isisd: fix memory leak for MT settings static buffers

The multi-topology code in isis_mt.c uses three static buffers to avoid
repeated memory allocations during MT settings lookups. These buffers
are allocated using XREALLOC in area_mt_settings(), circuit_mt_settings(),
and circuit_bcast_mt_set(), growing as needed but never freed during
daemon shutdown.

This causes the memory leak checker to report three "ISIS MT Area Setting"
allocations per router at exit time, as the static buffers persist until
process termination without being properly released.

The fix moves these function-local static variables to file scope and
adds a new mt_fini() cleanup function that frees all three buffers during
daemon termination. This function is called from terminate() in isis_main.c
alongside the other cleanup functions, ensuring proper memory release
when isisd exits.

Signed-off-by: Vincent Jardin <vjardin@free.fr>

Author: vjardin

isisd/isis_main.c

@@ -105,6 +105,7 @@ static FRR_NORETURN void terminate(int i)
 	isis_terminate();
 	isis_sr_term();
 	isis_srv6_term();
+	mt_fini();
 	isis_zebra_stop();
 
 	isis_master_terminate();

isisd/isis_mt.c

@@ -19,6 +19,14 @@ DEFINE_MTYPE_STATIC(ISISD, MT_AREA_SETTING, "ISIS MT Area Setting");
 DEFINE_MTYPE_STATIC(ISISD, MT_CIRCUIT_SETTING, "ISIS MT Circuit Setting");
 DEFINE_MTYPE_STATIC(ISISD, MT_ADJ_INFO, "ISIS MT Adjacency Info");
 
+/* Static buffers for MT settings - freed by mt_fini() */
+static struct isis_area_mt_setting **area_mt_setting_buf;
+static unsigned int area_mt_setting_buf_size;
+static struct isis_circuit_mt_setting **circuit_mt_setting_buf;
+static unsigned int circuit_mt_setting_buf_size;
+static uint16_t *circuit_bcast_mt_set_buf;
+static unsigned int circuit_bcast_mt_set_buf_size;
+
 bool isis_area_ipv6_dstsrc_enabled(struct isis_area *area)
 {
 	struct isis_area_mt_setting *area_mt_setting;
@@ -213,9 +221,6 @@ bool area_is_mt(struct isis_area *area)
 struct isis_area_mt_setting **area_mt_settings(struct isis_area *area,
 					       unsigned int *mt_count)
 {
-	static unsigned int size = 0;
-	static struct isis_area_mt_setting **rv = NULL;
-
 	unsigned int count = 0;
 	struct listnode *node;
 	struct isis_area_mt_setting *setting;
@@ -225,16 +230,17 @@ struct isis_area_mt_setting **area_mt_settings(struct isis_area *area,
 			continue;
 
 		count++;
-		if (count > size) {
-			rv = XREALLOC(MTYPE_MT_AREA_SETTING, rv,
-				      count * sizeof(*rv));
-			size = count;
+		if (count > area_mt_setting_buf_size) {
+			area_mt_setting_buf = XREALLOC(
+				MTYPE_MT_AREA_SETTING, area_mt_setting_buf,
+				count * sizeof(*area_mt_setting_buf));
+			area_mt_setting_buf_size = count;
 		}
-		rv[count - 1] = setting;
+		area_mt_setting_buf[count - 1] = setting;
 	}
 
 	*mt_count = count;
-	return rv;
+	return area_mt_setting_buf;
 }
 
 /* Circuit specific MT settings api */
@@ -313,9 +319,6 @@ static int circuit_write_mt_settings(struct isis_circuit *circuit,
 struct isis_circuit_mt_setting **
 circuit_mt_settings(struct isis_circuit *circuit, unsigned int *mt_count)
 {
-	static unsigned int size = 0;
-	static struct isis_circuit_mt_setting **rv = NULL;
-
 	struct isis_area_mt_setting **area_settings;
 	unsigned int area_count;
 
@@ -341,16 +344,17 @@ circuit_mt_settings(struct isis_circuit *circuit, unsigned int *mt_count)
 			continue;
 
 		count++;
-		if (count > size) {
-			rv = XREALLOC(MTYPE_MT_AREA_SETTING, rv,
-				      count * sizeof(*rv));
-			size = count;
+		if (count > circuit_mt_setting_buf_size) {
+			circuit_mt_setting_buf = XREALLOC(
+				MTYPE_MT_AREA_SETTING, circuit_mt_setting_buf,
+				count * sizeof(*circuit_mt_setting_buf));
+			circuit_mt_setting_buf_size = count;
 		}
-		rv[count - 1] = setting;
+		circuit_mt_setting_buf[count - 1] = setting;
 	}
 
 	*mt_count = count;
-	return rv;
+	return circuit_mt_setting_buf;
 }
 
 /* ADJ specific MT API */
@@ -478,8 +482,6 @@ static void mt_set_add(uint16_t **mt_set, unsigned int *size,
 static uint16_t *circuit_bcast_mt_set(struct isis_circuit *circuit, int level,
 				      unsigned int *mt_count)
 {
-	static uint16_t *rv;
-	static unsigned int size;
 	struct listnode *node;
 	struct isis_adjacency *adj;
 
@@ -494,11 +496,13 @@ static uint16_t *circuit_bcast_mt_set(struct isis_circuit *circuit, int level,
 		if (adj->adj_state != ISIS_ADJ_UP)
 			continue;
 		for (unsigned int i = 0; i < adj->mt_count; i++)
-			mt_set_add(&rv, &size, &count, adj->mt_set[i]);
+			mt_set_add(&circuit_bcast_mt_set_buf,
+				   &circuit_bcast_mt_set_buf_size, &count,
+				   adj->mt_set[i]);
 	}
 
 	*mt_count = count;
-	return rv;
+	return circuit_bcast_mt_set_buf;
 }
 
 static void tlvs_add_mt_set(struct isis_area *area, struct isis_tlvs *tlvs,
@@ -557,3 +561,13 @@ void mt_init(void)
 		      circuit_write_mt_settings);
 #endif
 }
+
+void mt_fini(void)
+{
+	XFREE(MTYPE_MT_AREA_SETTING, area_mt_setting_buf);
+	area_mt_setting_buf_size = 0;
+	XFREE(MTYPE_MT_AREA_SETTING, circuit_mt_setting_buf);
+	circuit_mt_setting_buf_size = 0;
+	XFREE(MTYPE_MT_AREA_SETTING, circuit_bcast_mt_set_buf);
+	circuit_bcast_mt_set_buf_size = 0;
+}

isisd/isis_mt.h

@@ -110,4 +110,5 @@ void tlvs_add_mt_bcast(struct isis_tlvs *tlvs, struct isis_circuit *circuit,
 void tlvs_add_mt_p2p(struct isis_tlvs *tlvs, struct isis_circuit *circuit,
 		     uint8_t *id, uint32_t metric);
 void mt_init(void);
+void mt_fini(void);
 #endif