Re: [PATCH v3 1/3] perf evsel: don't set PERF_SAMPLE_IP for unprivileged tracepoints

sashiko-bot
2026-04-23T22:14:48Z

Sashiko AI review found 1 potential issue(s):
- [High] Unconditionally dropping PERF_SAMPLE_IP for unprivileged tracepoints breaks user-space dynamic tracing (uprobes and USDTs).
--

commit 06030eb0792514412c01e8660eaafa6292e09335
Author: Anubhav Shelat <ashelat@redhat.com>

perf evsel: don't set PERF_SAMPLE_IP for unprivileged tracepoints

This commit conditionally drops the PERF_SAMPLE_IP bit for tracepoint events
configured by unprivileged users. It aims to prevent exposing kernel addresses
that might reveal the KASLR base offset.

> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index f59228c1a39eb..a1091d937ff92 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
[ ... ]
> @@ -1503,7 +1503,9 @@ void evsel__config(struct evsel *evsel, struct record_opts *opts,
> attr->write_backward = opts->overwrite ? 1 : 0;
> attr->read_format = PERF_FORMAT_LOST;
>
> - evsel__set_sample_bit(evsel, IP);
> + if (attr->type != PERF_TYPE_TRACEPOINT || perf_event_paranoid_check(1))
> + evsel__set_sample_bit(evsel, IP);
> +

Uprobes and USDTs are also registered as PERF_TYPE_TRACEPOINT events, but their
instruction pointer is a safe user-space address indicating where the breakpoint
fired, rather than a kernel address that could leak KASLR.

By unconditionally skipping the IP bit for all tracepoints when executed by
an unprivileged user, downstream tools might fail to resolve symbols
or attribute hits to specific instructions for user-space events.

Does this inadvertently break user-space dynamic tracing?

> evsel__set_sample_bit(evsel, TID);
>
> if (evsel->sample_read) {

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Sashiko AI review · https://sashiko.dev/#/patchset/20260423151746.16258-1-ashelat@redhat.com?part=1