usb: typec: fix potential array underflow in ucsi_ccg_sync_control()

commit e56aac6 upstream.

The "command" variable can be controlled by the user via debugfs.  The
worry is that if con_index is zero then "&uc->ucsi->connector[con_index
- 1]" would be an array underflow.

Fixes: 170a672 ("usb: typec: ucsi: add support for separate DP altmode devices")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/c69ef0b3-61b0-4dde-98dd-97b97f81d912@stanley.mountain
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ The function ucsi_ccg_sync_write() is renamed to ucsi_ccg_sync_control()
  in commit 13f2ec3 ("usb: typec: ucsi:simplify command sending API").
  Apply this patch to ucsi_ccg_sync_write() in 6.1.y accordingly. ]
Signed-off-by: Bin Lan <bin.lan.cn@windriver.com>
Signed-off-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/ucsi/ucsi_ccg.c

@@ -585,6 +585,10 @@ static int ucsi_ccg_sync_write(struct ucsi *ucsi, unsigned int offset,
 		    uc->has_multiple_dp) {
 			con_index = (uc->last_cmd_sent >> 16) &
 				    UCSI_CMD_CONNECTOR_MASK;
+			if (con_index == 0) {
+				ret = -EINVAL;
+				goto unlock;
+			}
 			con = &uc->ucsi->connector[con_index - 1];
 			ucsi_ccg_update_set_new_cam_cmd(uc, con, (u64 *)val);
 		}
@@ -600,6 +604,7 @@ static int ucsi_ccg_sync_write(struct ucsi *ucsi, unsigned int offset,
 err_clear_bit:
 	clear_bit(DEV_CMD_PENDING, &uc->flags);
 	pm_runtime_put_sync(uc->dev);
+unlock:
 	mutex_unlock(&uc->lock);
 
 	return ret;