incorrect permissions on /etc after installing mariadb rpms

Copied from https://answers.launchpad.net/maria/+question/214236

I am using centos.
when i am using yum or rpm to install mariadb-5.5.28, i find the permission of /usr and /etc folder has been changed.

before the installation
drwxr-xr-x 71 root root 4096 Nov 15 05:51 etc
drwxr-xr-x 71 root root 4096 Oct 8 17:06 usr

after the installation
drwxrwxr-x 71 root root 4096 Nov 15 06:21 etc
drwxrwxr-x 13 root root 4096 Nov 14 16:07 usr

I rebuilt it with source code follow this instructions and nothing changed...
https://kb.askmonty.org/en/building-mariadb-on-centos/

And indeed, rpm2cpio xxx|cpio -i --list -v shows that some directories in the rpms have rwxrwxr-x permissions, while others have rwxr-xr-x permissions.