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From: Kees Cook <keescook@chromium.org>
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: linux-kbuild@vger.kernel.org,
	Sami Tolvanen <samitolvanen@google.com>,
	linux-kernel@vger.kernel.org,
	Michal Marek <michal.lkml@markovi.net>,
	Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: [PATCH 05/13] kbuild: remove stale *.symversions
Date: Wed, 18 Aug 2021 23:29:10 -0700	[thread overview]
Message-ID: <202108182328.5CF89AC2@keescook> (raw)
In-Reply-To: <20210819005744.644908-6-masahiroy@kernel.org>

On Thu, Aug 19, 2021 at 09:57:36AM +0900, Masahiro Yamada wrote:
> cmd_update_lto_symversions merges all the existing *.symversions, but
> some of them might be stale.
> 
> If the last EXPORT_SYMBOL is removed from a C file, the *.symversions
> file is not deleted or updated. It contains stale CRCs, which will be
> used for linking the vmlinux or modules.
> 
> It is not a big deal when the EXPORT_SYMBOL is really removed. However,
> when the EXPORT_SYMBOL is moved to another file, the same __crc_<symbol>
> will appear twice in the merged *.symversions, possibly with different
> CRCs if the function argument is changed at the same time. It would
> cause potential breakage of module versioning.
> 
> If no EXPORT_SYMBOL is found, let's remove *.symversions explicitly.

Ah, and this was an issue for non-LTO builds too? Regardless, nice
catch.

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
> 
>  scripts/Makefile.build | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 279363266455..585dae34746a 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -177,6 +177,8 @@ cmd_modversions_c =								\
>  	if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then			\
>  		$(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
>  		    > $@.symversions;						\
> +	else									\
> +		rm -f $@.symversions;						\
>  	fi;
>  else
>  cmd_modversions_c =								\
> -- 
> 2.30.2
> 

-- 
Kees Cook

  reply	other threads:[~2021-08-19  6:29 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-19  0:57 [PATCH 00/13] kbuild: refactoring after Clang LTO Masahiro Yamada
2021-08-19  0:57 ` [PATCH 01/13] kbuild: move objtool_args back to scripts/Makefile.build Masahiro Yamada
2021-08-19  2:45   ` Kees Cook
2021-08-19  0:57 ` [PATCH 02/13] gen_compile_commands: extract compiler command from a series of commands Masahiro Yamada
2021-08-19  6:48   ` Kees Cook
2021-08-19  0:57 ` [PATCH 03/13] kbuild: detect objtool changes correctly and remove .SECONDEXPANSION Masahiro Yamada
2021-08-19  2:55   ` Kees Cook
2021-08-19  3:18     ` Masahiro Yamada
2021-08-19  0:57 ` [PATCH 04/13] kbuild: remove unused quiet_cmd_update_lto_symversions Masahiro Yamada
2021-08-19  6:19   ` Kees Cook
2021-08-19  0:57 ` [PATCH 05/13] kbuild: remove stale *.symversions Masahiro Yamada
2021-08-19  6:29   ` Kees Cook [this message]
2021-08-19  0:57 ` [PATCH 06/13] kbuild: merge vmlinux_link() between the ordinary link and Clang LTO Masahiro Yamada
2021-08-19  2:42   ` Kees Cook
2021-08-19  0:57 ` [PATCH 07/13] kbuild: do not remove 'linux' link in scripts/link-vmlinux.sh Masahiro Yamada
2021-08-19  6:32   ` Kees Cook
2021-08-19  0:57 ` [PATCH 08/13] kbuild: merge vmlinux_link() between ARCH=um and other architectures Masahiro Yamada
2021-08-19  2:43   ` Kees Cook
2021-08-19  0:57 ` [PATCH 09/13] kbuild: do not create built-in.a.symversions or lib.a.symversions Masahiro Yamada
2021-08-19  6:41   ` Kees Cook
2021-08-28 11:57     ` Masahiro Yamada
2021-08-19  0:57 ` [PATCH 10/13] kbuild: build modules in the same way with/without Clang LTO Masahiro Yamada
2021-08-19  6:59   ` Kees Cook
2021-08-19  8:11     ` Masahiro Yamada
2021-08-19  0:57 ` [PATCH 11/13] kbuild: always postpone CRC links for module versioning Masahiro Yamada
2021-08-19  6:43   ` Kees Cook
2021-08-19  0:57 ` [PATCH 12/13] kbuild: merge cmd_modversions_c and cmd_modversions_S Masahiro Yamada
2021-08-19  3:06   ` Kees Cook
2021-08-19  0:57 ` [PATCH 13/13] kbuild: merge cmd_ar_builtin and cmd_ar_module Masahiro Yamada
2021-08-19  3:01   ` Kees Cook
2021-08-25  4:57 ` [PATCH 00/13] kbuild: refactoring after Clang LTO Masahiro Yamada

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