On 20/09/2010 17:56, J. Bruce Fields wrote:
Ouch. Well, that's a problem.
(And have you checked the log files to make sure it's gssd segfaulting
and not some kind of crash in the kernel?)
--b.
Yes, it segfaults, even the log shows it. It's a null pointer exception.
I used gdb in gssd and this is my outcome:
0xb783f424 in __kernel_vsyscall ()
(gdb) c
Continuing.
Program received signal SIG37, Real-time event 37.
0xb783f424 in __kernel_vsyscall ()
(gdb) c
Continuing.
Program received signal SIG37, Real-time event 37.
0xb783f424 in __kernel_vsyscall ()
(gdb) c
Continuing.
Program received signal SIGSEGV, Segmentation fault.
0xb72b4c8e in __gss_get_mechanism_cred () from /usr/lib/libgssglue.so.1
(gdb) bt
#0 0xb72b4c8e in __gss_get_mechanism_cred () from /usr/lib/libgssglue.so.1
#1 0xb72b5c2c in gss_init_sec_context () from /usr/lib/libgssglue.so.1
#2 0xb776c215 in authgss_refresh () from /usr/lib/libtirpc.so.1
#3 0xb776c67d in authgss_create () from /usr/lib/libtirpc.so.1
#4 0xb776c779 in authgss_create_default () from /usr/lib/libtirpc.so.1
#5 0x0804cbdc in ?? ()
#6 0x0804cf9f in ?? ()
#7 0x0804d7c8 in ?? ()
#8 0x0804b7a8 in ?? ()
#9 0x0804b309 in ?? ()
#10 0xb761cc76 in __libc_start_main () from /lib/libc.so.6
#11 0x0804a621 in ?? ()
(gdb) info r
eax 0x0 0
ecx 0x9 9
edx 0x0 0
ebx 0xb72b9710 -1221880048
esp 0xbfe0b844 0xbfe0b844
ebp 0xbfe0b858 0xbfe0b858
esi 0x9 9
edi 0x9370928 154601768
eip 0xb72b4c8e 0xb72b4c8e <__gss_get_mechanism_cred+62>
eflags 0x210246 [ PF ZF IF RF ID ]
cs 0x73 115
ss 0x7b 123
ds 0x7b 123
es 0x7b 123
fs 0x0 0
gs 0x33 51
(gdb) disass $eip
Dump of assembler code for function __gss_get_mechanism_cred:
0xb72b4c50 <+0>: push %ebp
0xb72b4c51 <+1>: mov %esp,%ebp
0xb72b4c53 <+3>: push %edi
0xb72b4c54 <+4>: push %esi
0xb72b4c55 <+5>: sub $0xc,%esp
0xb72b4c58 <+8>: mov 0x8(%ebp),%ecx
0xb72b4c5b <+11>: test %ecx,%ecx
0xb72b4c5d <+13>: jne 0xb72b4c68 <__gss_get_mechanism_cred+24>
0xb72b4c5f <+15>: add $0xc,%esp
0xb72b4c62 <+18>: xor %eax,%eax
0xb72b4c64 <+20>: pop %esi
0xb72b4c65 <+21>: pop %edi
0xb72b4c66 <+22>: pop %ebp
0xb72b4c67 <+23>: ret
0xb72b4c68 <+24>: mov 0x8(%ebp),%eax
0xb72b4c6b <+27>: mov (%eax),%eax
0xb72b4c6d <+29>: test %eax,%eax
0xb72b4c6f <+31>: mov %eax,-0x10(%ebp)
0xb72b4c72 <+34>: jle 0xb72b4c5f <__gss_get_mechanism_cred+15>
0xb72b4c74 <+36>: mov 0xc(%ebp),%ecx
0xb72b4c77 <+39>: mov 0x8(%ebp),%eax
0xb72b4c7a <+42>: mov (%ecx),%edx
0xb72b4c7c <+44>: mov 0x4(%eax),%eax
0xb72b4c7f <+47>: mov %edx,-0x14(%ebp)
0xb72b4c82 <+50>: mov %eax,-0xc(%ebp)
0xb72b4c85 <+53>: xor %eax,%eax
0xb72b4c87 <+55>: nop
0xb72b4c88 <+56>: mov -0xc(%ebp),%edx
0xb72b4c8b <+59>: mov -0x14(%ebp),%ecx
=> 0xb72b4c8e <+62>: cmp (%edx,%eax,8),%ecx
0xb72b4c91 <+65>: jne 0xb72b4cab <__gss_get_mechanism_cred+91>
0xb72b4c93 <+67>: mov 0xc(%ebp),%edx
0xb72b4c96 <+70>: mov -0xc(%ebp),%ecx
0xb72b4c99 <+73>: mov 0x4(%edx),%esi
0xb72b4c9c <+76>: mov -0x14(%ebp),%edx
---Type <return> to continue, or q <return> to quit---q
Quit
(gdb) info r
eax 0x0 0
ecx 0x9 9
edx 0x0 0
ebx 0xb72b9710 -1221880048
esp 0xbfe0b844 0xbfe0b844
ebp 0xbfe0b858 0xbfe0b858
esi 0x9 9
edi 0x9370928 154601768
eip 0xb72b4c8e 0xb72b4c8e <__gss_get_mechanism_cred+62>
eflags 0x210246 [ PF ZF IF RF ID ]
cs 0x73 115
ss 0x7b 123
ds 0x7b 123
es 0x7b 123
fs 0x0 0
gs 0x33 51
Where you can see the null reference.
This, on the other hand, reminded me a discussion I had in the
fbsd-stable list, where somebody advised me to use des-cbc-crc keytabs,
and then experiment with other encryption types. Even though I didn't
have such issues in fbsd, this might be the case on this problem. Maybe
linux tries to compare an inexistent mech-type (or enc-type, whatever)
with one of it's list, and hence it segfaults. So, to shed a little more
light into the issue:
- the kdc (not the nfs-server) runs fbsd8, heimdal-1.2.1.
- on the linuxbox when I "kinit -k linuxclient" everything works fine.
- on the linux client "ktutil -k /etc/krb5.keytab list" shows:
/etc/krb5.keytab:
Vno Type Principal
Aliases
1 des-cbc-md5 host/linuxclient@EXAMPLE
1 des-cbc-md4 host/linuxclient@EXAMPLE
1 des-cbc-crc host/linuxclient@EXAMPLE
1 aes256-cts-hmac-sha1-96 host/linuxclient@EXAMPLE
1 des3-cbc-sha1 host/linuxclient@EXAMPLE
1 arcfour-hmac-md5 host/linuxclient@EXAMPLE
So maybe what I have to do next is to create a keytab of des-cbc-crc
encryption-type only for the client (maybe also for the nfsserver as
well..) and see how it'll behave...but I will do it tomorrow.
Until then,
mamalos
--
George Mamalakis
IT Officer
Electrical and Computer Engineer (Aristotle Un. of Thessaloniki),
MSc (Imperial College of London)
Department of Electrical and Computer Engineering
Faculty of Engineering
Aristotle University of Thessaloniki
phone number : +30 (2310) 994379
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