[PATCH] [v2] kasan: remove clang version check for KASAN_STACK

[PATCH] [v2] kasan: remove clang version check for KASAN_STACK

[Arnd Bergmann]

asan-stack mode still uses dangerously large kernel stacks of
tens of kilobytes in some drivers, and it does not seem that anyone
is working on the clang bug.

Turn it off for all clang versions to prevent users from
accidentally enabling it once they update to clang-9, and
to help automated build testing with clang-9.

Link: https://bugs.llvm.org/show_bug.cgi?id=38809
Fixes: 6baec880d7a5 ("kasan: turn off asan-stack for clang-8 and earlier")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
v2: disable the feature for all clang versions, not just 9 and below.
---
 lib/Kconfig.kasan | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 4fafba1a923b..7fa97a8b5717 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -106,7 +106,6 @@ endchoice
 
 config KASAN_STACK_ENABLE
 	bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
-	default !(CLANG_VERSION < 90000)
 	depends on KASAN
 	help
 	  The LLVM stack address sanitizer has a know problem that
@@ -115,11 +114,11 @@ config KASAN_STACK_ENABLE
 	  Disabling asan-stack makes it safe to run kernels build
 	  with clang-8 with KASAN enabled, though it loses some of
 	  the functionality.
-	  This feature is always disabled when compile-testing with clang-8
-	  or earlier to avoid cluttering the output in stack overflow
-	  warnings, but clang-8 users can still enable it for builds without
-	  CONFIG_COMPILE_TEST.  On gcc and later clang versions it is
-	  assumed to always be safe to use and enabled by default.
+	  This feature is always disabled when compile-testing with clang
+	  to avoid cluttering the output in stack overflow warnings,
+	  but clang users can still enable it for builds without
+	  CONFIG_COMPILE_TEST.	On gcc it is assumed to always be safe
+	  to use and enabled by default.
 
 config KASAN_STACK
 	int
-- 
2.20.0

Re: [PATCH] [v2] kasan: remove clang version check for KASAN_STACK

[Nick Desaulniers]

On Fri, Jul 19, 2019 at 1:03 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> asan-stack mode still uses dangerously large kernel stacks of
> tens of kilobytes in some drivers, and it does not seem that anyone
> is working on the clang bug.

Acked-by: Nick Desaulniers <ndesaulniers@google.com>

>
> Turn it off for all clang versions to prevent users from
> accidentally enabling it once they update to clang-9, and
> to help automated build testing with clang-9.
>
> Link: https://bugs.llvm.org/show_bug.cgi?id=38809
> Fixes: 6baec880d7a5 ("kasan: turn off asan-stack for clang-8 and earlier")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> v2: disable the feature for all clang versions, not just 9 and below.
> ---
>  lib/Kconfig.kasan | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index 4fafba1a923b..7fa97a8b5717 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -106,7 +106,6 @@ endchoice
>
>  config KASAN_STACK_ENABLE
>         bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
> -       default !(CLANG_VERSION < 90000)
>         depends on KASAN
>         help
>           The LLVM stack address sanitizer has a know problem that
> @@ -115,11 +114,11 @@ config KASAN_STACK_ENABLE
>           Disabling asan-stack makes it safe to run kernels build
>           with clang-8 with KASAN enabled, though it loses some of
>           the functionality.
> -         This feature is always disabled when compile-testing with clang-8
> -         or earlier to avoid cluttering the output in stack overflow
> -         warnings, but clang-8 users can still enable it for builds without
> -         CONFIG_COMPILE_TEST.  On gcc and later clang versions it is
> -         assumed to always be safe to use and enabled by default.
> +         This feature is always disabled when compile-testing with clang
> +         to avoid cluttering the output in stack overflow warnings,
> +         but clang users can still enable it for builds without
> +         CONFIG_COMPILE_TEST.  On gcc it is assumed to always be safe
> +         to use and enabled by default.
>
>  config KASAN_STACK
>         int
> --
> 2.20.0
>
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-- 
Thanks,
~Nick Desaulniers

Re: [PATCH] [v2] kasan: remove clang version check for KASAN_STACK

[Andrey Ryabinin]

On 7/19/19 11:03 PM, Arnd Bergmann wrote:
> asan-stack mode still uses dangerously large kernel stacks of
> tens of kilobytes in some drivers, and it does not seem that anyone
> is working on the clang bug.
> 
> Turn it off for all clang versions to prevent users from
> accidentally enabling it once they update to clang-9, and
> to help automated build testing with clang-9.
> 
> Link: https://bugs.llvm.org/show_bug.cgi?id=38809
> Fixes: 6baec880d7a5 ("kasan: turn off asan-stack for clang-8 and earlier")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>

Re: [PATCH] [v2] kasan: remove clang version check for KASAN_STACK

[Mark Brown]

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On Fri, Jul 19, 2019 at 10:03:31PM +0200, Arnd Bergmann wrote:
> asan-stack mode still uses dangerously large kernel stacks of
> tens of kilobytes in some drivers, and it does not seem that anyone
> is working on the clang bug.

Reviewed-by: Mark Brown <broonie@kernel.org>

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