ipa: Use FileDescriptor instead of int in layers above IPC payload

Regarding (de)serialization in isolated IPA calls, we have four layers:
- struct
- byte vector + fd vector
- IPCMessage
- IPC payload

The proxy handles the upper three layers (with help from the
IPADataSerializer), and passes an IPCMessage to the IPC mechanism
(implemented as an IPCPipe), which sends an IPC payload to its worker
counterpart.

When a FileDescriptor is involved, previously it was only a
FileDescriptor in the first layer; in the lower three it was an int. To
reduce the risk of potential fd leaks in the future, keep the
FileDescriptor as-is throughout the upper three layers. Only the IPC
mechanism will deal with ints, if it so wishes, when it does the actual
IPC. IPCPipeUnixSocket does deal with ints for sending fds, so the
conversion between IPCMessage and IPCUnixSocket::Payload converts
between FileDescriptor and int.

Additionally, change the data portion of the serialized form of
FileDescriptor to a 32-bit unsigned integer, for alightnment purposes
and in preparation for conversion to an index into the fd array.

Also update the deserializer of FrameBuffer::Plane accordingly.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Tested-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>

9 files changed, 108 insertions, 93 deletions

diff --git a/include/libcamera/internal/ipa_data_serializer.h b/include/libcamera/internal/ipa_data_serializer.h
index 519093bd..4353e07b 100644
--- a/include/libcamera/internal/ipa_data_serializer.h
+++ b/include/libcamera/internal/ipa_data_serializer.h
@@ -66,7 +66,7 @@ template<typename T>
 class IPADataSerializer
 {
 public:
-	static std::tuple<std::vector<uint8_t>, std::vector<int32_t>>
+	static std::tuple<std::vector<uint8_t>, std::vector<FileDescriptor>>
 	serialize(const T &data, ControlSerializer *cs = nullptr);
 
 	static T deserialize(const std::vector<uint8_t> &data,
@@ -76,12 +76,12 @@ public:
 			     ControlSerializer *cs = nullptr);
 
 	static T deserialize(const std::vector<uint8_t> &data,
-			     const std::vector<int32_t> &fds,
+			     const std::vector<FileDescriptor> &fds,
 			     ControlSerializer *cs = nullptr);
 	static T deserialize(std::vector<uint8_t>::const_iterator dataBegin,
 			     std::vector<uint8_t>::const_iterator dataEnd,
-			     std::vector<int32_t>::const_iterator fdsBegin,
-			     std::vector<int32_t>::const_iterator fdsEnd,
+			     std::vector<FileDescriptor>::const_iterator fdsBegin,
+			     std::vector<FileDescriptor>::const_iterator fdsEnd,
 			     ControlSerializer *cs = nullptr);
 };
 
@@ -104,11 +104,11 @@ template<typename V>
 class IPADataSerializer<std::vector<V>>
 {
 public:
-	static std::tuple<std::vector<uint8_t>, std::vector<int32_t>>
+	static std::tuple<std::vector<uint8_t>, std::vector<FileDescriptor>>
 	serialize(const std::vector<V> &data, ControlSerializer *cs = nullptr)
 	{
 		std::vector<uint8_t> dataVec;
-		std::vector<int32_t> fdsVec;
+		std::vector<FileDescriptor> fdsVec;
 
 		/* Serialize the length. */
 		uint32_t vecLen = data.size();
@@ -117,7 +117,7 @@ public:
 		/* Serialize the members. */
 		for (auto const &it : data) {
 			std::vector<uint8_t> dvec;
-			std::vector<int32_t> fvec;
+			std::vector<FileDescriptor> fvec;
 
 			std::tie(dvec, fvec) =
 				IPADataSerializer<V>::serialize(it, cs);
@@ -141,11 +141,11 @@ public:
 					  std::vector<uint8_t>::const_iterator dataEnd,
 					  ControlSerializer *cs = nullptr)
 	{
-		std::vector<int32_t> fds;
+		std::vector<FileDescriptor> fds;
 		return deserialize(dataBegin, dataEnd, fds.cbegin(), fds.end(), cs);
 	}
 
