RE: [char-misc-next V2] mei: hdcp: fix mei_hdcp_verify_mprime() input paramter

["Winkler, Tomas" <tomas.winkler@intel.com>]

> > Hi Tomas,
> >
> > On 7/30/20 02:02, Tomas Winkler wrote:
> > > wired_cmd_repeater_auth_stream_req_in has a variable length array at
> > > the end. we use struct_size() overflow macro to determine the size
> > > for the allocation and sending size.
> > >
> >
> > My comments here:
> > https://lore.kernel.org/lkml/66c9950c-ef54-423e-467f-
> > 38a9f7afb384@embeddedor.com/
> Strange,  it haven't landed in my mailbox
> 
> 
> > still stand...
> 
> 
> 1. I don't think it should go to stable, true  there was bug but it wasn't
> triggered because there is only one stream.


I'm changing my mind on that, this is a pretty security issue, it should be fixed in stable. 

> 2. In any case if we want to backport to stable, than all those fancy overflow
> macros are not there yet, need to rewrite the patch.
> 2. We cannot flex_array_size() as the streams in hdcp_port_data is not an
> array, I'm not going to change it in this patch.

Last, forgot to thanks you for your persistent and thoroughly review. 
 
> >
> > > Fixes: c56967d674e3 (mei: hdcp: Replace one-element array with
> > > flexible-array member)
> > > Fixes: c56967d674e3 (mei: hdcp: Replace one-element array with
> > > flexible-array member)
> 
> > You have repeated the same commit twice, above.
> Will fix
>  Also, a Fixes tag for the
> 
> > commit from Feb 2019 that I talk about here:
> > https://lore.kernel.org/lkml/66c9950c-ef54-423e-467f-
> > 38a9f7afb384@embeddedor.com/
> Will add
> > should be included in this changelog text.
> >
> > --
> > Gustavo
> >
> > > Cc: Ramalingam C <ramalingam.c@intel.com>
> > > Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
> > > Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
> > > ---
> > > V2: Check for allocation failure.
> > >  drivers/misc/mei/hdcp/mei_hdcp.c | 40
> > > +++++++++++++++++++-------------
> > >  1 file changed, 24 insertions(+), 16 deletions(-)
> > >
> > > diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c
> > > b/drivers/misc/mei/hdcp/mei_hdcp.c
> > > index d1d3e025ca0e..f1205e0060db 100644
> > > --- a/drivers/misc/mei/hdcp/mei_hdcp.c
> > > +++ b/drivers/misc/mei/hdcp/mei_hdcp.c
> > > @@ -546,38 +546,46 @@ static int mei_hdcp_verify_mprime(struct
> > > device
> > *dev,
> > >  				  struct hdcp_port_data *data,
> > >  				  struct hdcp2_rep_stream_ready
> > *stream_ready)  {
> > > -	struct wired_cmd_repeater_auth_stream_req_in
> > > -					verify_mprime_in = { { 0 } };
> > > +	struct wired_cmd_repeater_auth_stream_req_in *verify_mprime_in;
> > >  	struct wired_cmd_repeater_auth_stream_req_out
> > >  					verify_mprime_out = { { 0 } };
> > >  	struct mei_cl_device *cldev;
> > >  	ssize_t byte;
> > > +	size_t cmd_size;
> > >
> > >  	if (!dev || !stream_ready || !data)
> > >  		return -EINVAL;
> > >
> > >  	cldev = to_mei_cl_device(dev);
> > >
> > > -	verify_mprime_in.header.api_version = HDCP_API_VERSION;
> > > -	verify_mprime_in.header.command_id =
> > WIRED_REPEATER_AUTH_STREAM_REQ;
> > > -	verify_mprime_in.header.status = ME_HDCP_STATUS_SUCCESS;
> > > -	verify_mprime_in.header.buffer_len =
> > > +	cmd_size = struct_size(verify_mprime_in, streams, data->k);
> > > +	if (cmd_size == SIZE_MAX)
> > > +		return -EINVAL;
> > > +
> > > +	verify_mprime_in = kzalloc(cmd_size, GFP_KERNEL);
> > > +	if (!verify_mprime_in)
> > > +		return -ENOMEM;
> > > +
> > > +	verify_mprime_in->header.api_version = HDCP_API_VERSION;
> > > +	verify_mprime_in->header.command_id =
> > WIRED_REPEATER_AUTH_STREAM_REQ;
> > > +	verify_mprime_in->header.status = ME_HDCP_STATUS_SUCCESS;
> > > +	verify_mprime_in->header.buffer_len =
> > >
> > 	WIRED_CMD_BUF_LEN_REPEATER_AUTH_STREAM_REQ_MIN_IN;
> > >
> > > -	verify_mprime_in.port.integrated_port_type = data->port_type;
> > > -	verify_mprime_in.port.physical_port = (u8)data->fw_ddi;
> > > -	verify_mprime_in.port.attached_transcoder = (u8)data->fw_tc;
> > > +	verify_mprime_in->port.integrated_port_type = data->port_type;
> > > +	verify_mprime_in->port.physical_port = (u8)data->fw_ddi;
> > > +	verify_mprime_in->port.attached_transcoder = (u8)data->fw_tc;
> > > +
> > > +	memcpy(verify_mprime_in->m_prime, stream_ready->m_prime,
> > HDCP_2_2_MPRIME_LEN);
> > > +	drm_hdcp_cpu_to_be24(verify_mprime_in->seq_num_m, data-
> > >seq_num_m);
> > >
> > > -	memcpy(verify_mprime_in.m_prime, stream_ready->m_prime,
> > > -	       HDCP_2_2_MPRIME_LEN);
> > > -	drm_hdcp_cpu_to_be24(verify_mprime_in.seq_num_m, data-
> > >seq_num_m);
> > > -	memcpy(verify_mprime_in.streams, data->streams,
> > > +	memcpy(verify_mprime_in->streams, data->streams,
> > >  	       array_size(data->k, sizeof(*data->streams)));
> > >
> > > -	verify_mprime_in.k = cpu_to_be16(data->k);
> > > +	verify_mprime_in->k = cpu_to_be16(data->k);
> > >
> > > -	byte = mei_cldev_send(cldev, (u8 *)&verify_mprime_in,
> > > -			      sizeof(verify_mprime_in));
> > > +	byte = mei_cldev_send(cldev, (u8 *)&verify_mprime_in, cmd_size);
> > > +	kfree(verify_mprime_in);
> > >  	if (byte < 0) {
> > >  		dev_dbg(dev, "mei_cldev_send failed. %zd\n", byte);
> > >  		return byte;
> > >