ACK: [SRU][P-ESM/T/Z][CVE-2017-11176][PATCH] mqueue: fix a use-after-free in sys_mq_notify()

[Po-Hsu Lin]

As this is just a medium CVE, I think Precise-ESM does not need this.

The fix looks reasonable, and clean cherry-pick to T/Z, thus:
Acked-by: Po-Hsu Lin <po-hsu.lin at canonical.com>