EVR: fix potential crash on accessing to NV_DX_Interop extension

Under some circumstances wglGetExtensionsStringARB() may return null
pointer (unfortunately, it's still not clear why exactly this might
happen). As a result we get a crash in a subsequent strstr() call.
So for now we just add a simple null pointer check here to avoid the
crash.

Fixes: QTBUG-109710
Change-Id: Ia77ff7b4490f4b817ddddabfdc14750bd69118d0
Reviewed-by: Jøger Hansegård <joger.hansegard@qt.io>
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>
(cherry picked from commit 58e0ca625808cb91424d1be05ce3725fb746818f)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/src/plugins/multimedia/windows/evr/evrd3dpresentengine.cpp b/src/plugins/multimedia/windows/evr/evrd3dpresentengine.cpp
index 0548718a8..a6b167882 100644
--- a/src/plugins/multimedia/windows/evr/evrd3dpresentengine.cpp
+++ b/src/plugins/multimedia/windows/evr/evrd3dpresentengine.cpp
@@ -412,7 +412,12 @@ static bool readWglNvDxInteropProc(WglNvDxInterop &f)
 
     HWND hwnd = ::GetShellWindow();
     auto dc = ::GetDC(hwnd);
-    bool hasExtension = strstr(wglGetExtensionsStringARB(dc), "WGL_NV_DX_interop");
+
+    const char *wglExtString = wglGetExtensionsStringARB(dc);
+    if (!wglExtString)
+        qCDebug(qLcEvrD3DPresentEngine) << "WGL extensions missing (wglGetExtensionsStringARB returned null)";
+
+    bool hasExtension = wglExtString && strstr(wglExtString, "WGL_NV_DX_interop");
     ReleaseDC(hwnd, dc);
     if (!hasExtension) {
         qCDebug(qLcEvrD3DPresentEngine) << "WGL_NV_DX_interop missing";