From 6b4f044d9cd8a61cfd6ec1e9774ac48b29fcc646 Mon Sep 17 00:00:00 2001 From: Ian Rogers Date: Wed, 3 Dec 2025 13:47:01 -0800 Subject: [PATCH] libperf cpumap: Fix perf_cpu_map__max for an empty/NULL map [ Upstream commit a0a4173631bfcfd3520192c0a61cf911d6a52c3a ] Passing an empty map to perf_cpu_map__max triggered a SEGV. Explicitly test for the empty map. Reported-by: Ingo Molnar Closes: https://lore.kernel.org/linux-perf-users/aSwt7yzFjVJCEmVp@gmail.com/ Tested-by: Ingo Molnar Signed-off-by: Ian Rogers Tested-by: Thomas Richter Signed-off-by: Namhyung Kim Signed-off-by: Sasha Levin --- tools/lib/perf/cpumap.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c index cae799ad44e13..e5938b91199f3 100644 --- a/tools/lib/perf/cpumap.c +++ b/tools/lib/perf/cpumap.c @@ -409,10 +409,12 @@ 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'. */ -- 2.47.3