In the Linux kernel, the following vulnerability has been resolved: mptcp: pm: ADD_ADDR rtx: free sk if last When an ADD_ADDR is retransmitted, the sk is held in sk_reset_timer(), and released at the end. If at that moment, it was the last reference being held, the sk would not be freed. sock_put() should then be called instead of __sock_put(). But that's not enough: if it is the last reference, sock_put() will call sk_free(), which will end up calling sk_stop_timer_sync() on the same timer, and waiting indefinitely to finish. So it is needed to mark that the timer is done at the end of the timer handler when it has not been rescheduled, not to call sk_stop_timer_sync() on "itself".
https://git.kernel.org/stable/c/b7b9a461569734d33d3259d58d2507adfac107ed
https://git.kernel.org/stable/c/b74ad20198652b6b39a761c277ba65ae82b1e107
https://git.kernel.org/stable/c/8143a224785ceaf2b0856e08d4498916f38228fb