linux-hardening - Re: [PATCH 15/17] arm64: add __nocfi to __apply

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Message-ID: <202103111850.4C29C4C47@keescook>
Date:   Thu, 11 Mar 2021 18:50:31 -0800
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>,
        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 15/17] arm64: add __nocfi to __apply_alternatives

On Thu, Mar 11, 2021 at 04:49:17PM -0800, Sami Tolvanen wrote:
> __apply_alternatives makes indirect calls to functions whose address
> is taken in assembly code using the alternative_cb macro. With
> non-canonical CFI, the compiler won't replace these function
> references with the jump table addresses, which trips CFI. Disable CFI
> checking in the function to work around the issue.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>

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

-- 
Kees Cook