-	static std::vector<V> deserialize(std::vector<uint8_t> &data, std::vector<int32_t> &fds,
+	static std::vector<V> deserialize(std::vector<uint8_t> &data, std::vector<FileDescriptor> &fds,
 					  ControlSerializer *cs = nullptr)
 	{
 		return deserialize(data.cbegin(), data.end(), fds.cbegin(), fds.end(), cs);
@@ -153,15 +153,15 @@ public:
 
 	static std::vector<V> deserialize(std::vector<uint8_t>::const_iterator dataBegin,
 					  std::vector<uint8_t>::const_iterator dataEnd,
-					  std::vector<int32_t>::const_iterator fdsBegin,
-					  [[maybe_unused]] std::vector<int32_t>::const_iterator fdsEnd,
+					  std::vector<FileDescriptor>::const_iterator fdsBegin,
+					  [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsEnd,
 					  ControlSerializer *cs = nullptr)
 	{
 		uint32_t vecLen = readPOD<uint32_t>(dataBegin, 0, dataEnd);
 		std::vector<V> ret(vecLen);
 
 		std::vector<uint8_t>::const_iterator dataIter = dataBegin + 4;
-		std::vector<int32_t>::const_iterator fdIter = fdsBegin;
+		std::vector<FileDescriptor>::const_iterator fdIter = fdsBegin;
 		for (uint32_t i = 0; i < vecLen; i++) {
 			uint32_t sizeofData = readPOD<uint32_t>(dataIter, 0, dataEnd);
 			uint32_t sizeofFds  = readPOD<uint32_t>(dataIter, 4, dataEnd);
@@ -201,11 +201,11 @@ template<typename K, typename V>
 class IPADataSerializer<std::map<K, V>>
 {
 public:
-	static std::tuple<std::vector<uint8_t>, std::vector<int32_t>>
+	static std::tuple<std::vector<uint8_t>, std::vector<FileDescriptor>>
 	serialize(const std::map<K, V> &data, ControlSerializer *cs = nullptr)
 	{
 		std::vector<uint8_t> dataVec;
-		std::vector<int32_t> fdsVec;
+		std::vector<FileDescriptor> fdsVec;
 
 		/* Serialize the length. */
 		uint32_t mapLen = data.size();
@@ -214,7 +214,7 @@ public:
 		/* Serialize the members. */
 		for (auto const &it : data) {
 			std::vector<uint8_t> dvec;
-			std::vector<int32_t> fvec;
+			std::vector<FileDescriptor> fvec;
 
 			std::tie(dvec, fvec) =
 				IPADataSerializer<K>::serialize(it.first, cs);
@@ -247,11 +247,11 @@ public:
 					  std::vector<uint8_t>::const_iterator dataEnd,
 					  ControlSerializer *cs = nullptr)
 	{
-		std::vector<int32_t> fds;
+		std::vector<FileDescriptor> fds;
 		return deserialize(dataBegin, dataEnd, fds.cbegin(), fds.end(), cs);
 	}
 
-	static std::map<K, V> deserialize(std::vector<uint8_t> &data, std::vector<int32_t> &fds,
+	static std::map<K, V> deserialize(std::vector<uint8_t> &data, std::vector<FileDescriptor> &fds,
 					  ControlSerializer *cs = nullptr)
 	{
 		return deserialize(data.cbegin(), data.end(), fds.cbegin(), fds.end(), cs);
@@ -259,8 +259,8 @@ public:
 
 	static std::map<K, V> deserialize(std::vector<uint8_t>::const_iterator dataBegin,
 					  std::vector<uint8_t>::const_iterator dataEnd,
-					  std::vector<int32_t>::const_iterator fdsBegin,
-					  [[maybe_unused]] std::vector<int32_t>::const_iterator fdsEnd,
+					  std::vector<FileDescriptor>::const_iterator fdsBegin,
+					  [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsEnd,
 					  ControlSerializer *cs = nullptr)
 	{
 		std::map<K, V> ret;
@@ -268,7 +268,7 @@ public:
 		uint32_t mapLen = readPOD<uint32_t>(dataBegin, 0, dataEnd);
 
 		std::vector<uint8_t>::const_iterator dataIter = dataBegin + 4;
-		std::vector<int32_t>::const_iterator fdIter = fdsBegin;
+		std::vector<FileDescriptor>::const_iterator fdIter = fdsBegin;
 		for (uint32_t i = 0; i < mapLen; i++) {
 			uint32_t sizeofData = readPOD<uint32_t>(dataIter, 0, dataEnd);
 			uint32_t sizeofFds  = readPOD<uint32_t>(dataIter, 4, dataEnd);
diff --git a/include/libcamera/internal/ipc_pipe.h b/include/libcamera/internal/ipc_pipe.h
index e58de340..52cc8fa3 100644
--- a/include/libcamera/internal/ipc_pipe.h
+++ b/include/libcamera/internal/ipc_pipe.h
@@ -11,6 +11,8 @@
 
 #include <libcamera/base/signal.h>
 
+#include <libcamera/file_descriptor.h>
+
 #include "libcamera/internal/ipc_unixsocket.h"
 
 namespace libcamera {
@@ -26,23 +28,23 @@ public:
 	IPCMessage();
 	IPCMessage(uint32_t cmd);
 	IPCMessage(const Header &header);
-	IPCMessage(const IPCUnixSocket::Payload &payload);
+	IPCMessage(IPCUnixSocket::Payload &payload);
 
