_STACK
> >         bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
> 
> Does this syntax mean that KASAN_STACK is only present for
> CC_IS_CLANG? Or that it can only be disabled for CC_IS_CLANG?

It means that the option can only be disabled for clang.

> Anyway, I think it's better to 1. allow to control KASAN_STACK
> regardless of the compiler (as it was possible before), and 2. avoid

It has never been possible to control KASAN_STACK for GCC because of the
bool ... if ... syntax. This patch does not change that logic. Making it
possible to control KASAN_STACK with GCC seems fine but that is going to
be a new change that would probably be suited for a new patch on top of
this one.

> this "bool ... if ..." syntax as it's confusing.
> 
> >         depends on KASAN_GENERIC || KASAN_SW_TAGS
> > +       default y if CC_IS_GCC
> >         help
> >           The LLVM stack address sanitizer has a know problem that
> >           causes excessive stack usage in a lot of functions, see
> > @@ -154,11 +155,6 @@ config KASAN_STACK_ENABLE
> >           CONFIG_COMPILE_TEST.  On gcc it is assumed to always be safe
> >           to use and enabled by default.
> >
> > -config KASAN_STACK
> > -       int
> > -       default 1 if KASAN_STACK_ENABLE || CC_IS_GCC
> > -       default 0
> > -
> >  config KASAN_SW_TAGS_IDENTIFY
> >         bool "Enable memory corruption identification"
> >         depends on KASAN_SW_TAGS
> > diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> > index 38ba2aecd8f4..bf8b073eed62 100644
> > --- a/mm/kasan/common.c
> > +++ b/mm/kasan/common.c
> > @@ -63,7 +63,7 @@ void __kasan_unpoison_range(const void *address, size_t size)
> >         unpoison_range(address, size);
> >  }
> >
> > -#if CONFIG_KASAN_STACK
> > +#ifdef CONFIG_KASAN_STACK
> >  /* Unpoison the entire stack for a task. */
> >  void kasan_unpoison_task_stack(struct task_struct *task)
> >  {
> > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> > index cc4d9e1d49b1..bdfdb1cff653 100644
> > --- a/mm/kasan/kasan.h
> > +++ b/mm/kasan/kasan.h
> > @@ -224,7 +224,7 @@ void *find_first_bad_addr(void *addr, size_t size);
> >  const char *get_bug_type(struct kasan_access_info *info);
> >  void metadata_fetch_row(char *buffer, void *row);
> >
> > -#if defined(CONFIG_KASAN_GENERIC) && CONFIG_KASAN_STACK
> > +#if defined(CONFIG_KASAN_GENERIC) && defined(CONFIG_KASAN_STACK)
> >  void print_address_stack_frame(const void *addr);
> >  #else
> >  static inline void print_address_stack_frame(const void *addr) { }
> > diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c
> > index 8a9c889872da..4e16518d9877 100644
> > --- a/mm/kasan/report_generic.c
> > +++ b/mm/kasan/report_generic.c
> > @@ -128,7 +128,7 @@ void metadata_fetch_row(char *buffer, void *row)
> >         memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
> >  }
> >
> > -#if CONFIG_KASAN_STACK
> > +#ifdef CONFIG_KASAN_STACK
> >  static bool __must_check tokenize_frame_descr(const char **frame_descr,
> >                                               char *token, size_t max_tok_len,
> >                                               unsigned long *value)
> > diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> > index 1e000cc2e7b4..abf231d209b1 100644
> > --- a/scripts/Makefile.kasan
> > +++ b/scripts/Makefile.kasan
> > @@ -2,6 +2,12 @@
> >  CFLAGS_KASAN_NOSANITIZE := -fno-builtin
> >  KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
> >
> > +ifdef CONFIG_KASAN_STACK
> > +       stack_enable := 1
> > +else
> > +       stack_enable := 0
> > +endif
> > +
> >  ifdef CONFIG_KASAN_GENERIC
> >
> >  ifdef CONFIG_KASAN_INLINE
> > @@ -27,7 +33,7 @@ else
> >         CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
> >          $(call cc-param,asan-globals=1) \
> >          $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
> > -        $(call cc-param,asan-stack=$(CONFIG_KASAN_STACK)) \
> > +        $(call cc-param,asan-stack=$(stack_enable)) \
> >          $(call cc-param,asan-instrument-allocas=1)
> >  endif
> >
> > @@ -42,7 +48,7 @@ else
> >  endif
> >
> >  CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
> > -               -mllvm -hwasan-instrument-stack=$(CONFIG_KASAN_STACK) \
> > +               -mllvm -hwasan-instrument-stack=$(stack_enable) \
> >                 -mllvm -hwasan-use-short-granules=0 \
> >                 $(instrumentation_flags)
> >
> > --
> > 2.18.0
> >
> > --
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