perf mem: Don't leak mem event names

When preparing the mem events for the argv copies are intentionally
made. These copies are leaked and cause runs of perf using address
sanitizer to fail. Rather than leak the memory allocate a chunk of
memory for the mem event names upfront and build the strings in this -
the storage is sized larger than the previous buffer size. The caller
is then responsible for clearing up this memory. As part of this
change, remove the mem_loads_name and mem_stores_name global buffers
then change the perf_pmu__mem_events_name to write to an out argument
buffer.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Thomas Falcon <thomas.falcon@intel.com>
Reviewed-by: Leo Yan <leo.yan@arm.com>
Link: https://lore.kernel.org/r/20250308012853.1384762-1-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

1 files changed, 40 insertions, 27 deletions

diff --git a/tools/perf/util/mem-events.c b/tools/perf/util/mem-events.c
index 0277d3e1505c..9011784b950d 100644
--- a/tools/perf/util/mem-events.c
+++ b/tools/perf/util/mem-events.c
@@ -31,9 +31,6 @@ struct perf_mem_event perf_mem_events[PERF_MEM_EVENTS__MAX] = {
 
 bool perf_mem_record[PERF_MEM_EVENTS__MAX] = { 0 };
 
-static char mem_loads_name[100];
-static char mem_stores_name[100];
-
 struct perf_mem_event *perf_pmu__mem_events_ptr(struct perf_pmu *pmu, int i)
 {
 	if (i >= PERF_MEM_EVENTS__MAX || !pmu)
@@ -81,7 +78,8 @@ int perf_pmu__mem_events_num_mem_pmus(struct perf_pmu *pmu)
 	return num;
 }
 
-static const char *perf_pmu__mem_events_name(int i, struct perf_pmu *pmu)
+static const char *perf_pmu__mem_events_name(struct perf_pmu *pmu, int i,
+					     char *buf, size_t buf_size)
 {
 	struct perf_mem_event *e;
 
@@ -96,31 +94,31 @@ static const char *perf_pmu__mem_events_name(int i, struct perf_pmu *pmu)
 		if (e->ldlat) {
 			if (!e->aux_event) {
 				/* ARM and Most of Intel */
-				scnprintf(mem_loads_name, sizeof(mem_loads_name),
+				scnprintf(buf, buf_size,
 					  e->name, pmu->name,
 					  perf_mem_events__loads_ldlat);
 			} else {
 				/* Intel with mem-loads-aux event */
-				scnprintf(mem_loads_name, sizeof(mem_loads_name),
+				scnprintf(buf, buf_size,
 					  e->name, pmu->name, pmu->name,
 					  perf_mem_events__loads_ldlat);
 			}
 		} else {
 			if (!e->aux_event) {
 				/* AMD and POWER */
-				scnprintf(mem_loads_name, sizeof(mem_loads_name),
+				scnprintf(buf, buf_size,
 					  e->name, pmu->name);
-			} else
+			} else {
 				return NULL;
+			}
 		}
-
-		return mem_loads_name;
+		return buf;
 	}
 
 	if (i == PERF_MEM_EVENTS__STORE) {
-		scnprintf(mem_stores_name, sizeof(mem_stores_name),
+		scnprintf(buf, buf_size,
 			  e->name, pmu->name);
-		return mem_stores_name;
+		return buf;
 	}
 
 	return NULL;
@@ -238,55 +236,69 @@ void perf_pmu__mem_events_list(struct perf_pmu *pmu)
 	int j;
 
 	for (j = 0; j < PERF_MEM_EVENTS__MAX; j++) {
+		char buf[128];
 		struct perf_mem_event *e = perf_pmu__mem_events_ptr(pmu, j);
 
 		fprintf(stderr, "%-*s%-*s%s",
 			e->tag ? 13 : 0,
 			e->tag ? : "",
 			e->tag && verbose > 0 ? 25 : 0,
-			e->tag && verbose > 0 ? perf_pmu__mem_events_name(j, pmu) : "",
+			e->tag && verbose > 0
+			? perf_pmu__mem_events_name(pmu, j, buf, sizeof(buf))
+			: "",
 			e->supported ? ": available\n" : "");
 	}
 }
 
-int perf_mem_events__record_args(const char **rec_argv, int *argv_nr)
+int perf_mem_events__record_args(const char **rec_argv, int *argv_nr, char **event_name_storage_out)
 {
 	const char *mnt = sysfs__mount();
 	struct perf_pmu *pmu = NULL;
-	struct perf_mem_event *e;
 	int i = *argv_nr;
-	const char *s;
-	char *copy;
 	struct perf_cpu_map *cpu_map = NULL;
-	int ret;
+	size_t event_name_storage_size =
+		perf_pmu__mem_events_num_mem_pmus(NULL) * PERF_MEM_EVENTS__MAX * 128;
+	size_t event_name_storage_remaining = event_name_storage_size;
+	char *event_name_storage = malloc(event_name_storage_size);
+	char *event_name_storage_ptr = event_name_storage;
+
+	if (!event_name_storage)
+		return -ENOMEM;
 
+	*event_name_storage_out = NULL;
 	while ((pmu = perf_pmus__scan_mem(pmu)) != NULL) {
 		for (int j = 0; j < PERF_MEM_EVENTS__MAX; j++) {
-			e = perf_pmu__mem_events_ptr(pmu, j);
+			const char *s;
+			struct perf_mem_event *e = perf_pmu__mem_events_ptr(pmu, j);
+			int ret;
 
 			if (!perf_mem_record[j])
 				continue;
 
 			if (!e->supported) {
+				char buf[128];
+
 				pr_err("failed: event '%s' not supported\n",
-					perf_pmu__mem_events_name(j, pmu));
+					perf_pmu__mem_events_name(pmu, j, buf, sizeof(buf)));
+				free(event_name_storage);
 				return -1;
 			}
 
-			s = perf_pmu__mem_events_name(j, pmu);
+			s = perf_pmu__mem_events_name(pmu, j, event_name_storage_ptr,
+						      event_name_storage_remaining);
 			if (!s || !perf_pmu__mem_events_supported(mnt, pmu, e))
 				continue;
 
-			copy = strdup(s);
-			if (!copy)
-				return -1;
-
 			rec_argv[i++] = "-e";
-			rec_argv[i++] = copy;
+			rec_argv[i++] = event_name_storage_ptr;
+			event_name_storage_remaining -= strlen(event_name_storage_ptr) + 1;
+			event_name_storage_ptr += strlen(event_name_storage_ptr) + 1;
 
 			ret = perf_cpu_map__merge(&cpu_map, pmu->cpus);
-			if (ret < 0)
+			if (ret < 0) {
+				free(event_name_storage);
 				return ret;
+			}
 		}
 	}
 
@@ -301,6 +313,7 @@ int perf_mem_events__record_args(const char **rec_argv, int *argv_nr)
 	}
 
 	*argv_nr = i;
+	*event_name_storage_out = event_name_storage;
 	return 0;
 }