 	IPCUnixSocket::Payload payload() const;
 
 	Header &header() { return header_; }
 	std::vector<uint8_t> &data() { return data_; }
-	std::vector<int32_t> &fds() { return fds_; }
+	std::vector<FileDescriptor> &fds() { return fds_; }
 
 	const Header &header() const { return header_; }
 	const std::vector<uint8_t> &data() const { return data_; }
-	const std::vector<int32_t> &fds() const { return fds_; }
+	const std::vector<FileDescriptor> &fds() const { return fds_; }
 
 private:
 	Header header_;
 
 	std::vector<uint8_t> data_;
-	std::vector<int32_t> fds_;
+	std::vector<FileDescriptor> fds_;
 };
 
 class IPCPipe
diff --git a/src/libcamera/ipa_data_serializer.cpp b/src/libcamera/ipa_data_serializer.cpp
index fb941e6b..5b183c70 100644
--- a/src/libcamera/ipa_data_serializer.cpp
+++ b/src/libcamera/ipa_data_serializer.cpp
@@ -7,6 +7,8 @@
 
 #include "libcamera/internal/ipa_data_serializer.h"
 
+#include <unistd.h>
+
 #include <libcamera/base/log.h>
 
 /**
@@ -141,7 +143,7 @@ namespace {
 /**
  * \fn template<typename T> IPADataSerializer<T>::deserialize(
  * 	const std::vector<uint8_t> &data,
- * 	const std::vector<int32_t> &fds,
+ * 	const std::vector<FileDescriptor> &fds,
  * 	ControlSerializer *cs = nullptr)
  * \brief Deserialize byte vector and fd vector into an object
  * \tparam T Type of object to deserialize to
@@ -162,8 +164,8 @@ namespace {
  * \fn template<typename T> IPADataSerializer::deserialize(
  * 	std::vector<uint8_t>::const_iterator dataBegin,
  * 	std::vector<uint8_t>::const_iterator dataEnd,
- * 	std::vector<int32_t>::const_iterator fdsBegin,
- * 	std::vector<int32_t>::const_iterator fdsEnd,
+ * 	std::vector<FileDescriptor>::const_iterator fdsBegin,
+ * 	std::vector<FileDescriptor>::const_iterator fdsEnd,
  * 	ControlSerializer *cs = nullptr)
  * \brief Deserialize byte vector and fd vector into an object
  * \tparam T Type of object to deserialize to
@@ -187,7 +189,7 @@ namespace {
 #define DEFINE_POD_SERIALIZER(type)					\
 									\
 template<>								\
-std::tuple<std::vector<uint8_t>, std::vector<int32_t>>			\
+std::tuple<std::vector<uint8_t>, std::vector<FileDescriptor>>		\
 IPADataSerializer<type>::serialize(const type &data,			\
 				  [[maybe_unused]] ControlSerializer *cs) \
 {									\
@@ -215,7 +217,7 @@ type IPADataSerializer<type>::deserialize(const std::vector<uint8_t> &data, \
 									\
 template<>								\
 type IPADataSerializer<type>::deserialize(const std::vector<uint8_t> &data, \
-					  [[maybe_unused]] const std::vector<int32_t> &fds, \
+					  [[maybe_unused]] const std::vector<FileDescriptor> &fds, \
 					  ControlSerializer *cs)	\
 {									\
 	return deserialize(data.cbegin(), data.end(), cs);		\
@@ -224,8 +226,8 @@ type IPADataSerializer<type>::deserialize(const std::vector<uint8_t> &data, \
 template<>								\
 type IPADataSerializer<type>::deserialize(std::vector<uint8_t>::const_iterator dataBegin, \
 					  std::vector<uint8_t>::const_iterator dataEnd, \
-					  [[maybe_unused]] std::vector<int32_t>::const_iterator fdsBegin, \
-					  [[maybe_unused]] std::vector<int32_t>::const_iterator fdsEnd, \
+					  [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsBegin, \
+					  [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsEnd, \
 					  ControlSerializer *cs)	\
 {									\
 	return deserialize(dataBegin, dataEnd, cs);			\
@@ -249,7 +251,7 @@ DEFINE_POD_SERIALIZER(double)
  * function parameter serdes).
  */
 template<>
-std::tuple<std::vector<uint8_t>, std::vector<int32_t>>
+std::tuple<std::vector<uint8_t>, std::vector<FileDescriptor>>
 IPADataSerializer<std::string>::serialize(const std::string &data,
 					  [[maybe_unused]] ControlSerializer *cs)
 {
@@ -276,7 +278,7 @@ IPADataSerializer<std::string>::deserialize(std::vector<uint8_t>::const_iterator
