KASAN: use-after-free Read in inet_shutdown

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger crash:

Reported-and-tested-by: <redacted>

Note: the tag will also help syzbot to understand when the bug is fixed.

Tested on https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master commit
617aebe6a97efa539cc4b8a52adccd89596e6be0 (Sun Feb 4 00:25:42 2018 +0000)
Merge tag 'usercopy-v4.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

compiler: gcc (GCC) 7.1.1 20170620
Patch is attached.
Kernel config is attached.


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