linux-hardening - Re: Progress on Bounds Checking in C and the Linux Kernel

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Date:   Thu, 25 May 2023 12:40:48 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-hardening@...r.kernel.org
Subject: Re: Progress on Bounds Checking in C and the Linux Kernel

On Tue, May 16, 2023 at 01:29:28PM -0700, Kees Cook wrote:
> Hi!
> 
> I just wanted to share links to the presentation Gustavo and I gave at
> last week's Linux Security Summit. Repeating the abstract here, just so
> you don't have to click through if you don't want to:
> 
> 
> Linux, like all C code, regularly suffers from heap buffer overflow
> flaws. Especially frustrating is that the compiler usually has enough
> context to have been able to stop the overflow but has been hampered by
> needing to support legacy coding styles, ambiguous language definitions,
> and fragile APIs. This has forced the compiler to frequently ignore the
> intent of programmers in an effort to support sloppy code patterns that
> may not exist in a project at all.
> 
> The history of the C language specification's "flex array member" (FAM)
> is long and twisty, and technical debt exists due to ambiguous
> implementations. With the introduction of -fstrict-flex-arrays, C can
> now unambiguously declare array sizes. In the kernel we can build on
> this, by transforming trailing zero-length and one-element arrays into
> modern C99 FAMs, adding the use of __builtin_dynamic_object_size(),
> applying it to defenses like FORTIFY_SOURCE, and expanding where the
> compiler can use this knowledge internally for improving existing
> sanitizers. Finally, adding a new struct member attribute, we can expand
> object size tracking to cover all array types, freeing Linux from this
> persistent class of buffer overflows flaws.
> 
> 
> Summary: https://lssna2023.sched.com/event/34dfdb61ccf86035c031b5bf2173765a
> Slides:  https://outflux.net/slides/2023/lss-na/bounds-checking.pdf
> 
> I haven't seen any video published yet, but if that shows up soon, I'll
> reply to this thread with a link.

The video is finally out: https://www.youtube.com/watch?v=V2kzptQG5_A

Thanks
--
Gustavo