 template<>
 std::string
 IPADataSerializer<std::string>::deserialize(const std::vector<uint8_t> &data,
-					    [[maybe_unused]] const std::vector<int32_t> &fds,
+					    [[maybe_unused]] const std::vector<FileDescriptor> &fds,
 					    [[maybe_unused]] ControlSerializer *cs)
 {
 	return { data.cbegin(), data.cend() };
@@ -286,8 +288,8 @@ template<>
 std::string
 IPADataSerializer<std::string>::deserialize(std::vector<uint8_t>::const_iterator dataBegin,
 					    std::vector<uint8_t>::const_iterator dataEnd,
-					    [[maybe_unused]] std::vector<int32_t>::const_iterator fdsBegin,
-					    [[maybe_unused]] std::vector<int32_t>::const_iterator fdsEnd,
+					    [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsBegin,
+					    [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsEnd,
 					    [[maybe_unused]] ControlSerializer *cs)
 {
 	return { dataBegin, dataEnd };
@@ -305,7 +307,7 @@ IPADataSerializer<std::string>::deserialize(std::vector<uint8_t>::const_iterator
  * be used. The serialized ControlInfoMap will have zero length.
  */
 template<>
-std::tuple<std::vector<uint8_t>, std::vector<int32_t>>
+std::tuple<std::vector<uint8_t>, std::vector<FileDescriptor>>
 IPADataSerializer<ControlList>::serialize(const ControlList &data, ControlSerializer *cs)
 {
 	if (!cs)
@@ -405,7 +407,7 @@ IPADataSerializer<ControlList>::deserialize(const std::vector<uint8_t> &data,
 template<>
 ControlList
 IPADataSerializer<ControlList>::deserialize(const std::vector<uint8_t> &data,
-					    [[maybe_unused]] const std::vector<int32_t> &fds,
+					    [[maybe_unused]] const std::vector<FileDescriptor> &fds,
 					    ControlSerializer *cs)
 {
 	return deserialize(data.cbegin(), data.end(), cs);
@@ -415,8 +417,8 @@ template<>
 ControlList
 IPADataSerializer<ControlList>::deserialize(std::vector<uint8_t>::const_iterator dataBegin,
 					    std::vector<uint8_t>::const_iterator dataEnd,
-					    [[maybe_unused]] std::vector<int32_t>::const_iterator fdsBegin,
-					    [[maybe_unused]] std::vector<int32_t>::const_iterator fdsEnd,
+					    [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsBegin,
+					    [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsEnd,
 					    ControlSerializer *cs)
 {
 	return deserialize(dataBegin, dataEnd, cs);
@@ -429,7 +431,7 @@ IPADataSerializer<ControlList>::deserialize(std::vector<uint8_t>::const_iterator
  * X bytes - Serialized ControlInfoMap (using ControlSerializer)
  */
 template<>
-std::tuple<std::vector<uint8_t>, std::vector<int32_t>>
+std::tuple<std::vector<uint8_t>, std::vector<FileDescriptor>>
 IPADataSerializer<ControlInfoMap>::serialize(const ControlInfoMap &map,
 					     ControlSerializer *cs)
 {
@@ -491,7 +493,7 @@ IPADataSerializer<ControlInfoMap>::deserialize(const std::vector<uint8_t> &data,
 template<>
 ControlInfoMap
 IPADataSerializer<ControlInfoMap>::deserialize(const std::vector<uint8_t> &data,
-					       [[maybe_unused]] const std::vector<int32_t> &fds,
+					       [[maybe_unused]] const std::vector<FileDescriptor> &fds,
 					       ControlSerializer *cs)
 {
 	return deserialize(data.cbegin(), data.end(), cs);
@@ -501,15 +503,15 @@ template<>
 ControlInfoMap
 IPADataSerializer<ControlInfoMap>::deserialize(std::vector<uint8_t>::const_iterator dataBegin,
 					       std::vector<uint8_t>::const_iterator dataEnd,
-					       [[maybe_unused]] std::vector<int32_t>::const_iterator fdsBegin,
-					       [[maybe_unused]] std::vector<int32_t>::const_iterator fdsEnd,
+					       [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsBegin,
+					       [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsEnd,
 					       ControlSerializer *cs)
 {
 	return deserialize(dataBegin, dataEnd, cs);
 }
 
