From: David Cermak <cermak@espressif.com>
Date: Tue, 29 Jan 2019 09:32:12 +0000 (+0100)
Subject: mdns: fixed crash on free undefined ptr after skipped strdup
X-Git-Tag: v3.2-beta3~28^2
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=43a722f0dec2a966df276e61d1329435c3654fe8;p=esp-idf

mdns: fixed crash on free undefined ptr after skipped strdup

Shortcircuit evaluation may cause skip of _mdns_strdup_check of any further question field, which after clear_rx_packet freed undefined memory.
Fixes https://ezredmine.espressif.cn:8765/issues/28465
---

diff --git a/components/mdns/mdns.c b/components/mdns/mdns.c
index f676b56d94..c77c9443fa 100644
--- a/components/mdns/mdns.c
+++ b/components/mdns/mdns.c
@@ -2487,15 +2487,19 @@ handle_error :
 }
 
 /**
- * @brief  Duplicate string or return NULL
+ * @brief  Duplicate string or return error
  */
-static char * _mdns_strdup_check(const char * in)
+static esp_err_t _mdns_strdup_check(char ** out, char * in)
 {
     if (in && in[0]) {
-        return strdup(in);
-    } else {
-        return NULL;
+        *out = strdup(in);
+        if (!*out) {
+            return ESP_FAIL;
+        }
+        return ESP_OK;
     }
+    *out = NULL;
+    return ESP_OK;
 }
 
 /**
@@ -2624,11 +2628,10 @@ void mdns_parse_packet(mdns_rx_packet_t * packet)
 
             question->unicast = unicast;
             question->type = type;
-            question->host = _mdns_strdup_check(name->host);
-            question->service = _mdns_strdup_check(name->service);
-            question->proto = _mdns_strdup_check(name->proto);
-            question->domain = _mdns_strdup_check(name->domain);
-            if (!question->host || !question->service || !question->proto || !question->domain) {
+            if (_mdns_strdup_check(&(question->host), name->host)
+              || _mdns_strdup_check(&(question->service), name->service)
+              || _mdns_strdup_check(&(question->proto), name->proto)
+              || _mdns_strdup_check(&(question->domain), name->domain)) {
                 goto clear_rx_packet;
             }
         }