diff --git a/Source/WebKit/ChangeLog b/Source/WebKit/ChangeLog
index 045d30e..260ef4a 100644
--- a/Source/WebKit/ChangeLog
+++ b/Source/WebKit/ChangeLog
@@ -1,3 +1,16 @@
+2020-03-26  Michael Catanzaro  <mcatanzaro@gnome.org>
+
+        Syscall param sendmsg(msg.msg_iov[0]) points to uninitialised byte(s) in IPC::Connection::sendOutgoingMessage
+        https://bugs.webkit.org/show_bug.cgi?id=146729
+
+        Reviewed by Carlos Garcia Campos.
+
+        The entire MessageInfo is passed to write(), so we have to zero the padding bytes to avoid
+        writing uninitialized memory.
+
+        * Platform/IPC/unix/UnixMessage.h:
+        (IPC::MessageInfo::MessageInfo):
+
 2020-03-25  Timothy Horton  <timothy_horton@apple.com>
 
         Unable to build WebKit with iOS 13.4 SDK
diff --git a/Source/WebKit/Platform/IPC/unix/UnixMessage.h b/Source/WebKit/Platform/IPC/unix/UnixMessage.h
index 6e98a73..243ce99 100644
--- a/Source/WebKit/Platform/IPC/unix/UnixMessage.h
+++ b/Source/WebKit/Platform/IPC/unix/UnixMessage.h
@@ -34,12 +34,18 @@
 
 class MessageInfo {
 public:
-    MessageInfo() = default;
+    MessageInfo()
+    {
+        // The entire MessageInfo is passed to write(), so we have to zero our
+        // padding bytes to avoid writing uninitialized memory.
+        memset(this, 0, sizeof(*this));
+    }
 
     MessageInfo(size_t bodySize, size_t initialAttachmentCount)
-        : m_bodySize(bodySize)
-        , m_attachmentCount(initialAttachmentCount)
     {
+        memset(this, 0, sizeof(*this));
+        m_bodySize = bodySize;
+        m_attachmentCount = initialAttachmentCount;
     }
 
     void setBodyOutOfLine()