Bug 450219

Description of problem:

Some error conditions handled by the bonding sysfs interface on 5.2 can leave 
the rtnl_lock unbalanced, either by locking and returning without unlocking, 
or by unlocking when it didn't lock.

If one sees kernel messages about bonding and then RTNL asserts failing, it's 
very likely to be the issues pointed out here.

kernel: bonding: bond1: Unable to update slaves because interface is down.
...
kernel: RTNL: assertion failed at net/core/fib_rules.c (388)
... repeats many times and at several points in the code.

That "unable to update slaves" message is precisely the point where 
bonding_store_slaves() does an unbalanced unlock.

Version-Release number of selected component (if applicable):

First noticed on 2.6.18-92.el5, but the code changes happened over a few 
earlier commits starting at -62.el5 (bug 268001).

How reproducible:

Looking at the code I guess 100%. :)

Steps to Reproduce:

Hits a customer, I could not try on the lab yet. I figure adding a NIC to a 
bond that is down could trigger this easily.
  
Actual results:

RTNL lock cannot be trusted after those errors and I gather networking would 
get quite racy.

Expected results:

RTNL lock nicely managed.

Additional info:

Patch attached, already in a test package on a customer. Will post results as 
soon as the tests are done. Looking at the code for bonding_store_bonds() and 
bonding_store_slaves() it is easy to spot those problems.