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Fix write to uninitialized bytes for XCB event

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As the xcb_send_event man page [1] states,

  In order to properly initialize these bytes, we allocate 32 bytes
  even though we only need less for an xcb_configure_notify_event_t

This commit fixes the following Valgrind error, which could be
triggered by selecting a letter in LyX:

  ==12698== Syscall param writev(vector[...]) points to uninitialised byte(s)
  ==12698==    at 0x61F578D: __writev (writev.c:26)
  ==12698==    by 0x61F578D: writev (writev.c:24)
  ==12698==    by 0x4A83BFC: ??? (in /usr/lib/x86_64-linux-gnu/libxcb.so.1.1.0)
  ==12698==    by 0x4A83FD0: ??? (in /usr/lib/x86_64-linux-gnu/libxcb.so.1.1.0)
  ==12698==    by 0x4A84246: ??? (in /usr/lib/x86_64-linux-gnu/libxcb.so.1.1.0)
  ==12698==    by 0x4A84ACB: xcb_flush (in /usr/lib/x86_64-linux-gnu/libxcb.so.1.1.0)
  ==12698==    by 0x17C8F06: lyx::frontend::GuiApplication::nativeEventFilter(QByteArray const&, void*, long*) (GuiApplication.cpp:3366)
  ==12698==    by 0x5AA4EEE: QAbstractEventDispatcher::filterNativeEvent(QByteArray const&, void*, long*) (qabstracteventdispatcher.cpp:484)

[1] https://www.x.org/releases/current/doc/man/man3/xcb_send_event.3.xhtml
This commit is contained in:
Scott Kostyshak 2020-02-18 21:39:18 -05:00
parent b7af21ad7c
commit 19c41bd095
1 changed files with 16 additions and 8 deletions
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24
src/frontends/qt/GuiApplication.cpp
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@ -3352,18 +3352,26 @@ bool GuiApplication::nativeEventFilter(const QByteArray & eventType,
// not doing that, maybe because of our
// "persistent selection" implementation
// (see comments in GuiSelection.cpp).
xcb_selection_notify_event_t nev;
nev.response_type = XCB_SELECTION_NOTIFY;
nev.requestor = srev->requestor;
nev.selection = srev->selection;
nev.target = srev->target;
nev.property = XCB_NONE;
nev.time = XCB_CURRENT_TIME;
// It is expected that every X11 event is 32 bytes long,
// even if not all 32 bytes are needed. See:
// https://www.x.org/releases/current/doc/man/man3/xcb_send_event.3.xhtml
// TODO switch to Q_DECLARE_XCB_EVENT(event, xcb_selection_notify_event_t)
// once we require qt >= 5.6.3 or just copy the macro def.
xcb_selection_notify_event_t *nev = (xcb_selection_notify_event_t*) calloc(32, 1);
nev->response_type = XCB_SELECTION_NOTIFY;
nev->requestor = srev->requestor;
nev->selection = srev->selection;
nev->target = srev->target;
nev->property = XCB_NONE;
nev->time = XCB_CURRENT_TIME;
xcb_connection_t * con = QX11Info::connection();
xcb_send_event(con, 0, srev->requestor,
XCB_EVENT_MASK_NO_EVENT,
reinterpret_cast<char const *>(&nev));
reinterpret_cast<char const *>(nev));
xcb_flush(con);
free(nev);
#endif
return true;
}