[Gllug] Help with a kernel crash

[John Edwards]

Hi
Could someone with an understanding of the Linux kernel memory internals 
give me a hand with this problem, or point me in the right direction ?

I've got a mail server on RedHat 7.3 running qmail, courier and Apache.
And this morning at 2:02 it locked up, with syslog reporting:

------------------------------------------------------------------------
Aug 15 02:02:15 sapo kernel: ------------[ cut here ]------------
Aug 15 02:02:15 sapo kernel: kernel BUG at page_alloc.c:115!
Aug 15 02:02:15 sapo kernel: invalid operand: 0000
Aug 15 02:02:15 sapo kernel: st scsi_mod ipchains natsemi ext3 jbd  
Aug 15 02:02:15 sapo kernel: CPU:    0
Aug 15 02:02:15 sapo kernel: EIP:    0010:[<c0131ab0>]    Not tainted
Aug 15 02:02:15 sapo kernel: EFLAGS: 00010286
Aug 15 02:02:15 sapo kernel: 
Aug 15 02:02:15 sapo kernel: EIP is at __free_pages_ok [kernel] 0x40 (2.4.18-5)
------------------------------------------------------------------------

I've had a look at "page_alloc.c" in the source code for RedHat's kernel 
version 2.4.18-5 (which the box is running) and lines 114 and 115 are:
	if (page->buffers)
		BUG();

So what is page->buffers and what could cause it to crash ?


The machine is a Pentium 166 with 256MB of RAM and had been running fine 
for over a year. A week ago a new hard drive was fitted and the OS was 
upgraded from RedHat 7.2 to RedHat 7.3.

The qmail logs show that mail was being processed at the time of the 
kernel crash. One mail at 02:01:02 was accepted and delivered and the 
next at 02:02:14 was accepted but not delivered locally. Mail is setup 
to be delivered by qmail into users' Maildirs.

Another thing that could be relavent is RAM is 256MB and swap space is 
260MB. Current memory load is:
------------------------------------------------------------------------
             total       used       free     shared    buffers     cached
Mem:        256212     252728       3484          0      56616     167244
-/+ buffers/cache:      28868     227344
Swap:       262040        124     261916
Total:      518252     252852     265400
------------------------------------------------------------------------



-- 
#------------------------------------------------------------#
|      John Edwards    Email: John.Edwards at uk.com            |
|                                                            |
|     "Security vulnerabilities are here to stay."           |
|   Scott Culp, Manager, Microsoft Security Response Center  |
#------------------------------------------------------------#

-- 
Gllug mailing list  -  Gllug at linux.co.uk
http://list.ftech.net/mailman/listinfo/gllug