Fix bug where file descriptor 0 (aka stdin) was accidentally closed (#63

)
awslabs · Dec 31, 2021 · f850f5b · f850f5b
1 parent 7b64917
commit f850f5b
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Showing 2 changed files with 19 additions and 4 deletions.
diff --git a/source/linux/network.c b/source/linux/network.c
@@ -338,7 +338,7 @@ int get_network_config_and_transfer(struct aws_iotdevice_network_ifconfig *ifcon
         return AWS_OP_ERR;
     }
     int result = AWS_OP_ERR;
-    int fd = 0;
+    int fd = -1;
     struct ifaddrs *address_info = NULL;
     if (getifaddrs(&address_info)) {
         AWS_LOGF_ERROR(
@@ -408,8 +408,10 @@ int get_network_config_and_transfer(struct aws_iotdevice_network_ifconfig *ifcon
             goto cleanup;
         }
     next_interface:
-        close(fd);
-        fd = 0;
+        if (fd != -1) {
+            close(fd);
+            fd = -1;
+        }
         address = address->ifa_next;
     } /* while */
     result = AWS_OP_SUCCESS;
@@ -421,7 +423,7 @@ int get_network_config_and_transfer(struct aws_iotdevice_network_ifconfig *ifcon
     if (address_info) {
         freeifaddrs(address_info);
     }
-    if (fd) {
+    if (fd != -1) {
         close(fd);
     }
     return result;

diff --git a/tests/metrics_tests.c b/tests/metrics_tests.c
@@ -20,6 +20,11 @@
 #include <aws/mqtt/private/mqtt_client_test_helper.h>
 #include <aws/testing/aws_test_harness.h>
 
+#ifdef AWS_OS_LINUX
+#    include <errno.h>
+#    include <fcntl.h>
+#endif /* AWS_OS_LINUX */
+
 const char *TM_NUMBER = "TestMetricNumber";
 const char *TM_NUMBER_LIST = "TestMetricNumberList";
 const char *TM_STRING_LIST = "TestMetricStringList";
@@ -338,6 +343,14 @@ static int s_devicedefender_get_network_connections(struct aws_allocator *alloca
     AWS_ZERO_STRUCT(ifconfig);
     ASSERT_SUCCESS(get_network_config_and_transfer(&ifconfig, allocator));
 
+#ifdef AWS_OS_LINUX
+    /* Regression test: Check that get_network_config_and_transfer didn't
+     * accidentally close file descriptor 0 (aka stdin) */
+    errno = 0;
+    bool file_descriptor_0_is_closed = (fcntl(0, F_GETFD) == -1) && (errno != 0);
+    ASSERT_FALSE(file_descriptor_0_is_closed);
+#endif /* AWS_OS_LINUX */
+
     struct aws_array_list net_conns;
     AWS_ZERO_STRUCT(net_conns);
     aws_array_list_init_dynamic(&net_conns, allocator, 5, sizeof(struct aws_iotdevice_metric_net_connection));