linux-kernel - Re: [PATCH v1 0/3] Fix use-after-free race in bpf_prog

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Message-ID: <CAP-5=fVwFw0ZjCcvakmk_Ay+v8U_W_HKc+irqw-jR2hMTxqWZA@mail.gmail.com>
Date: Tue, 2 Sep 2025 15:33:53 -0700
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	Blake Jones <blakejones@...gle.com>, Zhongqiu Han <quic_zhonhan@...cinc.com>, 
	Andrii Nakryiko <andrii@...nel.org>, Song Liu <songliubraving@...com>, 
	Dave Marchevsky <davemarchevsky@...com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org, 
	Howard Chu <howardchu95@...il.com>, song@...nel.org, 
	Yonghong Song <yonghong.song@...ux.dev>
Subject: Re: [PATCH v1 0/3] Fix use-after-free race in bpf_prog_info synthesis

On Tue, Sep 2, 2025 at 2:54 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> Hi Ian,
>
> On Tue, Sep 02, 2025 at 11:17:10AM -0700, Ian Rogers wrote:
> > The addition of more use of bpf_prog_info for gather BPF metadata in:
> > https://lore.kernel.org/all/20250612194939.162730-1-blakejones@google.com/
> > and the ever richer perf trace testing, such as:
> > https://lore.kernel.org/all/20250528191148.89118-1-howardchu95@gmail.com/
> > frequently triggered a latent perf bug in v6.17 when the perf and
> > libbpf updates came together. The bug would cause segvs and was reported here:
> > https://lore.kernel.org/lkml/CAP-5=fWJQcmUOP7MuCA2ihKnDAHUCOBLkQFEkQES-1ZZTrgf8Q@mail.gmail.com/
> >
> > To fix the issue the 1st and 3rd patch are necessary. Both patches
> > address a race of either the sideband thread updating perf's state or
> > the kernel state changing over two system calls.
>
> Thanks a lot for the fix!

Thanks, your reproduction was a great help.

> >
> > The use-after-free was introduced by:
> > https://lore.kernel.org/r/20241205084500.823660-4-quic_zhonhan@quicinc.com
> > The lack of failing getting the bpf_prog_info for changes in the
> > kernel was introduced in:
> > https://lore.kernel.org/r/20211011082031.4148337-4-davemarchevsky@fb.com
> >
> > As v6.17 is currently actively segv-ing in perf test I'd recommend
> > these patches go into v6.17 asap.
>
> Sure, I'll add them to perf-tools tree.
>
> >
> > When running the perf tests on v6.17 I frequently see less critical
> > test failures addressed in:
> > https://lore.kernel.org/all/20250821221834.1312002-1-irogers@google.com/
>
> Are they all from v6.17?

We could wait for the backports to v6.17.1, they all have fixes tags.
They are more cosmetic things than this set of fixes.

Thanks,
Ian

>
> >
> > Ian Rogers (3):
> >   perf bpf-event: Fix use-after-free in synthesis
> >   perf bpf-utils: Constify bpil_array_desc
> >   perf bpf-utils: Harden get_bpf_prog_info_linear
>
> Reviewed-by: Namhyung Kim <namhyung@...nel.org>
>
> Thanks,
> Namhyung
>
> >
> >  tools/perf/util/bpf-event.c | 39 ++++++++++++++++--------
> >  tools/perf/util/bpf-utils.c | 61 ++++++++++++++++++++++++-------------
> >  2 files changed, 66 insertions(+), 34 deletions(-)
> >
> > --
> > 2.51.0.355.g5224444f11-goog
> >