Segfault on large POST body

[mnutt]

I'm seeing a segfault when POSTing with a large-ish (400KB) content body when running a pillow server on qt 5.10. The segfault I get is:

#0  0x00007ffff4c1e77e in Pillow::HttpConnectionPrivate::initialize (this=0x60400000b080) at HttpConnection.cpp:146
#1  0x00007ffff4c1cac8 in Pillow::HttpConnection::initialize (this=0x600600007f60, inputDevice=0x6004002e5f10, outputDevice=0x6004002e5f10) at HttpConnection.cpp:664
#2  0x00007ffff4c10064 in Pillow::HttpServer::incomingConnection (this=0x7fffffffe330, socketDescriptor=12) at HttpServer.cpp:92
#3  0x00007ffff7f4a4b0 in QTcpServerPrivate::readNotification (this=0x60200000f940) at socket/qtcpserver.cpp:221
#4  0x00007ffff7f54441 in QReadNotifier::event (this=<optimized out>, e=<optimized out>) at socket/qnativesocketengine.cpp:1274
#5  0x00007ffff1735f3c in QApplicationPrivate::notify_helper (this=<optimized out>, receiver=0x6006000075a0, e=0x7fffffffde80) at kernel/qapplication.cpp:3732
#6  0x00007ffff173d070 in QApplication::notify (this=0x7fffffffe270, receiver=0x6006000075a0, e=0x7fffffffde80) at kernel/qapplication.cpp:3491
#7  0x00007ffff0d66d25 in QCoreApplication::notifyInternal2 (receiver=0x6006000075a0, event=event@entry=0x7fffffffde80) at kernel/qcoreapplication.cpp:1050
#8  0x00007ffff0dbaa0e in QCoreApplication::sendEvent (event=0x7fffffffde80, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:234
#9  socketNotifierSourceDispatch (source=0x601600009830) at kernel/qeventdispatcher_glib.cpp:106
#10 0x00007fffeb3afe14 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#11 0x00007fffeb3b0058 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#12 0x00007fffeb3b00fc in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#13 0x00007ffff0db9ddc in QEventDispatcherGlib::processEvents (this=0x60060000cfd0, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#14 0x00007fffe5483451 in QPAEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /opt/qt510/plugins/platforms/libheadless.so
#15 0x00007ffff0d652ab in QEventLoop::exec (this=this@entry=0x7fffffffe0a0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:212
#16 0x00007ffff0d6dc14 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1338
#17 0x0000000000453e1a in main (argc=1, argv=0x7fffffffe4b8) at main.cpp:130

The line: https://github.com/acossette/pillow/blob/master/pillowcore/HttpConnection.cpp#L146

When this happens, the first request actually completes successfully but the following request is the one that segfaults. I've debugged it, and it looks like _requestBuffer.data_ptr()->size is already zero so I'm not sure why setting it to zero again might be an issue?