[U-Boot] [PATCH v2 2/2] efi_loader: parameter checks in StartImage and Exit()

[Takahiro Akashi <takahiro.akashi@linaro.org>]

On Fri, Apr 05, 2019 at 03:52:58AM +0200, Heinrich Schuchardt wrote:
> Add parameter checks in the StartImage() and Exit() boottime services:
> - check that the image handle is valid and has the loaded image protocol
>   installed
> - in StartImage() record the current image
> - in Exit() check that the image is the current image

Does this check logic work for a case of nested calls of StartImage() at all?

-Takahiro Akashi

> Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
> ---
> v2
> 	avoid `parent_image` may be used uninitialized
> ---
>  lib/efi_loader/efi_boottime.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
> index 6aac8391c5..970c01614e 100644
> --- a/lib/efi_loader/efi_boottime.c
> +++ b/lib/efi_loader/efi_boottime.c
> @@ -26,6 +26,9 @@ LIST_HEAD(efi_obj_list);
>  /* List of all events */
>  LIST_HEAD(efi_events);
> 
> +/* Handle of the currently executing image */
> +static efi_handle_t current_image;
> +
>  /*
>   * If we're running on nasty systems (32bit ARM booting into non-EFI Linux)
>   * we need to do trickery with caches. Since we don't want to break the EFI
> @@ -2631,9 +2634,18 @@ efi_status_t EFIAPI efi_start_image(efi_handle_t image_handle,
>  	struct efi_loaded_image_obj *image_obj =
>  		(struct efi_loaded_image_obj *)image_handle;
>  	efi_status_t ret;
> +	void *info;
> +	efi_handle_t parent_image = current_image;
> 
>  	EFI_ENTRY("%p, %p, %p", image_handle, exit_data_size, exit_data);
> 
> +	/* Check parameters */
> +	ret = EFI_CALL(efi_open_protocol(image_handle, &efi_guid_loaded_image,
> +					 &info, NULL, NULL,
> +					 EFI_OPEN_PROTOCOL_GET_PROTOCOL));
> +	if (ret != EFI_SUCCESS)
> +		return EFI_EXIT(EFI_INVALID_PARAMETER);
> +
>  	efi_is_direct_boot = false;
> 
>  	/* call the image! */
> @@ -2662,9 +2674,11 @@ efi_status_t EFIAPI efi_start_image(efi_handle_t image_handle,
>  		      __efi_nesting_dec(),
>  		      (unsigned long)((uintptr_t)image_obj->exit_status &
>  				      ~EFI_ERROR_MASK));
> +		current_image = parent_image;
>  		return EFI_EXIT(image_obj->exit_status);
>  	}
> 
> +	current_image = image_handle;
>  	ret = EFI_CALL(image_obj->entry(image_handle, &systab));
> 
>  	/*
> @@ -2699,12 +2713,23 @@ static efi_status_t EFIAPI efi_exit(efi_handle_t image_handle,
>  	 * TODO: We should call the unload procedure of the loaded
>  	 *	 image protocol.
>  	 */
> +	efi_status_t ret;
> +	void *info;
>  	struct efi_loaded_image_obj *image_obj =
>  		(struct efi_loaded_image_obj *)image_handle;
> 
>  	EFI_ENTRY("%p, %ld, %zu, %p", image_handle, exit_status,
>  		  exit_data_size, exit_data);
> 
> +	/* Check parameters */
> +	if (image_handle != current_image)
> +		goto out;
> +	ret = EFI_CALL(efi_open_protocol(image_handle, &efi_guid_loaded_image,
> +					 &info, NULL, NULL,
> +					 EFI_OPEN_PROTOCOL_GET_PROTOCOL));
> +	if (ret != EFI_SUCCESS)
> +		goto out;
> +
>  	/* Make sure entry/exit counts for EFI world cross-overs match */
>  	EFI_EXIT(exit_status);
> 
> @@ -2718,6 +2743,8 @@ static efi_status_t EFIAPI efi_exit(efi_handle_t image_handle,
>  	longjmp(&image_obj->exit_jmp, 1);
> 
>  	panic("EFI application exited");
> +out:
> +	return EFI_EXIT(EFI_INVALID_PARAMETER);
>  }
> 
>  /**
> --
> 2.20.1
>