Qt: Fix use-after-free pattern

This fixes crashes due to use of deallocated memory in:
- Export Packet Dissections
- Merge Capture Files
- Edit Packet Comment

Change-Id: I3dab8c0735eb5e642d6a4580d20bc3c81cf1345b
Reviewed-on: https://code.wireshark.org/review/10392
Petri-Dish: Stig Bjørlykke <stig@bjorlykke.org>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Stig Bjørlykke <stig@bjorlykke.org>

ui/qt/export_dissection_dialog.cpp

@@ -48,9 +48,9 @@ ExportDissectionDialog::ExportDissectionDialog(QWidget *parent, capture_file *ca
     QFileDialog(parent),
     export_type_(export_type),
     cap_file_(cap_file)
-  #if !defined(Q_OS_WIN)
+#if !defined(Q_OS_WIN)
     , save_bt_(NULL)
- #endif /* Q_OS_WIN */
+#endif /* Q_OS_WIN */
 {
 #if !defined(Q_OS_WIN)
     QDialogButtonBox *button_box = findChild<QDialogButtonBox *>();
@@ -86,6 +86,7 @@ ExportDissectionDialog::ExportDissectionDialog(QWidget *parent, capture_file *ca
     fd_grid->addItem(new QSpacerItem(1, 1), last_row, 0);
     fd_grid->addLayout(h_box, last_row, 1);
 
+    print_args_.file = NULL;
     /* Init the export range */
     packet_range_init(&print_args_.range, cap_file_);
     /* Default to displayed packets */
@@ -120,6 +121,9 @@ ExportDissectionDialog::ExportDissectionDialog(QWidget *parent, capture_file *ca
 
 ExportDissectionDialog::~ExportDissectionDialog()
 {
+#if !defined(Q_OS_WIN)
+    g_free(print_args_.file);
+#endif
 }
 
 int ExportDissectionDialog::exec()
@@ -137,7 +141,7 @@ int ExportDissectionDialog::exec()
 
         /* Fill in our print (and export) args */
 
-        print_args_.file                = file_name.toUtf8().data();
+        print_args_.file                = qstring_strdup(file_name);
         print_args_.format              = PR_FMT_TEXT;
         print_args_.to_file             = TRUE;
         print_args_.cmd                 = NULL;

ui/qt/import_text_dialog.cpp

@@ -41,6 +41,7 @@
 
 #include <ui_import_text_dialog.h>
 #include "wireshark_application.h"
+#include "qt_ui_utils.h"
 
 #include <QFileDialog>
 #include <QDebug>
@@ -213,7 +214,7 @@ int ImportTextDialog::exec() {
         return result();
     }
 
-    import_info_.import_text_filename = g_strdup(ti_ui_->textFileLineEdit->text().toUtf8().data());
+    import_info_.import_text_filename = qstring_strdup(ti_ui_->textFileLineEdit->text());
     import_info_.import_text_file = ws_fopen(import_info_.import_text_filename, "rb");
     if (!import_info_.import_text_file) {
         open_failure_alert_box(import_info_.import_text_filename, errno, FALSE);
@@ -227,7 +228,7 @@ int ImportTextDialog::exec() {
         ti_ui_->octalOffsetButton->isChecked()   ? OFFSET_OCT :
         OFFSET_NONE;
     import_info_.date_timestamp = ti_ui_->dateTimeLineEdit->text().length() > 0;
-    import_info_.date_timestamp_format = g_strdup(ti_ui_->dateTimeLineEdit->text().toUtf8().data());
+    import_info_.date_timestamp_format = qstring_strdup(ti_ui_->dateTimeLineEdit->text());
 
     encap_val = ti_ui_->encapComboBox->itemData(ti_ui_->encapComboBox->currentIndex());
     import_info_.dummy_header_type = HEADER_NONE;

ui/qt/main_window.cpp

@@ -911,21 +911,24 @@ void MainWindow::mergeCaptureFile()
         tmpname = NULL;
         if (merge_dlg.mergeType() == 0) {
             /* chronological order */
-            in_filenames[0] = capture_file_.capFile()->filename;
-            in_filenames[1] = file_name.toUtf8().data();
+            in_filenames[0] = g_strdup(capture_file_.capFile()->filename);
+            in_filenames[1] = qstring_strdup(file_name);
             merge_status = cf_merge_files(&tmpname, 2, in_filenames, file_type, FALSE);
         } else if (merge_dlg.mergeType() <= 0) {
             /* prepend file */
-            in_filenames[0] = file_name.toUtf8().data();
-            in_filenames[1] = capture_file_.capFile()->filename;
+            in_filenames[0] = qstring_strdup(file_name);
+            in_filenames[1] = g_strdup(capture_file_.capFile()->filename);
             merge_status = cf_merge_files(&tmpname, 2, in_filenames, file_type, TRUE);
         } else {
             /* append file */
-            in_filenames[0] = capture_file_.capFile()->filename;
-            in_filenames[1] = file_name.toUtf8().data();
+            in_filenames[0] = g_strdup(capture_file_.capFile()->filename);
+            in_filenames[1] = qstring_strdup(file_name);
             merge_status = cf_merge_files(&tmpname, 2, in_filenames, file_type, TRUE);
         }
 
+        g_free(in_filenames[0]);
+        g_free(in_filenames[1]);
+
         if (merge_status != CF_OK) {
             if (rfcode != NULL)
                 dfilter_free(rfcode);

ui/qt/packet_list.cpp

@@ -888,7 +888,7 @@ void PacketList::setPacketComment(QString new_comment)
 {
     int row = currentIndex().row();
     frame_data *fdata;
-    gchar *new_packet_comment = new_comment.toUtf8().data();
+    gchar *new_packet_comment;
 
     if (!cap_file_ || !packet_list_model_) return;
 
@@ -899,9 +899,12 @@ void PacketList::setPacketComment(QString new_comment)
     /* Check if we are clearing the comment */
     if(new_comment.isEmpty()) {
         new_packet_comment = NULL;
+    } else {
+        new_packet_comment = qstring_strdup(new_comment);
     }
 
     cf_set_user_packet_comment(cap_file_, fdata, new_packet_comment);
+    g_free(new_packet_comment);
 
     redrawVisiblePackets();
 }