On 7/29/20 12:32, 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.
>
> Fixes: c56967d674e3 (mei: hdcp: Replace one-element array with flexible-array
> member)
This also fixes:
commit 0a1af1b5c18d ("misc/mei/hdcp: Verify M_prime")
which introduced a potential stack overflow back in Feb 2019, hence it should be
fixed in -stable, too.
So, either both commit c56967d674e3 (mei: hdcp: Replace one-element array with
flexible-array member)
and this patch should be ported to -stable in order to fix a potential
stack overflow due to commit 0a1af1b5c18d ("misc/mei/hdcp: Verify M_prime"),
or a separate fix that doesn't touch the one-element array streams[1] in struct
wired_cmd_repeater_auth_stream_req_in, but addresses the stack overflow should
be crafted and applied to -stable.
I can write that fix up for -stable if you want to go in that direction. Just
let
me know.
> Cc: Ramalingam C <ramalinga...@intel.com>
> Cc: Gustavo A. R. Silva <gustavo...@kernel.org>
> Signed-off-by: Tomas Winkler <tomas.wink...@intel.com>
> ---
> drivers/misc/mei/hdcp/mei_hdcp.c | 38 ++++++++++++++++++--------------
> 1 file changed, 22 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c
> b/drivers/misc/mei/hdcp/mei_hdcp.c
> index d1d3e025ca0e..0e8f12e38494 100644
> --- a/drivers/misc/mei/hdcp/mei_hdcp.c
> +++ b/drivers/misc/mei/hdcp/mei_hdcp.c
> @@ -546,38 +546,44 @@ 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);
> +
> + 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)));
Please, use flex_array_size() instead of array_size() here, like this:
memcpy(verify_mprime_in->streams, data->streams,
flex_array_size(verify_mprime_in, streams, data->k));
Thanks
--
Gustavo
>
> - 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;
>
