Red Hat Bugzilla – Bug 141545
klogd will translate odd number of % (percent sign) into even number of percent signs
Last modified: 2007-11-30 17:07:15 EST
From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7) Gecko/20040804 Firefox/0.9.3 Description of problem: klogd retrieves kernel printk messages and sends them to syslogd after a little massaging. One of the massaging steps will turn an odd number of percent signs into an even number of percents signs using a non-reversible mechanism. For example, if the kernel performs printk(KERN_INFO "%s\n", "%");, the dmesg output buffer will properly show only a single % sign, while the syslog log files will have %%. Unfortunately, printking %% will also put %% into the syslog files. Thus, the transormation in klogd is non-reversible -- it is no longer clear how many percent signs there were in the kernel's output. I recommend that klogd be modified to no longer massage the kernel messages in non-reversible mechanisms. I expect a single % should work fine so long as klogd doesn't do something fantastically stupid like pass the kernel output to syslog() as the message format string. Version-Release number of selected component (if applicable): sysklogd-1.4.1-22 How reproducible: Always Steps to Reproduce: 1. Download and untar http://www.kernelnewbies.org/faq/sillymod.tar.gz (very small "hello world" kernel module) 2. Apply the patch I will attach shortly (very simple, amends the printk to include a single %) 3. run the ./configure and make steps 4. insmod ./sillymod.ko 5. Check dmesg output versus /var/log/messages output Actual Results: dmesg will report: Sillymod % loaded into 2.6.8-1.528.2.10. tail /var/log/messages: Dec 1 13:53:32 dhcp-246 kernel: Sillymod %% loaded into 2.6.8-1.528.2.10.
Created attachment 107743 [details] patch to sillymod that will change the printk to include a single percent sign Sillymod is pretty simple to work with: download, unpack, cd sillymod ; patch -p1 < /path/to/percent-problem.diff ; ./configure ; make ; sudo insmod ./sillymod.ko ; dmesg | tail ; sudo tail /var/log/messages There's nothing magic about sillymod; it was just a convenient example of a hello world kernel module.
This is now fixed - it was a hangover from the days when syslogd WAS "fantastically stupid" and was passing the message string as a *printf function fmt string. The new syslogd-1.4.1-24_EL that fixes this issue for RHEL-4 will be in RHEL-4-RC1 and meanwhile can be downloaded from: http://people.redhat.com/~jvdias/sysklogd .
Seth, does this new sysklogd fix things up for you?
Jason, Jay, yes, this fixes the problem! Many thanks. (I'm sorry I let this slip through the cracks -- I thought I couldn't find the packages at Jason's URL earlier on, so I assumed it had been taken down when the packages had been made available in the rhel 4 repos.. Much more likely is that I typo'd the URL when browsing from another machine. D'oh.)
Closing out.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on the solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHBA-2005-087.html