[nginx-mainline] [Security] privilege escalation (CVE-2016-1247)

Summary
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The package nginx-mainline is vulnerable to privilege escalation via CVE-2016-1247.

Guidance
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The current permission setup on /var/log/nginx/ allows the privilege escalation to happen. We should adapt (like nearly all distros).

> ls -ld /var/log/nginx
drwxr-x--- 2 http log 4096 Jan 8 00:00 /var/log/nginx

To mitigate this issue, this should be:

> ls -ld /var/log/nginx
drwxr-xr-x 2 root root 20480 Jan 14 06:25 /var/log/nginx/

References
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