Description: l2tp: fix race in pppol2tp_release with session object destroy
References:
 https://source.android.com/docs/security/bulletin/pixel/2022-12-01
 https://android.googlesource.com/kernel/common/+/d02ba2a6110c5
Notes:
Bugs:
upstream: released (4.16-rc5) [d02ba2a6110c530a32926af8ad441111774d2893]
5.10-upstream-stable: N/A "Fixed before branching point"
4.19-upstream-stable: N/A "Fixed before branching point"
sid: released (4.15.11-1)
5.10-bullseye-security: N/A "Fixed before branching point"
4.19-buster-security: N/A "Fixed before branching point"