Description: sctp: return error if the asoc has been peeled off in sctp_wait_for_sndbuf
References:
 https://sites.google.com/view/syzscope/warning-held-lock-freed
 https://syzkaller.appspot.com/bug?id=a8d38d1b68ffc744c53bd9b9fc1dbd6c86b1afe2
Notes:
Bugs:
upstream: released (4.15-rc9) [a0ff660058b88d12625a783ce9e5c1371c87951f]
5.10-upstream-stable: N/A "Fixed before branching point"
4.19-upstream-stable: N/A "Fixed before branching point"
4.9-upstream-stable: released (4.9.79) [2f056e7def4236bf5279da38410c93acee164d5a]
sid: released (4.14.17-1)
4.19-buster-security: N/A "Fixed before branching point"
4.9-stretch-security: released (4.9.80-1)