[PATCH 1/2] efi: Call FreePages only if needed

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

If the config file is builtin, cfg.addr will be zero but Xen
unconditionally calls FreePages() on the address.

Xen may also call FreePages() with a zero address if blexit() is called
after this point since cfg.need_to_free is not set to false.

The UEFI specification does not say whether calling FreePages() with a
zero address is allowed so let's be cautious and use cfg.need_to_free
properly.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---
 xen/common/efi/boot.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index 778a39cc48e6..50ff1d1bd225 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -1534,8 +1534,11 @@ void EFIAPI __init noreturn efi_start(EFI_HANDLE 
ImageHandle,
 
         efi_arch_cfg_file_late(loaded_image, dir_handle, section.s);
 
-        efi_bs->FreePages(cfg.addr, PFN_UP(cfg.size));
-        cfg.addr = 0;
+        if ( cfg.need_to_free )
+        {
+            efi_bs->FreePages(cfg.addr, PFN_UP(cfg.size));
+            cfg.need_to_free = false;
+        }
 
         if ( dir_handle )
             dir_handle->Close(dir_handle);
-- 
2.50.1