Created attachment 654285 [details]
Proposed patch

Description of problem:
When logsys_format_set is called, it can set format to NULL and if
logsys thread is actually reading it, corosync can segfault (NULL
pointer access).

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

How reproducible:
0.00000000000001%

Steps to Reproduce:
1. Start corosync
2. Cause intensive logging of corosync (run cpgbench)
3. run corosync-objctl -w logging.fileline=on; corosync-objctl -w logging.fileline=off in cycle

or reliable with change in code:
- Add sleep in logsys_format_set function between lines

if (format_buffer) {
free(format_buffer);
format_buffer = NULL;

and

format_buffer = strdup(format ? format : "%p [%6s] %b");
if (format_buffer == NULL) {
ret = -1;

Actual results:
Corosync segfault

Expected results:
No segfault

Additional info:
For QA: Without change of code, I was unable to reproduce problem. Problem can be found by analysis of code. It was also reproduced by community (it's community patch). So it's worth to recommend bug as SanityOnly.