Re: [PATCH v7 2/2] perf inject: Fix itrace branch stack synthesis

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Unconditional dereference of `evsel` in `perf_event__repipe_sample` can cause a SIGSEGV when processing events with unknown IDs.
--

commit f883a5f637221df403997603ff0a3d50c5cf401b
Author: Ian Rogers <irogers@google.com>

perf inject: Fix itrace branch stack synthesis

This commit addresses several issues with synthesizing branch stacks from
AUX data when using "perf inject --itrace=L". It fixes sample types, modifies
event attributes, and addresses multiple parsing, size calculation, and pointer
issues in event repiping paths.

> diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
> index 5f06ee1c14a08..45eb883f86797 100644
> --- a/tools/perf/builtin-inject.c
> +++ b/tools/perf/builtin-inject.c
[ ... ]
> @@ -375,7 +415,67 @@ static int perf_event__repipe_sample(const struct perf_tool *tool,
>  
>  	build_id__mark_dso_hit(tool, event, sample, evsel, machine);
>  
> -	if (inject->itrace_synth_opts.set && sample->aux_sample.size) {
> +	if (inject->itrace_synth_opts.set &&
> +	    (inject->itrace_synth_opts.last_branch ||
> +	     inject->itrace_synth_opts.add_last_branch)) {
> +		union perf_event *event_copy = (void *)inject->event_copy;
> +		struct branch_stack dummy_bs = { .nr = 0, .hw_idx = 0 };
> +		int err;
> +		size_t sz;
> +		u64 orig_type = evsel->core.attr.sample_type;

If machines__deliver_event() encounters a PERF_RECORD_READ event with an
unknown or missing sample ID, evsel may be evaluated to NULL and passed
to this callback. Does this unconditionally dereference evsel, leading to
a crash when analyzing a malformed perf.data file?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260518203805.2955241-1-irogers@google.com?part=2