request_module can sleep, thus we cannot hold rcu_read_lock() while
calling it. The function also jumps back and takes rcu_read_lock()
again (in xfrm_state_get_afinfo()), resulting in an imbalance.
This codepath is triggered whenever a new offloaded state is created.
Fixes: ffdb5211da ("xfrm: Auto-load xfrm offload modules")
Reported-by: syzbot+ca425f44816d749e8eb49755567a75ee48cf4a30@syzkaller.appspotmail.com
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>