linux-hardening - Re: [PATCH] arm64: Support Clang UBSAN trap codes for better reporting

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Date:   Fri, 3 Feb 2023 16:36:04 +0000
From:   Kees Cook <keescook@...omium.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        John Stultz <jstultz@...gle.com>,
        Yongqin Liu <yongqin.liu@...aro.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Yury Norov <yury.norov@...il.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Marco Elver <elver@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, llvm@...ts.linux.dev,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] arm64: Support Clang UBSAN trap codes for better
 reporting

On Fri, Feb 03, 2023 at 12:34:38PM +0100, Ard Biesheuvel wrote:
> [...]
> > +       switch (check_type) {
> > +       case ubsan_add_overflow:
> > +               return "UBSAN: addition overflow";
> 
> It would be nice if we could avoid duplicating this UBSAN: prefix 21x times.

Yeah, agreed. I didn't see a way around it without weirdness or loss of
details. die() takes a string not a format string, so without really
odd shenanigans (re-write a single string in memory?) this is the most
straight forward. One idea, though, is to drop all the strings that'll
never happen -- i.e. wrap individual case statements in the associated
CONFIG_UBSAN_foo. I already dropped several strings that were never
implemented in the kernel's UBSAN. I could be even more picky. I'll try
this in v2...

-- 
Kees Cook