linux-kernel - Re: [PATCH 0/8] tools/nolibc: add support for stack protector

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Date:   Sat, 25 Mar 2023 21:36:28 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Willy Tarreau <w@....eu>
Cc:     linux@...ssschuh.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/8] tools/nolibc: add support for stack protector

On Sat, Mar 25, 2023 at 04:45:08PM +0100, Willy Tarreau wrote:
> Hello Paul,
> 
> This is essentially Thomas' work so instead of paraphrasing his work,
> I'm pasting his description below. I've tested his changes on all
> supported archs, applied a tiny modification with his permission
> to continue to support passing CFLAGS, and for me this is all fine.
> In a short summary this adds support for stack protector to i386 and
> x86_64 in nolibc, and the accompanying test to the selftest program.
> 
> A new test category was added, "protection", which currently has a
> single test. Archs that support it will report "OK" there and those
> that do not will report "SKIPPED", as is already the case for tests
> that cannot be run.
> 
> This was applied on top of your dev.2023.03.20a branch. I'm reasonably
> confident with the nature of the changes, so if your queue for 6.4 is
> not closed yet, it can be a good target, otherwise 6.5 will be fine as
> well.

I have applied and pushed it out, thank you both!

We are a little late in the process, but if testing goes well, I can't
see why this cannot make the v6.4 merge window.

							Thanx, Paul

> Thanks in advance!
> Willy
> 
> Thomas' description below:
> 
> This is useful when using nolibc for security-critical tools.
> Using nolibc has the advantage that the code is easily auditable and
> sandboxable with seccomp as no unexpected syscalls are used.
> Using compiler-assistent stack protection provides another security
> mechanism.
> 
> For this to work the compiler and libc have to collaborate.
> 
> This patch adds the following parts to nolibc that are required by the
> compiler:
> 
> * __stack_chk_guard: random sentinel value
> * __stack_chk_fail: handler for detected stack smashes
> 
> In addition an initialization function is added that randomizes the
> sentinel value.
> 
> Only support for global guards is implemented.
> Register guards are useful in multi-threaded context which nolibc does
> not provide support for.
> 
> Link: https://lwn.net/Articles/584225/
> 
> 
> Thomas Weißschuh (8):
>   tools/nolibc: add definitions for standard fds
>   tools/nolibc: add helpers for wait() signal exits
>   tools/nolibc: tests: constify test_names
>   tools/nolibc: add support for stack protector
>   tools/nolibc: tests: fold in no-stack-protector cflags
>   tools/nolibc: tests: add test for -fstack-protector
>   tools/nolibc: i386: add stackprotector support
>   tools/nolibc: x86_64: add stackprotector support
> 
>  tools/include/nolibc/Makefile                |  4 +-
>  tools/include/nolibc/arch-i386.h             |  7 ++-
>  tools/include/nolibc/arch-x86_64.h           |  5 ++
>  tools/include/nolibc/nolibc.h                |  1 +
>  tools/include/nolibc/stackprotector.h        | 53 ++++++++++++++++
>  tools/include/nolibc/types.h                 |  2 +
>  tools/include/nolibc/unistd.h                |  5 ++
>  tools/testing/selftests/nolibc/Makefile      | 11 +++-
>  tools/testing/selftests/nolibc/nolibc-test.c | 64 +++++++++++++++++++-
>  9 files changed, 144 insertions(+), 8 deletions(-)
>  create mode 100644 tools/include/nolibc/stackprotector.h
> 
> -- 
> 2.17.5
>