From: Ian Rogers <irogers@google.com>
Date: Sun, 14 Sep 2025 18:33:53 +0000 (-0700)
Subject: perf sched: Avoid union type punning undefined behavior
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=58a606149c60d5da554302a7a08234cf3ca259f4;p=users%2Fhch%2Fmisc.git

perf sched: Avoid union type punning undefined behavior

A union is used to set the priv value in thread (a void*) to a boolean
value through type punning. Undefined behavior sanitizer fails on this.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index f166d6cbc083..eca3b1c58c4b 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -1532,35 +1532,24 @@ static int process_sched_wakeup_ignore(const struct perf_tool *tool __maybe_unus
 	return 0;
 }
 
-union map_priv {
-	void	*ptr;
-	bool	 color;
-};
-
 static bool thread__has_color(struct thread *thread)
 {
-	union map_priv priv = {
-		.ptr = thread__priv(thread),
-	};
-
-	return priv.color;
+	return thread__priv(thread) != NULL;
 }
 
 static struct thread*
 map__findnew_thread(struct perf_sched *sched, struct machine *machine, pid_t pid, pid_t tid)
 {
 	struct thread *thread = machine__findnew_thread(machine, pid, tid);
-	union map_priv priv = {
-		.color = false,
-	};
+	bool color = false;
 
 	if (!sched->map.color_pids || !thread || thread__priv(thread))
 		return thread;
 
 	if (thread_map__has(sched->map.color_pids, tid))
-		priv.color = true;
+		color = true;
 
-	thread__set_priv(thread, priv.ptr);
+	thread__set_priv(thread, color ? ((void*)1) : NULL);
 	return thread;
 }