Re: [PATCH v2 12/13] vtpmmgr: Check req_len before unpacking command

["Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>]

On 5/6/21 9:59 AM, Jason Andryuk wrote:
> vtpm_handle_cmd doesn't ensure there is enough space before unpacking
> the req buffer.  Add a minimum size check.  Called functions will have
> to do their own checking if they need more data from the request.
> 
> The error case is tricky since abort_egress wants to rely with a
> corresponding tag.  Just hardcode TPM_TAG_RQU_COMMAND since the vtpm is
> sending in malformed commands in the first place.
> 
> Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx>
> ---

Reviewed-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>

>  stubdom/vtpmmgr/vtpm_cmd_handler.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/stubdom/vtpmmgr/vtpm_cmd_handler.c 
> b/stubdom/vtpmmgr/vtpm_cmd_handler.c
> index c879b24c13..5586be6997 100644
> --- a/stubdom/vtpmmgr/vtpm_cmd_handler.c
> +++ b/stubdom/vtpmmgr/vtpm_cmd_handler.c
> @@ -840,6 +840,12 @@ TPM_RESULT vtpmmgr_handle_cmd(
>       UINT32 size;
>       TPM_COMMAND_CODE ord;
>  
> +     if (tpmcmd->req_len < sizeof_TPM_RQU_HEADER(tpmcmd->req)) {
> +             status = TPM_BAD_PARAMETER;
> +             tag = TPM_TAG_RQU_COMMAND;
> +             goto abort_egress;
> +     }
> +
>       unpack_TPM_RQU_HEADER(tpmcmd->req,
>                       &tag, &size, &ord);
>  
>