Re: INFO: rcu detected stall in wg_packet_tx_worker

On Sun, Apr 26, 2020 at 1:52 PM Jason A. Donenfeld Jason@zx2c4.com wrote:

It looks like part of the issue might be that I call udp_tunnel6_xmit_skb while holding rcu_read_lock_bh, in drivers/net/wireguard/socket.c. But I think there's good reason to do so, and udp_tunnel6_xmit_skb should be rcu safe. In fact, every.single.other user of udp_tunnel6_xmit_skb in the kernel uses it with rcu locked. So, hm...

In the syzkaller log, it looks like several runs are hitting:

run #0: crashed: INFO: rcu detected stall in netlink_sendmsg

And other runs are hitting yet different functions. So actually, it's not clear that this is the fault of the call to udp_tunnel6_xmit_skb.