linux-kernel - Re: [PATCH 2/3] kbuild: clamp SUBLEVEL to 255

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Date:   Sun, 7 Feb 2021 11:52:43 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     Michal Marek <michal.lkml@...kovi.net>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 2/3] kbuild: clamp SUBLEVEL to 255

On Sat, Feb 6, 2021 at 12:50 PM Sasha Levin <sashal@...nel.org> wrote:
>
> Right now if SUBLEVEL becomes larger than 255 it will overflow into the
> territory of PATCHLEVEL, causing havoc in userspace that tests for
> specific kernel version.
>
> While userspace code tests for MAJOR and PATCHLEVEL, it doesn't test
> SUBLEVEL at any point as ABI changes don't happen in the context of
> stable tree.
>
> Thus, to avoid overflows, simply clamp SUBLEVEL to it's maximum value in
> the context of LINUX_VERSION_CODE. This does not affect "make
> kernelversion" and such.
>
> Signed-off-by: Sasha Levin <sashal@...nel.org>


I applied 2/3 to linux-kbuild.

Please resend only 3/3.

Thanks.



> ---
>  Makefile | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 49ac1b7fe8e99..157be50c691e5 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1258,9 +1258,15 @@ define filechk_utsrelease.h
>  endef
>
>  define filechk_version.h
> -       echo \#define LINUX_VERSION_CODE $(shell                         \
> -       expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \
> -       echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
> +       if [ $(SUBLEVEL) -gt 255 ]; then                                 \
> +               echo \#define LINUX_VERSION_CODE $(shell                 \
> +               expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 255); \
> +       else                                                             \
> +               echo \#define LINUX_VERSION_CODE $(shell                 \
> +               expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \
> +       fi;                                                              \
> +       echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) +  \
> +       ((c) > 255 ? 255 : (c)))'
>  endef
>
>  $(version_h): FORCE
> --
> 2.27.0
>


-- 
Best Regards
Masahiro Yamada