 /*
- * FileDescriptors are serialized into a single byte that tells if the
+ * FileDescriptors are serialized into four bytes that tells if the
  * FileDescriptor is valid or not. If it is valid, then for serialization
  * the fd will be written to the fd vector, or for deserialization the
  * fd vector const_iterator will be valid.
@@ -517,42 +519,47 @@ IPADataSerializer<ControlInfoMap>::deserialize(std::vector<uint8_t>::const_itera
  * This validity is necessary so that we don't send -1 fd over sendmsg(). It
  * also allows us to simply send the entire fd vector into the deserializer
  * and it will be recursively consumed as necessary.
- *
- * \todo Consider serializing the FileDescriptor in 4 bytes to ensure
- * 32-bit alignment of all serialized data
  */
 template<>
-std::tuple<std::vector<uint8_t>, std::vector<int32_t>>
+std::tuple<std::vector<uint8_t>, std::vector<FileDescriptor>>
 IPADataSerializer<FileDescriptor>::serialize(const FileDescriptor &data,
 					     [[maybe_unused]] ControlSerializer *cs)
 {
-	std::vector<uint8_t> dataVec = { data.isValid() };
-	std::vector<int32_t> fdVec;
+	std::vector<uint8_t> dataVec;
+	std::vector<FileDescriptor> fdVec;
+
+	/*
+	 * Store as uint32_t to prepare for conversion from validity flag
+	 * to index, and for alignment.
+	 */
+	appendPOD<uint32_t>(dataVec, data.isValid());
+
 	if (data.isValid())
-		fdVec.push_back(data.fd());
+		fdVec.push_back(data);
+
 
 	return { dataVec, fdVec };
 }
 
 template<>
-FileDescriptor IPADataSerializer<FileDescriptor>::deserialize(std::vector<uint8_t>::const_iterator dataBegin,
-							      std::vector<uint8_t>::const_iterator dataEnd,
-							      std::vector<int32_t>::const_iterator fdsBegin,
-							      std::vector<int32_t>::const_iterator fdsEnd,
+FileDescriptor IPADataSerializer<FileDescriptor>::deserialize([[maybe_unused]] std::vector<uint8_t>::const_iterator dataBegin,
+							      [[maybe_unused]] std::vector<uint8_t>::const_iterator dataEnd,
+							      std::vector<FileDescriptor>::const_iterator fdsBegin,
+							      std::vector<FileDescriptor>::const_iterator fdsEnd,
 							      [[maybe_unused]] ControlSerializer *cs)
 {
-	ASSERT(std::distance(dataBegin, dataEnd) >= 1);
+	ASSERT(std::distance(dataBegin, dataEnd) >= 4);
 
-	bool valid = !!(*dataBegin);
+	uint32_t valid = readPOD<uint32_t>(dataBegin, 0, dataEnd);
 
 	ASSERT(!(valid && std::distance(fdsBegin, fdsEnd) < 1));
 
-	return valid ? FileDescriptor(*fdsBegin) : FileDescriptor();
+	return valid ? *fdsBegin : FileDescriptor();
 }
 
 template<>
 FileDescriptor IPADataSerializer<FileDescriptor>::deserialize(const std::vector<uint8_t> &data,
-							      const std::vector<int32_t> &fds,
+							      const std::vector<FileDescriptor> &fds,
 							      [[maybe_unused]] ControlSerializer *cs)
 {
 	return deserialize(data.cbegin(), data.end(), fds.cbegin(), fds.end());
@@ -561,19 +568,19 @@ FileDescriptor IPADataSerializer<FileDescriptor>::deserialize(const std::vector<
 /*
  * FrameBuffer::Plane is serialized as:
  *
- * 1 byte  - FileDescriptor
+ * 4 byte  - FileDescriptor
  * 4 bytes - uint32_t Length
  */
 template<>
-std::tuple<std::vector<uint8_t>, std::vector<int32_t>>
+std::tuple<std::vector<uint8_t>, std::vector<FileDescriptor>>
 IPADataSerializer<FrameBuffer::Plane>::serialize(const FrameBuffer::Plane &data,
 						 [[maybe_unused]] ControlSerializer *cs)
 {
 	std::vector<uint8_t> dataVec;
-	std::vector<int32_t> fdsVec;
+	std::vector<FileDescriptor> fdsVec;
 
 	std::vector<uint8_t> fdBuf;
-	std::vector<int32_t> fdFds;
+	std::vector<FileDescriptor> fdFds;
 	std::tie(fdBuf, fdFds) =
 		IPADataSerializer<FileDescriptor>::serialize(data.fd);
 	dataVec.insert(dataVec.end(), fdBuf.begin(), fdBuf.end());
@@ -588,15 +595,15 @@ template<>
 FrameBuffer::Plane
 IPADataSerializer<FrameBuffer::Plane>::deserialize(std::vector<uint8_t>::const_iterator dataBegin,
 						   std::vector<uint8_t>::const_iterator dataEnd,
-						   std::vector<int32_t>::const_iterator fdsBegin,
-						   [[maybe_unused]] std::vector<int32_t>::const_iterator fdsEnd,
+						   std::vector<FileDescriptor>::const_iterator fdsBegin,
+						   [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsEnd,
 						   [[maybe_unused]] ControlSerializer *cs)
 {
 	FrameBuffer::Plane ret;
 
