raspberrypi · learmj · Jul 23, 2026 · Jul 23, 2026
diff --git a/rpiidp/src/device.cpp b/rpiidp/src/device.cpp
@@ -632,17 +632,12 @@ bool IDPdeviceWriter::WritePhysicalPartitions(std::string& reason)
      return false;
   }

-   if (device_->image_.device_storage.ptable_type == IDPptable_type::DOS) {
-      ret = parted.createPartitionTable("DOS", std::nullopt);
-   }
-   else {
-      std::optional<std::string> id = std::nullopt;
-      if (device_->image_.device_storage.ptable_id &&
-            !device_->image_.device_storage.ptable_id->empty()) {
-         id = device_->image_.device_storage.ptable_id;
-      }
-      ret = parted.createPartitionTable("GPT", id);
+   std::optional<std::string> id = std::nullopt;
+   if (device_->image_.device_storage.ptable_id &&
+         !device_->image_.device_storage.ptable_id->empty()) {
+      id = device_->image_.device_storage.ptable_id;
   }
+   ret = parted.createPartitionTable(type, id);

   if (!ret) {
      reason = "parted: failed to create " + type + " partition table on " + dev;

diff --git a/rpiidp/src/parser.cpp b/rpiidp/src/parser.cpp
@@ -459,29 +459,37 @@ bool IDPparser::parseIGv2(const Json::Value& json, const IDPversion& version, st
      return false;
   }

+   // Set partition table attrs
   size_t align = fromGIsz(str);
   if (align % (1024*1024) != 0) {
      ERR("Partition alignment must be a multiple of 1MB.");
      return false;
   }
   image_.device_storage.ptable_align = align;

-
   const Json::Value& ptable = json["layout"]["partitiontable"]["label"];

   if (ptable.asString() == "dos")
      image_.device_storage.ptable_type = IDPptable_type::DOS;
-   if (ptable.asString() == "gpt")
+   else if (ptable.asString() == "gpt")
      image_.device_storage.ptable_type = IDPptable_type::GPT;
+   else {
+      ERR("partitiontable: invalid 'label'");
+      return false;
+   }

-   if (image_.device_storage.ptable_type == IDPptable_type::GPT) {
-      const Json::Value& id = json["layout"]["partitiontable"]["id"];
-      if (id.isString() && !id.asString().empty())
-         image_.device_storage.ptable_id = id.asString();
-      else
-         image_.device_storage.ptable_id.reset();
+   const Json::Value& id = json["layout"]["partitiontable"]["id"];
+
+   if (!id.isNull() && !id.isString()) {
+      ERR("partitiontable: 'id' must be a string");
+      return false;
   }

+   if (id.isString() && !id.asString().empty())
+      image_.device_storage.ptable_id = id.asString();
+   else
+      image_.device_storage.ptable_id.reset();
+
   if (!checkPMAPCompat(json, str, error)) {
      ERR("PMAP compat check failed: " << error);
      return false;

diff --git a/rpiparted/src/rpiparted.cpp b/rpiparted/src/rpiparted.cpp
@@ -3,6 +3,7 @@
 #include <iostream>
 #include <algorithm>
 #include <cerrno>
+#include <cstdlib>
 #include <cstring>
 #include <unistd.h>

@@ -13,6 +14,23 @@
 #define ASSERT(cond, msg) do { if (!(cond)) { ERR(msg); std::abort(); } } while(0)


+namespace {
+   // Check a disklabel id string for being nothing but zeros. libfdisk
+   // does not reject an all-zero id.
+   bool is_zero_id(const std::string& id) {
+      std::string digits = id;
+      if (digits.size() > 1 && digits[0] == '0' && (digits[1] == 'x' || digits[1] == 'X')) {
+         digits.erase(0, 2);
+      }
+      digits.erase(std::remove(digits.begin(), digits.end(), '-'), digits.end());
+
+      return !digits.empty() && std::all_of(digits.begin(), digits.end(), [](unsigned char c) {
+         return c == '0';
+      });
+   }
+}
+
+
 FdiskContextDeleter::FdiskContextDeleter(bool* assigned)
    : assigned_(assigned) {}

@@ -106,14 +124,27 @@ bool RPIparted::createPartitionTable(const std::string& type, const std::optiona
   const char* label_type = (type_lower == "mbr") ? "dos" : type_lower.c_str();

   if (fdisk_create_disklabel(context_.get(), label_type) != 0) {
-      ERR("Failed to create label " << type);
+      ERR("Failed to create disk label for type " << type);
      return false;
   }

-   if (id && !id->empty() && \
-         fdisk_set_disklabel_id_from_string(context_.get(), id->c_str())) {
-      ERR("Invalid label ID " << id->c_str());
-      return false;
+   // Set disk label from user, else keep the one just generated
+   if (id && !id->empty()) {
+      if (fdisk_set_disklabel_id_from_string(context_.get(), id->c_str())) {
+         ERR("Invalid disk label (rejected) " << id->c_str() << " for type " << type);
+         return false;
+      }
+
+      // Reject an all-zero ID
+      char* applied_id = nullptr;
+      if (fdisk_get_disklabel_id(context_.get(), &applied_id) == 0 && applied_id) {
+         bool zero = is_zero_id(applied_id);
+         free(applied_id);
+         if (zero) {
+            ERR("Invalid disk label (rejected all-zero) " << id->c_str() << " for type " << type);
+            return false;
+         }
+      }
   }

   is_gpt_ = (type_lower == "gpt");