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Bug 881729 - logsys: Race between logsys_format_set and log_printf_to_logs functions
logsys: Race between logsys_format_set and log_printf_to_logs functions
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: corosync (Show other bugs)
Unspecified Unspecified
low Severity low
: rc
: ---
Assigned To: Jan Friesse
Cluster QE
Depends On:
  Show dependency treegraph
Reported: 2012-11-29 08:13 EST by Jan Friesse
Modified: 2013-11-20 23:32 EST (History)
3 users (show)

See Also:
Fixed In Version: corosync-1.4.1-16.el6
Doc Type: Bug Fix
Doc Text:
Cause: Corosync logging system is reconfigured Consequence: Corosync can crash (with extremely low probability) with NULL pointer access Fix: Add proper locking of formatting variable Result: Corosync don't crash
Story Points: ---
Clone Of:
Last Closed: 2013-11-20 23:32:03 EST
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
Proposed patch (1.21 KB, patch)
2012-11-29 08:13 EST, Jan Friesse
no flags Details | Diff
Proposed patch - part 2 - Avoid deadlock (986 bytes, patch)
2012-12-03 03:42 EST, Jan Friesse
no flags Details | Diff

External Trackers
Tracker ID Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2013:1531 normal SHIPPED_LIVE corosync bug fix and enhancement update 2013-11-20 19:40:57 EST

  None (edit)
Description Jan Friesse 2012-11-29 08:13:42 EST
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):

How reproducible:

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) {
format_buffer = NULL;


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.
Comment 1 Jan Friesse 2012-12-03 03:42:08 EST
Created attachment 656433 [details]
Proposed patch - part 2 - Avoid deadlock
Comment 11 errata-xmlrpc 2013-11-20 23:32:03 EST
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.


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