-	ret.fd = IPADataSerializer<FileDescriptor>::deserialize(dataBegin, dataBegin + 1,
+	ret.fd = IPADataSerializer<FileDescriptor>::deserialize(dataBegin, dataBegin + 4,
 								fdsBegin, fdsBegin + 1);
-	ret.length = readPOD<uint32_t>(dataBegin, 1, dataEnd);
+	ret.length = readPOD<uint32_t>(dataBegin, 4, dataEnd);
 
 	return ret;
 }
@@ -604,7 +611,7 @@ IPADataSerializer<FrameBuffer::Plane>::deserialize(std::vector<uint8_t>::const_i
 template<>
 FrameBuffer::Plane
 IPADataSerializer<FrameBuffer::Plane>::deserialize(const std::vector<uint8_t> &data,
-						   const std::vector<int32_t> &fds,
+						   const std::vector<FileDescriptor> &fds,
 						   ControlSerializer *cs)
 {
 	return deserialize(data.cbegin(), data.end(), fds.cbegin(), fds.end(), cs);
diff --git a/src/libcamera/ipc_pipe.cpp b/src/libcamera/ipc_pipe.cpp
index 28e20e03..84136a82 100644
--- a/src/libcamera/ipc_pipe.cpp
+++ b/src/libcamera/ipc_pipe.cpp
@@ -77,13 +77,17 @@ IPCMessage::IPCMessage(const Header &header)
  *
  * This essentially converts an IPCUnixSocket payload into an IPCMessage.
  * The header is extracted from the payload into the IPCMessage's header field.
+ *
+ * If the IPCUnixSocket payload had any valid file descriptors, then they will
+ * all be invalidated.
  */
-IPCMessage::IPCMessage(const IPCUnixSocket::Payload &payload)
+IPCMessage::IPCMessage(IPCUnixSocket::Payload &payload)
 {
 	memcpy(&header_, payload.data.data(), sizeof(header_));
 	data_ = std::vector<uint8_t>(payload.data.begin() + sizeof(header_),
 				     payload.data.end());
-	fds_ = payload.fds;
+	for (int32_t &fd : payload.fds)
+		fds_.push_back(FileDescriptor(std::move(fd)));
 }
 
 /**
@@ -104,7 +108,9 @@ IPCUnixSocket::Payload IPCMessage::payload() const
 
 	/* \todo Make this work without copy */
 	memcpy(payload.data.data() + sizeof(Header), data_.data(), data_.size());
-	payload.fds = fds_;
+
+	for (const FileDescriptor &fd : fds_)
+		payload.fds.push_back(fd.fd());
 
 	return payload;
 }
diff --git a/test/serialization/ipa_data_serializer_test.cpp b/test/serialization/ipa_data_serializer_test.cpp
index bf7e34e2..eca19a66 100644
--- a/test/serialization/ipa_data_serializer_test.cpp
+++ b/test/serialization/ipa_data_serializer_test.cpp
@@ -53,7 +53,7 @@ template<typename T>
 int testPodSerdes(T in)
 {
 	std::vector<uint8_t> buf;
-	std::vector<int32_t> fds;
+	std::vector<FileDescriptor> fds;
 
 	std::tie(buf, fds) = IPADataSerializer<T>::serialize(in);
 	T out = IPADataSerializer<T>::deserialize(buf, fds);
@@ -72,7 +72,7 @@ int testVectorSerdes(const std::vector<T> &in,
 		     ControlSerializer *cs = nullptr)
 {
 	std::vector<uint8_t> buf;
-	std::vector<int32_t> fds;
+	std::vector<FileDescriptor> fds;
 
 	std::tie(buf, fds) = IPADataSerializer<std::vector<T>>::serialize(in, cs);
 	std::vector<T> out = IPADataSerializer<std::vector<T>>::deserialize(buf, fds, cs);
@@ -92,7 +92,7 @@ int testMapSerdes(const std::map<K, V> &in,
 		  ControlSerializer *cs = nullptr)
 {
 	std::vector<uint8_t> buf;
-	std::vector<int32_t> fds;
+	std::vector<FileDescriptor> fds;
 
 	std::tie(buf, fds) = IPADataSerializer<std::map<K, V>>::serialize(in, cs);
 	std::map<K, V> out = IPADataSerializer<std::map<K, V>>::deserialize(buf, fds, cs);
@@ -219,7 +219,7 @@ private:
 		};
 
