kasan: GPF could be caused by NULL-ptr deref or user memory access
RIP: 0010:dst_dev_put+0x24/0x290 net/core/dst.c:168
<IRQ>
rt_fibinfo_free_cpus net/ipv4/fib_semantics.c:200 [inline]
free_fib_info_rcu+0x2e1/0x490 net/ipv4/fib_semantics.c:217
__rcu_reclaim kernel/rcu/rcu.h:240 [inline]
rcu_do_batch kernel/rcu/tree.c:2437 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline]
rcu_process_callbacks+0x100a/0x1ac0 kernel/rcu/tree.c:2697
...
They were caused by the fib_nh_common percpu member 'nhc_pcpu_rth_output'
overwritten by another percpu variable 'dev->tstats' access overflow in
tipc udp media xmit path when counting packets on a non tunnel device.
The fix is to make udp tunnel work with no tunnel device by allowing not
to count packets on the tstats when the tunnel dev is NULL in Patches 1/3
and 2/3, then pass a NULL tunnel dev in tipc_udp_tunnel() in Patch 3/3.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>