mei: hdcp: fix mei_hdcp_verify_mprime() input parameter

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.
This also fixes bug in case number of streams is > 0 in the original
submission. This bug was not triggered as the number of streams is
always one.

Fixes: c56967d674e3 (mei: hdcp: Replace one-element array with flexible-array member)
Fixes: 0a1af1b5c18d (misc/mei/hdcp: Verify M_prime)
Cc: <stable@vger.kernel.org> # v5.1+: c56967d674e3 (mei: hdcp: Replace one-element array with flexible-array member)
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20200818075406.2532605-1-tomas.winkler@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c b/drivers/misc/mei/hdcp/mei_hdcp.c
index d1d3e025ca0e8799e44242831233e5dc23a9c3a1..9ae9669e46eae92d12906d86bcf2ef80c75488aa 100644 (file)
--- 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;