 		std::vector<uint8_t> buf;
-		std::vector<int32_t> fds;
+		std::vector<FileDescriptor> fds;
 
 		if (testVectorSerdes(vecUint8) != TestPass)
 			return TestFail;
@@ -291,7 +291,7 @@ private:
 			{ { "a", { 1, 2, 3 } }, { "b", { 4, 5, 6 } }, { "c", { 7, 8, 9 } } };
 
 		std::vector<uint8_t> buf;
-		std::vector<int32_t> fds;
+		std::vector<FileDescriptor> fds;
 
 		if (testMapSerdes(mapUintStr) != TestPass)
 			return TestFail;
@@ -359,7 +359,7 @@ private:
 		std::string strEmpty = "";
 
 		std::vector<uint8_t> buf;
-		std::vector<int32_t> fds;
+		std::vector<FileDescriptor> fds;
 
 		if (testPodSerdes(u32min) != TestPass)
 			return TestFail;
diff --git a/utils/ipc/generators/libcamera_templates/module_ipa_proxy.cpp.tmpl b/utils/ipc/generators/libcamera_templates/module_ipa_proxy.cpp.tmpl
index a4e008c7..aab1fffb 100644
--- a/utils/ipc/generators/libcamera_templates/module_ipa_proxy.cpp.tmpl
+++ b/utils/ipc/generators/libcamera_templates/module_ipa_proxy.cpp.tmpl
@@ -236,7 +236,7 @@ void {{proxy_name}}::recvMessage(const IPCMessage &data)
 void {{proxy_name}}::{{method.mojom_name}}IPC(
 	std::vector<uint8_t>::const_iterator data,
 	size_t dataSize,
-	[[maybe_unused]] const std::vector<int32_t> &fds)
+	[[maybe_unused]] const std::vector<FileDescriptor> &fds)
 {
 {%- for param in method.parameters %}
 	{{param|name}} {{param.mojom_name}};
diff --git a/utils/ipc/generators/libcamera_templates/module_ipa_proxy.h.tmpl b/utils/ipc/generators/libcamera_templates/module_ipa_proxy.h.tmpl
index c222f5f2..1979e68f 100644
--- a/utils/ipc/generators/libcamera_templates/module_ipa_proxy.h.tmpl
+++ b/utils/ipc/generators/libcamera_templates/module_ipa_proxy.h.tmpl
@@ -65,7 +65,7 @@ private:
 	void {{method.mojom_name}}IPC(
 		std::vector<uint8_t>::const_iterator data,
 		size_t dataSize,
-		const std::vector<int32_t> &fds);
+		const std::vector<FileDescriptor> &fds);
 {% endfor %}
 
