From 5c522916f796aef7a9bf7a7b234bfb81232b52d0 Mon Sep 17 00:00:00 2001
From: Norman Maurer <norman_maurer@apple.com>
Date: Thu, 28 Jan 2021 15:15:21 +0100
Subject: [PATCH] Fix possible SEGV when using native dns resolver on macos
 (#10971)

Motivation:

We should add some more NULL checks to ensure we not SEGV in some cases

Modifications:

Add more NULL checks

Result:

More robust implementation
---
 .../src/main/c/netty_resolver_dns_macos.c     | 23 +++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/resolver-dns-native-macos/src/main/c/netty_resolver_dns_macos.c b/resolver-dns-native-macos/src/main/c/netty_resolver_dns_macos.c
index 699ad159e0..bc90c0e30e 100644
--- a/resolver-dns-native-macos/src/main/c/netty_resolver_dns_macos.c
+++ b/resolver-dns-native-macos/src/main/c/netty_resolver_dns_macos.c
@@ -45,7 +45,9 @@ static jmethodID dnsResolverMethodId = NULL;
 //     https://opensource.apple.com/tarballs/mDNSResponder/
 static jobjectArray netty_resolver_dns_macos_resolvers(JNIEnv* env, jclass clazz) {
     dns_config_t* config = dns_configuration_copy();
-
+    if (config == NULL) {
+        goto error;
+    }
     jobjectArray array = (*env)->NewObjectArray(env, config->n_resolver, dnsResolverClass, NULL);
     if (array == NULL) {
         goto error;
@@ -53,6 +55,9 @@ static jobjectArray netty_resolver_dns_macos_resolvers(JNIEnv* env, jclass clazz
 
     for (int i = 0; i < config->n_resolver; i++) {
         dns_resolver_t* resolver = config->resolver[i];
+        if (resolver == NULL) {
+            goto error;
+        }
         jstring domain = NULL;
 
         if (resolver->domain != NULL) {
@@ -68,7 +73,11 @@ static jobjectArray netty_resolver_dns_macos_resolvers(JNIEnv* env, jclass clazz
         }
 
         for (int a = 0; a < resolver->n_nameserver; a++) {
-            jbyteArray address = netty_unix_socket_createInetSocketAddressArray(env, (const struct sockaddr_storage *) resolver->nameserver[a]);
+            const struct sockaddr_storage* addr = (const struct sockaddr_storage *) resolver->nameserver[a];
+            if (addr == NULL) {
+                goto error;
+            }
+            jbyteArray address = netty_unix_socket_createInetSocketAddressArray(env, addr);
             if (address == NULL) {
                 netty_unix_errors_throwOutOfMemoryError(env);
                 goto error;
@@ -84,7 +93,11 @@ static jobjectArray netty_resolver_dns_macos_resolvers(JNIEnv* env, jclass clazz
         }
 
         for (int a = 0; a < resolver->n_search; a++) {
-            jstring search = (*env)->NewStringUTF(env, resolver->search[a]);
+            char* s = resolver->search[a];
+            if (s == NULL) {
+                goto error;
+            }
+            jstring search = (*env)->NewStringUTF(env, s);
             if (search == NULL) {
                 goto error;
             }
@@ -114,7 +127,9 @@ static jobjectArray netty_resolver_dns_macos_resolvers(JNIEnv* env, jclass clazz
     dns_configuration_free(config);
     return array;
 error:
-    dns_configuration_free(config);
+    if (config != NULL) {
+        dns_configuration_free(config);
+    }
     return NULL;
 }