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libperf cpumap: Fix perf_cpu_map__max for an empty/NULL map

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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>
This commit is contained in:
Ian Rogers 2025-12-03 13:47:01 -08:00 committed by Namhyung Kim
parent 6744c0b182
commit a0a4173631
1 changed files with 6 additions and 4 deletions
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10
tools/lib/perf/cpumap.c
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@ -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'. */