[PATCH] efi_loader: Trim output buffer size correctly for tee variables

[Heinrich Schuchardt]

On 22.07.20 00:50, Ilias Apalodimas wrote:
> The current code does not trim the output buffer correctly.
> In fact it doesn't trim the buffer at all, since it calculates a wrong
> value for it, which isn't even applied.
> So let's remove the unused temporary size variable and trim the buffer
> correctly.
> Since we are editing efi_get_next_variable_name_int(), fix an indentation
> error along the way.
>
> Fixes: f042e47e8fb43 ("efi_loader: Implement EFI variable handling via OP-TEE")
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> ---
>  lib/efi_loader/efi_variable_tee.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
>
> diff --git a/lib/efi_loader/efi_variable_tee.c b/lib/efi_loader/efi_variable_tee.c
> index c0423489388a..0e5b4479d936 100644
> --- a/lib/efi_loader/efi_variable_tee.c
> +++ b/lib/efi_loader/efi_variable_tee.c
> @@ -410,7 +410,6 @@ efi_status_t efi_get_next_variable_name_int(efi_uintn_t *variable_name_size,
>  	efi_uintn_t payload_size;
>  	efi_uintn_t out_name_size;
>  	efi_uintn_t in_name_size;
> -	efi_uintn_t tmp_dsize;
>  	u8 *comm_buf = NULL;
>  	efi_status_t ret;
>
> @@ -433,13 +432,8 @@ efi_status_t efi_get_next_variable_name_int(efi_uintn_t *variable_name_size,
>  	}
>
>  	/* Trim output buffer size */
> -	tmp_dsize = *variable_name_size;
> -	if (in_name_size + tmp_dsize >
> -			max_payload_size - MM_VARIABLE_GET_NEXT_HEADER_SIZE) {
> -		tmp_dsize = max_payload_size -
> -				MM_VARIABLE_GET_NEXT_HEADER_SIZE -
> -				in_name_size;
> -	}
> +	if (out_name_size > max_payload_size - MM_VARIABLE_GET_NEXT_HEADER_SIZE)
> +		out_name_size = max_payload_size - MM_VARIABLE_GET_NEXT_HEADER_SIZE;
>
>  	payload_size = MM_VARIABLE_GET_NEXT_HEADER_SIZE + out_name_size;
>  	comm_buf = setup_mm_hdr((void **)&var_getnext, payload_size,
> @@ -465,8 +459,7 @@ efi_status_t efi_get_next_variable_name_int(efi_uintn_t *variable_name_size,
>  		goto out;
>
>  	guidcpy(guid, &var_getnext->guid);
> -	memcpy(variable_name, (u8 *)var_getnext->name,
> -	       var_getnext->name_size);
> +	memcpy(variable_name, (u8 *)var_getnext->name, var_getnext->name_size);

var_getnext->name is already a pointer. There is no need to convert this
to (u8 *) as memcpy expects (void *) and will accept any pointer.

I will remove that conversion when merging.

Reviewed-by: Heinrich Schuchardt <xypron.glpk at gmx.de>

>
>  out:
>  	free(comm_buf);
>