linux-hardening - Re: [PATCH 4/4] fortify: Use __builtin_dynamic_object

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <9d80e0a3-3fcc-0676-4529-79743f418557@gotplt.org>
Date:   Wed, 21 Sep 2022 07:43:17 -0400
From:   Siddhesh Poyarekar <siddhesh@...plt.org>
To:     Kees Cook <keescook@...omium.org>, linux-hardening@...r.kernel.org
Cc:     Miguel Ojeda <ojeda@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Tom Rix <trix@...hat.com>, llvm@...ts.linux.dev,
        Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] fortify: Use __builtin_dynamic_object_size() when
 available

On 2022-09-20 15:22, Kees Cook wrote:
> Since the commits starting with c37495d6254c ("slab: add __alloc_size
> attributes for better bounds checking"), the compilers have runtime
> allocation size hints available in some places. This was immediately
> available to CONFIG_UBSAN_BOUNDS, but CONFIG_FORTIFY_SOURCE needed
> updating to explicitly make use the hints via the associated
> __builtin_dynamic_object_size() helper. Detect and use the builtin when
> it is available, increasing the accuracy of the mitigation. When runtime
> sizes are not available, __builtin_dynamic_object_size() falls back to
> __builtin_object_size(), leaving the existing bounds checking unchanged.

I don't know yet what the overhead is for __builtin_dynamic_object_size 
vs __builtin_object_size, were you able to measure it somehow for the 
kernel?  If there's a significant tradeoff, it may make sense to provide 
a user override.

Thanks,
Sid