Description of problem:
When attempting to depmod a kernel module using an "override" in a configuration file in /etc/depmod.d, the original module is selected as a higher priority, making it impossible to ever load an external module.

Version-Release number of selected component (if applicable):
kmod-20-15.el7_4.6
https://access.redhat.com/errata/RHBA-2017:3326

How reproducible:
Every time

Steps to Reproduce:
1. Create kernel module to use with override directive
2. echo "override <kmod-name> 3.10.0-* <kmod-name>" > /etc/depmod.d.<kmod-name>.conf
3. depmod
4. check /usr/lib/`uname -r`/modules.dep for <kmod-name>

Installing a kmod package should also cover steps 1-3

Actual results:
modules.dep contains original kernel module

Expected results:
modules.dep contains new module

Additional info:
Looking at depmod.c, and the function depmod_module_is_higher_priority in particular, there seems to have been a bug introduced when moving from el7_4.4 to el7_4.6.

newlen (and oldlen) were -= to cfg->dirnamelen + 1 in el7_4.4. However, in el7_4.6 they were expanded into new variables relnewlen and reloldlen which were made equal to {new,old}len - cfg->dirnamelen + 1. I believe these variables should be set equal to {new,old}len - (cfg->dirnamelen + 1) if we were to maintain the original arithmetic. Initial testing seems to prove that adding the parentheses should resolve the issue.