usb: typec: fix potential out of bounds in ucsi_ccg_update_set_new_cam_cmd()

The "*cmd" variable can be controlled by the user via debugfs.  That means
"new_cam" can be as high as 255 while the size of the uc->updated[] array
is UCSI_MAX_ALTMODES (30).

The call tree is:
ucsi_cmd() // val comes from simple_attr_write_xsigned()
-> ucsi_send_command()
   -> ucsi_send_command_common()
      -> ucsi_run_command() // calls ucsi->ops->sync_control()
         -> ucsi_ccg_sync_control()

Fixes: 170a6726d0e2 ("usb: typec: ucsi: add support for separate DP altmode devices")
Cc: stable <stable@kernel.org>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/325102b3-eaa8-4918-a947-22aca1146586@stanley.mountain
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/typec/ucsi/ucsi_ccg.c b/drivers/usb/typec/ucsi/ucsi_ccg.c
index ba58d11907bc589564bc6e91b518ba5700a59bfb..bccfc03b5986d720a6257584b7b99d68c0ecd421 100644 (file)
--- a/drivers/usb/typec/ucsi/ucsi_ccg.c
+++ b/drivers/usb/typec/ucsi/ucsi_ccg.c
@@ -482,6 +482,8 @@ static void ucsi_ccg_update_set_new_cam_cmd(struct ucsi_ccg *uc,
 
        port = uc->orig;
        new_cam = UCSI_SET_NEW_CAM_GET_AM(*cmd);
+       if (new_cam >= ARRAY_SIZE(uc->updated))
+               return;
        new_port = &uc->updated[new_cam];
        cam = new_port->linked_idx;
        enter_new_mode = UCSI_SET_NEW_CAM_ENTER(*cmd);