netdev - Re: [PATCH v2 2/2] x86/cfi,bpf: Fix BPF JIT call

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Date: Mon, 4 Dec 2023 12:11:28 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Song Liu <song@...nel.org>, Song Liu <songliubraving@...a.com>,
	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>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	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 v2 2/2] x86/cfi,bpf: Fix BPF JIT call

On Mon, Dec 04, 2023 at 10:13:34AM +0100, Peter Zijlstra wrote:

> > Just running test_progs it splats right away:
> > 
> > [   74.047757] kmemleak: Found object by alias at 0xffffffffa0001d80
> > [   74.048272] CPU: 14 PID: 104 Comm: kworker/14:0 Tainted: G        W
> >  O       6.7.0-rc3-00702-g41c30fec304d-dirty #5241
> > [   74.049118] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> > BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
> > [   74.050042] Workqueue: events bpf_prog_free_deferred
> > [   74.050448] Call Trace:
> > [   74.050663]  <TASK>
> > [   74.050841]  dump_stack_lvl+0x55/0x80
> > [   74.051141]  __find_and_remove_object+0xdb/0x110
> > [   74.051521]  kmemleak_free+0x41/0x70
> > [   74.051828]  vfree+0x36/0x130
> 
> Durr, I'll see if I can get that stuff running locally, and otherwise
> play with the robot as you suggested. Thanks!

I think it is bpf_jit_binary_pack_hdr(), which is using prog->bpf_func
as a start address for the image, instead of jit_data->image.

This used to be true, but now it's offset.

Let me see what to do about that...