can: kvaser_usb_leaf: Fix overread with an invalid command

For command events read from the device,
kvaser_usb_leaf_read_bulk_callback() verifies that cmd->len does not
exceed the size of the received data, but the actual kvaser_cmd handlers
will happily read any kvaser_cmd fields without checking for cmd->len.

This can cause an overread if the last cmd in the buffer is shorter than
expected for the command type (with cmd->len showing the actual short
size).

Maximum overread seems to be 22 bytes (CMD_LEAF_LOG_MESSAGE), some of
which are delivered to userspace as-is.

Fix that by verifying the length of command before handling it.

This issue can only occur after RX URBs have been set up, i.e. the
interface has been opened at least once.

Cc: stable@vger.kernel.org
Fixes: 080f40a6 ("can: kvaser_usb: Add support for Kvaser CAN/USB devices")
Tested-by: Jimmy Assarsson <extja@kvaser.com>
Signed-off-by: Anssi Hannula <anssi.hannula@bitwise.fi>
Signed-off-by: Jimmy Assarsson <extja@kvaser.com>
Link: https://lore.kernel.org/all/20221010150829.199676-2-extja@kvaser.com


Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>