 	/* Helper class to invoke async functions in another thread. */
diff --git a/utils/ipc/generators/libcamera_templates/proxy_functions.tmpl b/utils/ipc/generators/libcamera_templates/proxy_functions.tmpl
index ea9cc86b..ebcd2aaa 100644
--- a/utils/ipc/generators/libcamera_templates/proxy_functions.tmpl
+++ b/utils/ipc/generators/libcamera_templates/proxy_functions.tmpl
@@ -54,7 +54,7 @@
 {%- for param in params %}
 	std::vector<uint8_t> {{param.mojom_name}}Buf;
 {%- if param|has_fd %}
-	std::vector<int32_t> {{param.mojom_name}}Fds;
+	std::vector<FileDescriptor> {{param.mojom_name}}Fds;
 	std::tie({{param.mojom_name}}Buf, {{param.mojom_name}}Fds) =
 {%- else %}
 	std::tie({{param.mojom_name}}Buf, std::ignore) =
diff --git a/utils/ipc/generators/libcamera_templates/serializer.tmpl b/utils/ipc/generators/libcamera_templates/serializer.tmpl
index d8d55807..b8ef8e7b 100644
--- a/utils/ipc/generators/libcamera_templates/serializer.tmpl
+++ b/utils/ipc/generators/libcamera_templates/serializer.tmpl
@@ -40,7 +40,7 @@
 		retData.insert(retData.end(), {{field.mojom_name}}.begin(), {{field.mojom_name}}.end());
 {%- elif field|is_fd %}
 		std::vector<uint8_t> {{field.mojom_name}};
-		std::vector<int32_t> {{field.mojom_name}}Fds;
+		std::vector<FileDescriptor> {{field.mojom_name}}Fds;
 		std::tie({{field.mojom_name}}, {{field.mojom_name}}Fds) =
 			IPADataSerializer<{{field|name}}>::serialize(data.{{field.mojom_name}});
 		retData.insert(retData.end(), {{field.mojom_name}}.begin(), {{field.mojom_name}}.end());
@@ -58,7 +58,7 @@
 {%- elif field|is_plain_struct or field|is_array or field|is_map or field|is_str %}
 		std::vector<uint8_t> {{field.mojom_name}};
 	{%- if field|has_fd %}
-		std::vector<int32_t> {{field.mojom_name}}Fds;
+		std::vector<FileDescriptor> {{field.mojom_name}}Fds;
 		std::tie({{field.mojom_name}}, {{field.mojom_name}}Fds) =
 	{%- else %}
 		std::tie({{field.mojom_name}}, std::ignore) =
@@ -104,9 +104,9 @@
 		dataSize -= {{field_size}};
 	{%- endif %}
 {% elif field|is_fd %}
-	{%- set field_size = 1 %}
+	{%- set field_size = 4 %}
 		{{- check_data_size(field_size, 'dataSize', field.mojom_name, 'data')}}
-		ret.{{field.mojom_name}} = IPADataSerializer<{{field|name}}>::deserialize(m, m + 1, n, n + 1, cs);
+		ret.{{field.mojom_name}} = IPADataSerializer<{{field|name}}>::deserialize(m, m + {{field_size}}, n, n + 1, cs);
 	{%- if not loop.last %}
 		m += {{field_size}};
 		dataSize -= {{field_size}};
@@ -177,7 +177,7 @@
  # \a struct.
  #}
 {%- macro serializer(struct, namespace) %}
-	static std::tuple<std::vector<uint8_t>, std::vector<int32_t>>
+	static std::tuple<std::vector<uint8_t>, std::vector<FileDescriptor>>
 	serialize(const {{struct|name_full}} &data,
 {%- if struct|needs_control_serializer %}
 		  ControlSerializer *cs)
@@ -187,7 +187,7 @@
 	{
 		std::vector<uint8_t> retData;
 {%- if struct|has_fd %}
-		std::vector<int32_t> retFds;
+		std::vector<FileDescriptor> retFds;
 {%- endif %}
 {%- for field in struct.fields %}
 {{serializer_field(field, namespace, loop)}}
@@ -210,7 +210,7 @@
 {%- macro deserializer_fd(struct, namespace) %}
 	static {{struct|name_full}}
 	deserialize(std::vector<uint8_t> &data,
-		    std::vector<int32_t> &fds,
+		    std::vector<FileDescriptor> &fds,
 {%- if struct|needs_control_serializer %}
 		    ControlSerializer *cs)
 {%- else %}
@@ -224,8 +224,8 @@
 	static {{struct|name_full}}
 	deserialize(std::vector<uint8_t>::const_iterator dataBegin,
 		    std::vector<uint8_t>::const_iterator dataEnd,
-		    std::vector<int32_t>::const_iterator fdsBegin,
-		    std::vector<int32_t>::const_iterator fdsEnd,
+		    std::vector<FileDescriptor>::const_iterator fdsBegin,
+		    std::vector<FileDescriptor>::const_iterator fdsEnd,
 {%- if struct|needs_control_serializer %}
 		    ControlSerializer *cs)
 {%- else %}
@@ -234,7 +234,7 @@
 	{
 		{{struct|name_full}} ret;
 		std::vector<uint8_t>::const_iterator m = dataBegin;
-		std::vector<int32_t>::const_iterator n = fdsBegin;
+		std::vector<FileDescriptor>::const_iterator n = fdsBegin;
 
 		size_t dataSize = std::distance(dataBegin, dataEnd);
 		[[maybe_unused]] size_t fdsSize = std::distance(fdsBegin, fdsEnd);
@@ -255,7 +255,7 @@
 {%- macro deserializer_fd_simple(struct, namespace) %}
 	static {{struct|name_full}}
 	deserialize(std::vector<uint8_t> &data,
-		    [[maybe_unused]] std::vector<int32_t> &fds,
+		    [[maybe_unused]] std::vector<FileDescriptor> &fds,
 		    ControlSerializer *cs = nullptr)
 	{
 		return IPADataSerializer<{{struct|name_full}}>::deserialize(data.cbegin(), data.cend(), cs);
@@ -264,8 +264,8 @@
 	static {{struct|name_full}}
 	deserialize(std::vector<uint8_t>::const_iterator dataBegin,
 		    std::vector<uint8_t>::const_iterator dataEnd,
-		    [[maybe_unused]] std::vector<int32_t>::const_iterator fdsBegin,
-		    [[maybe_unused]] std::vector<int32_t>::const_iterator fdsEnd,
+		    [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsBegin,
+		    [[maybe_unused]] std::vector<FileDescriptor>::const_iterator fdsEnd,
 		    ControlSerializer *cs = nullptr)
 	{
 		return IPADataSerializer<{{struct|name_full}}>::deserialize(dataBegin, dataEnd, cs);