selftest/bpf: Fix memory leak in kprobe_multi_test

The get_syms() function in kprobe_multi_test.c does not free the string
memory allocated by sscanf correctly. Fix it.

Fixes: 5b6c7e5c ("selftests/bpf: Add attach bench test")
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/bpf/20221011120108.782373-5-xukuohai@huaweicloud.com

tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c

@@ -325,7 +325,7 @@ static bool symbol_equal(const void *key1, const void *key2, void *ctx __maybe_u
 static int get_syms(char ***symsp, size_t *cntp)
 {
 	size_t cap = 0, cnt = 0, i;
-	char *name, **syms = NULL;
+	char *name = NULL, **syms = NULL;
 	struct hashmap *map;
 	char buf[256];
 	FILE *f;
@@ -352,6 +352,8 @@ static int get_syms(char ***symsp, size_t *cntp)
 		/* skip modules */
 		if (strchr(buf, '['))
 			continue;
+
+		free(name);
 		if (sscanf(buf, "%ms$*[^\n]\n", &name) != 1)
 			continue;
 		/*
@@ -369,32 +371,32 @@ static int get_syms(char ***symsp, size_t *cntp)
 		if (!strncmp(name, "__ftrace_invalid_address__",
 			     sizeof("__ftrace_invalid_address__") - 1))
 			continue;
+
 		err = hashmap__add(map, name, NULL);
-		if (err) {
-			free(name);
-			if (err == -EEXIST)
-				continue;
+		if (err == -EEXIST)
+			continue;
+		if (err)
 			goto error;
-		}
+
 		err = libbpf_ensure_mem((void **) &syms, &cap,
 					sizeof(*syms), cnt + 1);
-		if (err) {
-			free(name);
+		if (err)
 			goto error;
-		}
-		syms[cnt] = name;
-		cnt++;
+
+		syms[cnt++] = name;
+		name = NULL;
 	}
 
 	*symsp = syms;
 	*cntp = cnt;
 
 error:
+	free(name);
 	fclose(f);
 	hashmap__free(map);
 	if (err) {
 		for (i = 0; i < cnt; i++)
-			free(syms[cnt]);
+			free(syms[i]);
 		free(syms);
 	}
 	return err;