Request to cherry-pick c89dffc70b34 to 4.14, 4.19, and 5.4.

Hi maintainers,

Upstream commit 01770a166165 ("tcp: fix race condition when creating child sockets from syncookies") is planned to be backported to 4.14, 4.19 and 5.4:

https://marc.info/?l=linux-stable-commits&m=165063781908608&w=3 https://marc.info/?l=linux-stable-commits&m=165063781708604&w=3 https://marc.info/?l=linux-stable-commits&m=165063781708603&w=3

Another commit c89dffc70b34 ("tcp: Fix potential use-after-free due to double kfree()") has a Fixes tag for it, so please backport this also.

Best regards, Kuniyuki