linux-hardening - Re: [PATCH v9 01/15] modpost: fix removing numeric suffixes

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Date:   Thu, 23 Dec 2021 17:19:06 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Alexander Lobakin <alexandr.lobakin@...el.com>
Cc:     linux-hardening@...r.kernel.org, x86@...nel.org,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Kristen Carlson Accardi <kristen@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        Ard Biesheuvel <ardb@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Bruce Schlobohm <bruce.schlobohm@...el.com>,
        Jessica Yu <jeyu@...nel.org>,
        kernel test robot <lkp@...el.com>,
        Miroslav Benes <mbenes@...e.cz>,
        Evgenii Shatokhin <eshatokhin@...tuozzo.com>,
        Jonathan Corbet <corbet@....net>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Marios Pomonis <pomonis@...gle.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Nicolas Pitre <nico@...xnic.net>,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-arch@...r.kernel.org, live-patching@...r.kernel.org,
        llvm@...ts.linux.dev, stable@...r.kernel.org
Subject: Re: [PATCH v9 01/15] modpost: fix removing numeric suffixes

On Thu, Dec 23, 2021 at 01:21:55AM +0100, Alexander Lobakin wrote:
> For now, that condition from remove_dot():
> 
> if (m && (s[n + m] == '.' || s[n + m] == 0))
> 
> which was designed to test if it's a dot or a \0 after the suffix
> is never satisfied.
> This is due to that s[n + m] always points to the last digit of a
> numeric suffix, not on the symbol next to it:
> 
> param_set_uint.0, s[n + m] is '0', s[n + m + 1] is '\0'
> 
> So it's off by one and was like that since 2014.

What's the relevance of this? Looking at

  7d02b490e93c ("Kbuild, lto: Drop .number postfixes in modpost")

what you're fixing here is something LTO-related. How do you trigger
this?

For a Cc:stable patch, I'm missing a lot of context.

> `-z uniq-symbol` linker flag which we are planning to use to
				     ^^

Who's "we"?

> simplify livepatching brings numeric suffixes back, fix this.
> Otherwise:
> 
> ERROR: modpost: "param_set_uint.0" [vmlinux] is a static EXPORT_SYMBOL
> 
> Fixes: fcd38ed0ff26 ("scripts: modpost: fix compilation warning")
> Cc: stable@...r.kernel.org # 3.17+
> Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>

...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette