[efi] Veto the VMware UefiPxeBcDxe driver

The EDK2 UefiPxeBcDxe driver includes some remarkably convoluted and
unsafe logic in its driver binding protocol Start() and Stop() methods
in order to support a pair of nominally independent driver binding
protocols (one for IPv4, one for IPv6) sharing a single dynamically
allocated data structure.  This PXEBC_PRIVATE_DATA structure is
installed as a dummy protocol on the NIC handle in order to allow both
IPv4 and IPv6 driver binding protocols to locate it as needed.

The error handling code path in the UefiPxeBcDxe driver's Start()
method may attempt to uninstall the dummy protocol but fail to do so.
This failure is ignored and the containing memory is subsequently
freed anyway.  On the next invocation of the driver binding protocol,
it will find and use the already freed block of memory.  At some point
another memory allocation will occur, the PXEBC_PRIVATE_DATA structure
will be corrupted, and some undefined behaviour will occur.

The UEFI firmware used in VMware ESX 8 includes some proprietary
changes which attempt to install copies of the EFI_LOAD_FILE_PROTOCOL
and EFI_PXE_BASE_CODE_PROTOCOL instances from the IPv4 child handle
onto the NIC handle (along with a VMware-specific protocol with GUID
5190120d-453b-4d48-958d-f0bab3bc2161 and a NULL instance pointer).
This will inevitably fail with iPXE, since the NIC handle already
includes an EFI_LOAD_FILE_PROTOCOL instance.

These VMware proprietary changes end up triggering the unsafe error
handling code path described above.  The typical symptom is that an
attempt to exit from iPXE back to the UEFI firmware will crash the VM
with a General Protection fault from within the UefiPxeBcDxe driver:
this happens when the UefiPxeBcDriver's Stop() method attempts to call
through a function pointer in the (freed) PXEBC_PRIVATE_DATA
structure, but the function pointer has been overwritten by UCS-2
character data from a separate memory allocation.

Work around this failure by adding the VMware UefiPxeBcDxe driver to
the driver veto list.

Signed-off-by: Michael Brown <[email protected]>

Author: mcb30

src/interface/efi/efi_veto.c

@@ -435,6 +435,37 @@ efi_veto_hp_xhci ( EFI_DRIVER_BINDING_PROTOCOL *binding __unused,
 	return 0;
 }
 
+/**
+ * Veto VMware UefiPxeBcDxe driver
+ *
+ * @v binding		Driver binding protocol
+ * @v loaded		Loaded image protocol
+ * @v wtf		Component name protocol, if present
+ * @v manufacturer	Manufacturer name, if present
+ * @v name		Driver name, if present
+ * @ret vetoed		Driver is to be vetoed
+ */
+static int
+efi_veto_vmware_uefipxebc ( EFI_DRIVER_BINDING_PROTOCOL *binding __unused,
+			    EFI_LOADED_IMAGE_PROTOCOL *loaded __unused,
+			    EFI_COMPONENT_NAME_PROTOCOL *wtf __unused,
+			    const char *manufacturer, const CHAR16 *name ) {
+	static const CHAR16 uefipxebc[] = L"UEFI PXE Base Code Driver";
+	static const char *vmware = "VMware, Inc.";
+
+	/* Check manufacturer and driver name */
+	if ( ! manufacturer )
+		return 0;
+	if ( ! name )
+		return 0;
+	if ( strcmp ( manufacturer, vmware ) != 0 )
+		return 0;
+	if ( memcmp ( name, uefipxebc, sizeof ( uefipxebc ) ) != 0 )
+		return 0;
+
+	return 1;
+}
+
 /** Driver vetoes */
 static struct efi_veto efi_vetoes[] = {
 	{
@@ -445,6 +476,10 @@ static struct efi_veto efi_vetoes[] = {
 		.name = "HP Xhci",
 		.veto = efi_veto_hp_xhci,
 	},
+	{
+		.name = "VMware UefiPxeBc",
+		.veto = efi_veto_vmware_uefipxebc,
+	},
 };
 
 /**