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List:       linux-poweredge
Subject:    Re: LINUX kernel segment error 6
From:       Peter =?iso-8859-1?q?Kjellstr=F6m?= <cap () nsc ! liu ! se>
Date:       2011-08-24 12:25:32
Message-ID: 201108241425.36563.cap () nsc ! liu ! se
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On Tuesday, August 23, 2011 07:33:20 PM Stephen Dowdy wrote:
> mcclnx mcc wrote, On 08/23/2011 11:10 AM:
> > We have DELL R900 with REDHAT 5.5 installed.  Recently I found
> > /var/log/messages have following error come out.   I used DELL OPMN
> > check hardware but NO error. kernel: ctxhx[17268]: segfault at
> > 00007fff1fa6afd8 rip 00002b8022887c96 rsp 00007fff1fa6afe0 error 6
> 
> IANASE (I am not a Software Engineer, but...)
> 
> segcode() { s='';f=(PF_PROT PF_WRITE PF_USER PF_RSVD PF_INSTR); for i in
> $(seq 0 ${#f[*]}); do (( $1&(1<<$i) )) && { printf "%c%s" "$s"
> "${f[$i]}";s='|' ;}; done ; printf "\n" ;}
> 
> $ segcode 6
> PF_WRITE|PF_USER
> 
> The application 'ctxhx' attempted to write (PF_WRITE) in userland
> code (PF_USER) via the instruction at 00002b8022887c96 to a
> nonexistent page (address: 00007fff1fa6afd8) the stack pointer is
> 00007fff1fa6afe0 (note that you're trying to write slightly below
> the stack (8 bytes). that's probably not good, at least i think
> the stack grows upwards, but i'm not sure.  If it grows downward,
> then there's some stack protection in play and you have no more
> than 8bytes on the stack you can use..)

Very nice write-up :-) I'll only add that on x86(_64) the stack does grow 
downwards.

/Peter

> I.E. most likely bad code.
> 
> You might be able to pinpoint the code section from the binary  via:
> 
>     $ addr2line -e {path-of-binary}/ctxhx -f 00007fff1fa6afd8
> 
> to figure out where to fix the source code, assuming you have the
> source code.  Hmm, that seems unlikely, as a quick google search
> indicates this is an Oracle Document converter.  I guess if you
> have a support contract, report it to Oracle.
> 
> --stephen

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