Re: INFO: rcu detected stall in wg_packet_tx_worker

[Jason A. Donenfeld]

On Sun, Apr 26, 2020 at 1:52 PM Jason A. Donenfeld <Jason@xxxxxxxxx> 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.