linux-kernel - Re: [PATCH 14/17] arm64: add __nocfi to functions that jump to a physical address

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Message-ID: <202103111847.0EC7EDBF@keescook>
Date:   Thu, 11 Mar 2021 18:47:52 -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 14/17] arm64: add __nocfi to functions that jump to a
 physical address

On Thu, Mar 11, 2021 at 04:49:16PM -0800, Sami Tolvanen wrote:
> Disable CFI checking for functions that switch to linear mapping and
> make an indirect call to a physical address, since the compiler only
> understands virtual addresses and the CFI check for such indirect calls
> would always fail.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>

(I wonder if there is some value in a separate macro for "makes a PA
call"? Might other things care about that besides just CFI?)

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

-- 
Kees Cook