Description: cgroup: fix cgroup_sk_alloc() for sk_clone_lock()
References:
 https://bugzilla.kernel.org/show_bug.cgi?id=208003
 https://lore.kernel.org/netdev/CAM_iQpUKQJrj8wE+Qa8NGR3P0L+5Uz=qo-O5+k_P60HzTde6aw%40mail.gmail.com/t/
 https://bugzilla.redhat.com/show_bug.cgi?id=1868453
 http://blog.pi3.com.pl/?p=720
Notes:
 carnil> Some care needs to be applied here to not make a released
 carnil> version affected by CVE-2020-25220. Additionally to the fixing
 carnil> commit refered there is need to apply "cgroup: add missing skcd-
 carnil> >no_refcnt check in cgroup_sk_alloc()" which was included in
 carnil> 4.9.233, 4.14.194 and 4.19.140.
Bugs:
 966846
upstream: released (5.8-rc5) [ad0f75e5f57ccbceec13274e1e242f2b5a6397ed]
4.19-upstream-stable: released (4.19.134) [0505cc4c908f46a4d22c4994dbbe7bc489d0c52d]
4.9-upstream-stable: released (4.9.231) [51fbad61b1dc2a082c7f7dbc3b1299a1e40c061a]
sid: released (5.7.10-1)
4.19-buster-security: released (4.19.146-1)
4.9-stretch-security: released (4.9.240-1)