S7Comm: Fix invalid UTF-8 value string chars

Fixes #18533.

5 files changed, 27 insertions, 5 deletions

diff --git a/epan/dissectors/packet-s7comm.c b/epan/dissectors/packet-s7comm.c
index 576f640605..d2c308eafd 100644
--- a/epan/dissectors/packet-s7comm.c
+++ b/epan/dissectors/packet-s7comm.c
@@ -3308,7 +3308,7 @@ s7comm_decode_pi_service(tvbuff_t *tvb,
                     col_append_str(pinfo->cinfo, COL_INFO, ", ");
                 }
                 itemadd = proto_tree_add_item(file_tree, hf_s7comm_data_blockcontrol_dest_filesys, tvb, paramoffset, 1, ENC_ASCII);
-                proto_item_append_text(itemadd, " (%s)", val_to_str(tvb_get_guint8(tvb, paramoffset), blocktype_attribute2_names, "Unknown filesys: %c"));
+                proto_item_append_text(itemadd, " (%s)", char_val_to_str(tvb_get_guint8(tvb, paramoffset), blocktype_attribute2_names, "Unknown filesys"));
                 paramoffset += 1;
             }
             col_append_str(pinfo->cinfo, COL_INFO, ")");
@@ -3667,7 +3667,7 @@ s7comm_decode_plc_controls_filename(tvbuff_t *tvb,
                 col_append_str(pinfo->cinfo, COL_INFO, "NaN]");
             }
             itemadd = proto_tree_add_item(file_tree, hf_s7comm_data_blockcontrol_dest_filesys, tvb, offset, 1, ENC_ASCII);
-            proto_item_append_text(itemadd, " (%s)", val_to_str(tvb_get_guint8(tvb, offset), blocktype_attribute2_names, "Unknown filesys: %c"));
+            proto_item_append_text(itemadd, " (%s)", char_val_to_str(tvb_get_guint8(tvb, offset), blocktype_attribute2_names, "Unknown filesys"));
             offset += 1;
         }
     }
@@ -6221,7 +6221,7 @@ s7comm_decode_ud_block_subfunc(tvbuff_t *tvb,
                     }
                     offset += 5;
                     itemadd = proto_tree_add_item(data_tree, hf_s7comm_ud_blockinfo_filesys, tvb, offset, 1, ENC_ASCII);
-                    proto_item_append_text(itemadd, " (%s)", val_to_str(tvb_get_guint8(tvb, offset), blocktype_attribute2_names, "Unknown filesys: %c"));
+                    proto_item_append_text(itemadd, " (%s)", char_val_to_str(tvb_get_guint8(tvb, offset), blocktype_attribute2_names, "Unknown filesys"));
                     offset += 1;
                 }
                 know_data = TRUE;
diff --git a/epan/proto.c b/epan/proto.c
index 8c37095c7e..43ecd038ff 100644
--- a/epan/proto.c
+++ b/epan/proto.c
@@ -237,7 +237,6 @@ static void fill_label_number64(field_info *fi, gchar *label_str, gboolean is_si
 static size_t fill_display_label_float(field_info *fi, gchar *label_str);
 static void fill_label_float(field_info *fi, gchar *label_str);
 
-static const char *hfinfo_char_value_format_display(int display, char buf[7], guint32 value);
 static const char *hfinfo_number_value_format_display(const header_field_info *hfinfo, int display, char buf[32], guint32 value);
 static const char *hfinfo_number_value_format_display64(const header_field_info *hfinfo, int display, char buf[48], guint64 value);
 static const char *hfinfo_char_vals_format(const header_field_info *hfinfo, char buf[32], guint32 value);
@@ -10103,7 +10102,7 @@ hfinfo_hex_digits(const header_field_info *hfinfo)
 	return (bitwidth + 3) / 4;
 }
 
-static const char *
+const char *
 hfinfo_char_value_format_display(int display, char buf[7], guint32 value)
 {
 	char *ptr = &buf[6];
diff --git a/epan/proto.h b/epan/proto.h
index ef58a9666d..475fdb37ff 100644
--- a/epan/proto.h
+++ b/epan/proto.h
@@ -3357,6 +3357,9 @@ proto_custom_set(proto_tree* tree, GSList *field_id,
 
 /** @} */
 
+const char *
+hfinfo_char_value_format_display(int display, char buf[7], guint32 value);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */
diff --git a/epan/value_string.c b/epan/value_string.c
index 841eed789f..82eb833ff4 100644
--- a/epan/value_string.c
+++ b/epan/value_string.c
@@ -106,6 +106,22 @@ try_val_to_str(const guint32 val, const value_string *vs)
     return try_val_to_str_idx(val, vs, &ignore_me);
 }
 
+const gchar *
+char_val_to_str(char val, const value_string *vs, const char *msg)
+{
+    const gchar *ret;
+    char buf[7];
+
+    DISSECTOR_ASSERT(msg != NULL);
+
+    ret = try_val_to_str(val, vs);
+    if (ret != NULL)
+        return ret;
+
+    return wmem_strdup_printf(wmem_packet_scope(), "%s: %s",
+            msg, hfinfo_char_value_format_display(BASE_HEX, buf, val));
+}
+
 /* 64-BIT VALUE STRING */
 
 const gchar *
diff --git a/epan/value_string.h b/epan/value_string.h
index a8c3a31743..c0ee2551b7 100644
--- a/epan/value_string.h
+++ b/epan/value_string.h
@@ -124,6 +124,10 @@ WS_DLL_PUBLIC
 const gchar *
 try_val_to_str_idx(const guint32 val, const value_string *vs, gint *idx);
 
+WS_DLL_PUBLIC
+const gchar *
+char_val_to_str(char val, const value_string *vs, const char *msg);
+
 /* 64-BIT VALUE TO STRING MATCHING */
 
 typedef struct _val64_string {