[SRU][N][PATCH v3 2/2] libperf cpumap: Ensure empty cpumap is NULL from alloc

[Mehmet Basaran]

From: Ian Rogers <irogers at google.com>

BugLink: https://bugs.launchpad.net/bugs/2107336

commit dcd45b376d0ab07b987fa968a01e7a5b0c4bf837 upstream.

Potential corner cases could cause a cpumap to be allocated with size
0, but an empty cpumap should be represented as NULL. Add a path in
perf_cpu_map__alloc() to ensure this.

Suggested-by: James Clark <james.clark at arm.com>
Signed-off-by: Ian Rogers <irogers at google.com>
Acked-by: Namhyung Kim <namhyung at kernel.org>
Cc: Adrian Hunter <adrian.hunter at intel.com>
Cc: Alexander Shishkin <alexander.shishkin at linux.intel.com>
Cc: Alexandre Ghiti <alexghiti at rivosinc.com>
Cc: Andrew Jones <ajones at ventanamicro.com>
Cc: André Almeida <andrealmeid at igalia.com>
Cc: Athira Rajeev <atrajeev at linux.vnet.ibm.com>
Cc: Atish Patra <atishp at rivosinc.com>
Cc: Changbin Du <changbin.du at huawei.com>
Cc: Darren Hart <dvhart at infradead.org>
Cc: Davidlohr Bueso <dave at stgolabs.net>
Cc: Huacai Chen <chenhuacai at kernel.org>
Cc: Ingo Molnar <mingo at redhat.com>
Cc: Jiri Olsa <jolsa at kernel.org>
Cc: John Garry <john.g.garry at oracle.com>
Cc: K Prateek Nayak <kprateek.nayak at amd.com>
Cc: Kajol Jain <kjain at linux.ibm.com>
Cc: Kan Liang <kan.liang at linux.intel.com>
Cc: Leo Yan <leo.yan at linaro.org>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Mike Leach <mike.leach at linaro.org>
Cc: Nick Desaulniers <ndesaulniers at google.com>
Cc: Paolo Bonzini <pbonzini at redhat.com>
Cc: Paran Lee <p4ranlee at gmail.com>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Ravi Bangoria <ravi.bangoria at amd.com>
Cc: Sandipan Das <sandipan.das at amd.com>
Cc: Sean Christopherson <seanjc at google.com>
Cc: Steinar H. Gunderson <sesse at google.com>
Cc: Suzuki Poulouse <suzuki.poulose at arm.com>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Will Deacon <will at kernel.org>
Cc: Yang Jihong <yangjihong1 at huawei.com>
Cc: Yang Li <yang.lee at linux.alibaba.com>
Cc: Yanteng Si <siyanteng at loongson.cn>
Closes: https://lore.kernel.org/lkml/2cd09e7c-eb88-6726-6169-647dcd0a8101@arm.com/
Link: https://lore.kernel.org/r/20240202234057.2085863-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme at redhat.com>
(cherry picked from commit dcd45b376d0ab07b987fa968a01e7a5b0c4bf837)
Signed-off-by: Mehmet Basaran <mehmet.basaran at canonical.com>
---
 tools/lib/perf/cpumap.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
index ba49552952c5..cae799ad44e1 100644
--- a/tools/lib/perf/cpumap.c
+++ b/tools/lib/perf/cpumap.c
@@ -18,9 +18,13 @@ void perf_cpu_map__set_nr(struct perf_cpu_map *map, int nr_cpus)
 
 struct perf_cpu_map *perf_cpu_map__alloc(int nr_cpus)
 {
-	RC_STRUCT(perf_cpu_map) *cpus = malloc(sizeof(*cpus) + sizeof(struct perf_cpu) * nr_cpus);
+	RC_STRUCT(perf_cpu_map) *cpus;
 	struct perf_cpu_map *result;
 
+	if (nr_cpus == 0)
+		return NULL;
+
+	cpus = malloc(sizeof(*cpus) + sizeof(struct perf_cpu) * nr_cpus);
 	if (ADD_RC_CHK(result, cpus)) {
 		cpus->nr = nr_cpus;
 		refcount_set(&cpus->refcnt, 1);
-- 
2.43.0