linux-kernel - Re: [PATCH v3 0/7] x86/cfi,bpf: Fix CFI vs eBPF

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Date: Fri, 15 Dec 2023 16:53:48 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Peter Zijlstra <peterz@...radead.org>, Ilya Leoshkevich <iii@...ux.ibm.com>, 
	Martin KaFai Lau <martin.lau@...nel.org>
Cc: Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, X86 ML <x86@...nel.org>, 
	"H. Peter Anvin" <hpa@...or.com>, "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, Arnd Bergmann <arnd@...db.de>, 
	Sami Tolvanen <samitolvanen@...gle.com>, Kees Cook <keescook@...omium.org>, 
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, 
	linux-riscv <linux-riscv@...ts.infradead.org>, LKML <linux-kernel@...r.kernel.org>, 
	Network Development <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>, 
	linux-arch <linux-arch@...r.kernel.org>, clang-built-linux <llvm@...ts.linux.dev>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, Joao Moreira <joao@...rdrivepizza.com>, 
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v3 0/7] x86/cfi,bpf: Fix CFI vs eBPF

On Fri, Dec 15, 2023 at 1:33 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> Hi!
>
> What started with the simple observation that bpf_dispatcher_*_func() was
> broken for calling CFI functions with a __nocfi calling context for FineIBT
> ended up with a complete BPF wide CFI fixup.
>
> With these changes on the BPF selftest suite passes without crashing -- there's
> still a few failures, but Alexei has graciously offered to look into those.
>
> (Alexei, I have presumed your SoB on the very last patch, please update
> as you see fit)
>
> Changes since v2 are numerous but include:
>  - cfi_get_offset() -- as a means to communicate the offset (ast)
>  - 5 new patches fixing various BPF internals to be CFI clean

Looks great to me. Pushed to bpf-next.

There is a failure on s390 that I temporarily denylisted
with an extra patch.
And sent a proposed fix:
https://lore.kernel.org/bpf/20231216004549.78355-1-alexei.starovoitov@gmail.com/

Ilya,
please take a look.

> Note: it *might* be possible to merge the
> bpf_bpf_tcp_ca.c:unsupported_ops[] thing into the CFI stubs, as is
> get_info will have a NULL stub, unlike the others.

That's a good idea. Will clean up unsupported_ops.
Either myself or Martin will follow up.