efi_loader: fix use after free in efi_exit() with tcg2

The efi_exit() function frees the loaded image memory by calling
efi_delete_image(). However, when CONFIG_EFI_TCG2_PROTOCOL is enabled, the
image_obj->image_type structure member is accessed after the memory has
been freed.

Fix this by performing the tcg2 measurement before the image deletion.

Fixes: 8fc4e0b4273a ("efi_loader: add boot variable measurement")
Suggested-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Tom Rini <trini@konsulko.com>
Cc: Masahisa Kojima <kojima.masahisa@socionext.com>
Acked-by: Masahisa Kojima <kojima.masahisa@socionext.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
index ddc935d22409803764e120deaaca431d752e6004..b424d924896743c31a4457e99ab73146fc2c799e 100644 (file)
--- a/lib/efi_loader/efi_boottime.c
+++ b/lib/efi_loader/efi_boottime.c
@@ -3494,12 +3494,6 @@ static efi_status_t EFIAPI efi_exit(efi_handle_t image_handle,
                if (ret != EFI_SUCCESS)
                        EFI_PRINT("%s: out of memory\n", __func__);
        }
-       /* efi_delete_image() frees image_obj. Copy before the call. */
-       exit_jmp = image_obj->exit_jmp;
-       *image_obj->exit_status = exit_status;
-       if (image_obj->image_type == IMAGE_SUBSYSTEM_EFI_APPLICATION ||
-           exit_status != EFI_SUCCESS)
-               efi_delete_image(image_obj, loaded_image_protocol);
 
        if (IS_ENABLED(CONFIG_EFI_TCG2_PROTOCOL)) {
                if (image_obj->image_type == IMAGE_SUBSYSTEM_EFI_APPLICATION) {
@@ -3510,6 +3504,13 @@ static efi_status_t EFIAPI efi_exit(efi_handle_t image_handle,
                }
        }
 
+       /* efi_delete_image() frees image_obj. Copy before the call. */
+       exit_jmp = image_obj->exit_jmp;
+       *image_obj->exit_status = exit_status;
+       if (image_obj->image_type == IMAGE_SUBSYSTEM_EFI_APPLICATION ||
+           exit_status != EFI_SUCCESS)
+               efi_delete_image(image_obj, loaded_image_protocol);
+
        /* Make sure entry/exit counts for EFI world cross-overs match */
        EFI_EXIT(exit_status);