linux-kernel - Re: [PATCH v3 04/17] module: ensure __cfi

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Message-ID: <202103252133.339A7A49@keescook>
Date:   Thu, 25 Mar 2021 21:34:03 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Will Deacon <will@...nel.org>, Jessica Yu <jeyu@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Tejun Heo <tj@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>, bpf@...r.kernel.org,
        linux-hardening@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 04/17] module: ensure __cfi_check alignment

On Tue, Mar 23, 2021 at 01:39:33PM -0700, Sami Tolvanen wrote:
> CONFIG_CFI_CLANG_SHADOW assumes the __cfi_check() function is page
> aligned and at the beginning of the .text section. While Clang would
> normally align the function correctly, it fails to do so for modules
> with no executable code.
> 
> This change ensures the correct __cfi_check() location and
> alignment. It also discards the .eh_frame section, which Clang can
> generate with certain sanitizers, such as CFI.
> 
> Link: https://bugs.llvm.org/show_bug.cgi?id=46293
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>

Yay macros! :)

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

-- 
Kees Cook