linux-kernel - 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...