Commit a0a41736 authored Dec 03, 2025 by Ian Rogers Committed by Namhyung Kim Dec 04, 2025

libperf cpumap: Fix perf_cpu_map__max for an empty/NULL map



Passing an empty map to perf_cpu_map__max triggered a SEGV. Explicitly
test for the empty map.

Reported-by: Ingo Molnar <mingo@kernel.org>
Closes: https://lore.kernel.org/linux-perf-users/aSwt7yzFjVJCEmVp@gmail.com/


Tested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

parent 6744c0b1

tools/lib/perf/cpumap.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -368,10 +368,12 @@ struct perf_cpu perf_cpu_map__max(const struct perf_cpu_map *map)
		.cpu = -1
		};

		// cpu_map__trim_new() qsort()s it, cpu_map__default_new() sorts it as well.
		return __perf_cpu_map__nr(map) > 0
		? __perf_cpu_map__cpu(map, __perf_cpu_map__nr(map) - 1)
		: result;
		if (!map)
		return result;

		// The CPUs are always sorted and nr is always > 0 as 0 length map is
		// encoded as NULL.
		return __perf_cpu_map__cpu(map, __perf_cpu_map__nr(map) - 1);
		}

		/** Is 'b' a subset of 'a'. */