In the Linux kernel, the following vulnerability has been resolved:

mptcp: pm: ADD_ADDR rtx: fix potential data-race

This mptcp_pm_add_timer() helper is executed as a timer callback in
softirq context. To avoid any data races, the socket lock needs to be
held with bh_lock_sock().

If the socket is in use, retry again soon after, similar to what is done
with the keepalive timer.