Re: [PATCH v2 0/2] Rust KCFI support

[Gatlin Newhouse]

On Thu, Aug 01, 2024 at 01:35:16PM UTC, Alice Ryhl wrote:
> The control flow integrity (kCFI) sanitizer is an important sanitizer
> that is often used in production. This patch series makes it possible to
> use kCFI and Rust together.
> 
> The second patch in this series depends on the next version of [1],
> which Miguel will send soon. It also depends on [2].
> 
> Link: https://lore.kernel.org/r/20240709160615.998336-12-ojeda@xxxxxxxxxx [1]
> Link: https://lore.kernel.org/r/20240730-target-json-arrays-v1-1-2b376fd0ecf4@xxxxxxxxxx [2]
> Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> ---
> Changes in v2:
> - Fix for FineIBT.
> - Add more info to commit messages and config descrptions.
> - Link to v1: https://lore.kernel.org/r/20240730-kcfi-v1-0-bbb948752a30@xxxxxxxxxx
> 
> ---
> Alice Ryhl (1):
>       cfi: add CONFIG_CFI_ICALL_NORMALIZE_INTEGERS
> 
> Matthew Maurer (1):
>       rust: cfi: add support for CFI_CLANG with Rust
> 
>  Makefile                        | 10 ++++++++++
>  arch/Kconfig                    | 16 ++++++++++++++++
>  arch/x86/Makefile               |  4 ++++
>  init/Kconfig                    |  4 +++-
>  rust/Makefile                   |  2 +-
>  scripts/generate_rust_target.rs |  1 +
>  6 files changed, 35 insertions(+), 2 deletions(-)

To test this patch: I started from v6.11-rc3 tag and applied the new version of
Miguel's RUSTC_VERSION_TEXT patch [1] and the Support Arrays in Target JSON
patch [2], before applying this patch. I am on Rust's beta channel and
Clang/LLVM 19.

I also built a v6.11-rc3 kernel without these patches to establish a baseline
for LKDTM output in dmesg when testing CFI [3]. I built the v6.11-rc3 kernel by
starting with an x86_64_defconfig, then enabling CFI_CLANG, CFI_PERMISSIVE, and
LKDTM.

When applying [1], there was an patch does not apply error. I had to manually
change the init/Kconfig RUSTC_VERSION_TEXT to Miguel's change in [1]. No issues
encountered applying [2] afterwards. Similarly, was able to automerge this
patch without any issues.

Then I built the kernel starting with x86_64_defconfig and enabling: RUST,
CFI_CLANG, CFI_ICALL_NORMALIZE_INTEGERS, CFI_PERMISSIVE and LKDTM. Compiled the
kernel, load into qemu with Busybox rootfs, test CFI within LKDTM per Kees's
blog [3]. I saw the same expected behavior from LKDTM after applying these
patches when compared with the behavior from LKDTM on a v6.11-rc3 build without
these patches.

Link: https://lore.kernel.org/lkml/20240808221138.873750-1-ojeda@xxxxxxxxxx/ [1]
Link: https://lore.kernel.org/all/20240730-target-json-arrays-v1-1-2b376fd0ecf4@xxxxxxxxxx/ [2]
Link: https://outflux.net/blog/archives/2019/11/20/experimenting-with-clang-cfi-on-upstream-linux/ [3]

Tested-by: Gatlin Newhouse <gatlin.newhouse@xxxxxxxxx>

--
Gatlin Newhouse