bugfix: mdns_service_txt_set() wasn't allocating memory for TXT records

Allocation was happening later, causing possible use of stack variables
of caller function, which could be invalid.

Signed-off-by: Piyush Shah <piyush@espressif.com>

components/mdns/mdns.c

@@ -1756,6 +1756,17 @@ static mdns_txt_linked_item_t * _mdns_allocate_txt(size_t num_items, mdns_txt_it
     }
     return new_txt;
 }
+static void _mdns_free_linked_txt(mdns_txt_linked_item_t *txt)
+{
+    mdns_txt_linked_item_t *t;
+    while (txt) {
+        t = txt;
+        txt = txt->next;
+        free((char *)t->value);
+        free((char *)t->key);
+        free(t);
+    }
+}
 
 /**
  * @brief  creates/allocates new service
@@ -3636,14 +3647,8 @@ static void _mdns_execute_action(mdns_action_t * action)
         service = action->data.srv_txt_replace.service->service;
         txt = service->txt;
         service->txt = NULL;
-        while (txt) {
-            t = txt;
-            txt = txt->next;
-            free((char *)t->value);
-            free((char *)t->key);
-            free(t);
-        }
-        service->txt = _mdns_allocate_txt(action->data.srv_txt_replace.num_items, action->data.srv_txt_replace.txt);
+        _mdns_free_linked_txt(txt);
+        service->txt = action->data.srv_txt_replace.txt;
         _mdns_announce_all_pcbs(&action->data.srv_txt_replace.service, 1, false);
 
         break;
@@ -4224,27 +4229,25 @@ esp_err_t mdns_service_txt_set(const char * service, const char * proto, mdns_tx
         return ESP_ERR_NOT_FOUND;
     }
 
-    mdns_txt_item_t * txt_copy = NULL;
+    mdns_txt_linked_item_t * new_txt = NULL;
     if (num_items){
-        txt_copy = (mdns_txt_item_t *)malloc(num_items * sizeof(mdns_txt_item_t));
-        if (!txt_copy) {
+        new_txt = _mdns_allocate_txt(num_items, txt);
+        if (!new_txt) {
             return ESP_ERR_NO_MEM;
         }
-        memcpy(txt_copy, txt, num_items * sizeof(mdns_txt_item_t));
     }
 
     mdns_action_t * action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
     if (!action) {
-        free(txt_copy);
+        _mdns_free_linked_txt(new_txt);
         return ESP_ERR_NO_MEM;
     }
     action->type = ACTION_SERVICE_TXT_REPLACE;
     action->data.srv_txt_replace.service = s;
-    action->data.srv_txt_replace.num_items = num_items;
-    action->data.srv_txt_replace.txt = txt_copy;
+    action->data.srv_txt_replace.txt = new_txt;
 
     if (xQueueSend(_mdns_server->action_queue, &action, (portTickType)0) != pdPASS) {
-        free(txt_copy);
+        _mdns_free_linked_txt(new_txt);
         free(action);
         return ESP_ERR_NO_MEM;
     }

components/mdns/private_include/mdns_private.h

@@ -364,8 +364,7 @@ typedef struct {
         } srv_port;
         struct {
             mdns_srv_item_t * service;
-            uint8_t num_items;
-            mdns_txt_item_t * txt;
+            mdns_txt_linked_item_t * txt;
         } srv_txt_replace;
         struct {
             mdns_srv_item_t * service;