Description: vsock: fix the race conditions in multi-transport support
References:
 https://a13xp0p0v.github.io/2021/02/09/CVE-2021-26708.html
Notes:
 carnil> Introduced in c0cfa2d8a788fcf4 and 6a2c0962105ae8ce in 5.5-rc1.
Bugs:
upstream: released (5.11-rc7) [c518adafa39f37858697ac9309c6cf1805581446]
5.10-upstream-stable: released (5.10.13) [55d900415b81680bcd5f93be51f26ebfc51ac6fb]
4.19-upstream-stable: N/A "Vulnerable code introduced later"
4.9-upstream-stable: N/A "Vulnerable code introduced later"
sid: released (5.10.13-1)
4.19-buster-security: N/A "Vulnerable code introduced later"
4.9-stretch-security: N/A "Vulnerable code introduced later"