OvmfPkg: QemuVideoDxe: tidy up error checking/handling in & under Start()

In QemuVideoControllerDriverStart():
- remove redundant zero-initialization of:
  - Private->Handle (2 locations)
  - Private->GopDevicePath (when at devpath end)

- remove fields used for error handling only:
  - PciAttributesSaved

- tigthen scope of temporaries:
  - MmioDesc
  - AcpiDeviceNode

- supplement missing error checks:
  - AppendDevicePathNode() can fail with out-of-memory (2 locations)
  - when installing GopDevicePath
  - retval of QemuVideoGraphicsOutputConstructor() (can justifiedly fail
    with out-of-resources)

- plug leaks on error:
  - free GopDevicePath (AppendDevicePathNode() allocates dynamically)
  - uninstall GopDevicePath
  - free Private->ModeData
  - call QemuVideoGraphicsOutputDestructor()
  - uninstall GOP

In QemuVideoGraphicsOutputConstructor(), called by Start():
- supplement missing error checks:
  - QemuVideoGraphicsOutputSetMode() retval (it can fail with
    out-of-resources)

- plug leaks on error:
  - free Mode->Info
  - free Mode

In QemuVideoCirrusModeSetup() and QemuVideoBochsModeSetup(), both called
by Start():
- supplement missing error checks:
  - AllocatePool() can fail in both

In QemuVideoGraphicsOutputDestructor(), called by Start() on the error
path:
- plug leaks:
  - free Private->LineBuffer, which is allocated in
    Start() -> Constructor() -> SetMode()

In QemuVideoGraphicsOutputSetMode(), called by Start() indirectly:
- remove redundant zero-assignment to:
  - Private->LineBuffer

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15282 6f19259b-4bc3-4df7-8a09-765794883524

OvmfPkg/QemuVideoDxe/Gop.c

@@ -176,7 +176,6 @@ Routine Description:
     gBS->FreePool (Private->LineBuffer);
   }
 
-  Private->LineBuffer = NULL;
   Private->LineBuffer = AllocatePool (4 * ModeData->HorizontalResolution);
   if (Private->LineBuffer == NULL) {
     return EFI_OUT_OF_RESOURCES;
@@ -321,13 +320,14 @@ QemuVideoGraphicsOutputConstructor (
   if (EFI_ERROR (Status)) {
     return Status;
   }
+
   Status = gBS->AllocatePool (
                   EfiBootServicesData,
                   sizeof (EFI_GRAPHICS_OUTPUT_MODE_INFORMATION),
                   (VOID **) &Private->GraphicsOutput.Mode->Info
                   );
   if (EFI_ERROR (Status)) {
-    return Status;
+    goto FreeMode;
   }
   Private->GraphicsOutput.Mode->MaxMode = (UINT32) Private->MaxMode;
   Private->GraphicsOutput.Mode->Mode    = GRAPHICS_OUTPUT_INVALIDE_MODE_NUMBER;
@@ -337,7 +337,11 @@ QemuVideoGraphicsOutputConstructor (
   //
   // Initialize the hardware
   //
-  GraphicsOutput->SetMode (GraphicsOutput, 0);
+  Status = GraphicsOutput->SetMode (GraphicsOutput, 0);
+  if (EFI_ERROR (Status)) {
+    goto FreeInfo;
+  }
+
   DrawLogo (
     Private,
     Private->ModeData[Private->GraphicsOutput.Mode->Mode].HorizontalResolution,
@@ -345,6 +349,15 @@ QemuVideoGraphicsOutputConstructor (
     );
 
   return EFI_SUCCESS;
+
+FreeInfo:
+  FreePool (Private->GraphicsOutput.Mode->Info);
+
+FreeMode:
+  FreePool (Private->GraphicsOutput.Mode);
+  Private->GraphicsOutput.Mode = NULL;
+
+  return Status;
 }
 
 EFI_STATUS
@@ -363,6 +376,10 @@ Returns:
 
 --*/
 {
+  if (Private->LineBuffer != NULL) {
+    FreePool (Private->LineBuffer);
+  }
+
   if (Private->GraphicsOutput.Mode != NULL) {
     if (Private->GraphicsOutput.Mode->Info != NULL) {
       gBS->FreePool (Private->GraphicsOutput.Mode->Info);