tdf#97700 - vcl: opengl - add asserts for horrible size mismatch.

We really need to be sure that our texture and its wrapper agree on
the size of the texture, and particularly the buffer it is reading
into to avoid DMA'ing junk over the heap.

Add paranoid assertions, also add a canary at the end of the texture
so we fail hard and fast in this case.

Change-Id: Ibf4869fb5cba562aa117943ce0f2f3df21ca7036
Reviewed-on: https://gerrit.libreoffice.org/22252
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>

1 files changed, 28 insertions, 1 deletions

diff --git a/vcl/opengl/salbmp.cxx b/vcl/opengl/salbmp.cxx
index 0896fd1a8070..61d7575b7448 100644
--- a/vcl/opengl/salbmp.cxx
+++ b/vcl/opengl/salbmp.cxx
@@ -36,6 +36,10 @@
 
 #include "opengl/FixedTextureAtlas.hxx"
 
+#if OSL_DEBUG_LEVEL > 0
+#  define CANARY "tex-canary"
+#endif
+
 namespace
 {
 
@@ -145,6 +149,9 @@ bool OpenGLSalBitmap::Create( const OpenGLTexture& rTex, long nX, long nY, long
     mbDirtyTexture = false;
     VCL_GL_INFO( "Created texture " << maTexture.Id() );
 
+    assert(mnWidth == maTexture.GetWidth() &&
+           mnHeight == maTexture.GetHeight());
+
     return true;
 }
 
@@ -256,7 +263,15 @@ bool OpenGLSalBitmap::AllocateUserData()
     {
         try
         {
-            maUserBuffer.reset( new sal_uInt8[static_cast<sal_uInt32>(mnBytesPerRow) * mnHeight] );
+            size_t nToAllocate = static_cast<sal_uInt32>(mnBytesPerRow) * mnHeight;
+#if OSL_DEBUG_LEVEL > 0
+            nToAllocate += sizeof(CANARY);
+#endif
+            maUserBuffer.reset( new sal_uInt8[nToAllocate] );
+#if OSL_DEBUG_LEVEL > 0
+            memcpy(maUserBuffer.get() + nToAllocate - sizeof(CANARY),
+                   CANARY, sizeof(CANARY));
+#endif
             alloc = true;
         }
         catch (const std::bad_alloc &) {}
@@ -532,7 +547,19 @@ bool OpenGLSalBitmap::ReadTexture()
     {
         determineTextureFormat(mnBits, nFormat, nType);
 
+        // if this fails we can read too much into pData
+        assert(mnWidth == maTexture.GetWidth() &&
+               mnHeight == maTexture.GetHeight());
+
         maTexture.Read(nFormat, nType, pData);
+
+#if OSL_DEBUG_LEVEL > 0
+        // If we read over the end of pData we have a real hidden memory
+        // corruption problem !
+        size_t nCanary = static_cast<sal_uInt32>(mnBytesPerRow) * mnHeight;
+        assert(!memcmp(pData + nCanary, CANARY, sizeof (CANARY)));
+#endif
+
         mnBufWidth = mnWidth;
         mnBufHeight = mnHeight;
         return true;