linux-hardening - Re: [PATCH 07/17] kallsyms: cfi: strip hashes from static functions

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Message-ID: <CABCJKufMb_VFwXLkxjdvN6Y92v-Nc4Z+kThbi7SOkVgGhdFz+g@mail.gmail.com>
Date:   Tue, 16 Mar 2021 13:33:53 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Kees Cook <keescook@...omium.org>
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 <linux-arch@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kbuild <linux-kbuild@...r.kernel.org>,
        PCI <linux-pci@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/17] kallsyms: cfi: strip hashes from static functions

On Thu, Mar 11, 2021 at 6:45 PM Kees Cook <keescook@...omium.org> wrote:
>
> On Thu, Mar 11, 2021 at 04:49:09PM -0800, Sami Tolvanen wrote:
> > With CONFIG_CFI_CLANG and ThinLTO, Clang appends a hash to the names
> > of all static functions not marked __used. This can break userspace
> > tools that don't expect the function name to change, so strip out the
> > hash from the output.
> >
> > Suggested-by: Jack Pham <jackp@...eaurora.org>
> > Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
>
> (Is it possible we could end up with symbol name collisions? ... though
> I guess we would have had collisions before?)

Yes, these are static functions, so name collisions have always been possible.

Sami