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

Paul E. McKenney
2023-03-26T04:36:35Z

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
>