Unable to handle kernel NULL pointer dereference

["Nicolas Ross" <rossnick-lists@cybercat.ca>]

Hi all !

I have a firewall box, with a vanilla kernel from kernel.org. I've tried
with 2.4.19 and 2.4.24. The system is RedHat 7.3 (it does the same thing
with 8.0, and gcc 3)

The kernel is pretty straigh-up, not much options, some net modules,
iptables etc.

The only thing out of the ordinary is a custom net/core/dev.c file to
support a bandwith management module, wich isn't gpl and is pre-compiled.

When issuing commands to configure the bandwith manager, I get :

Unable to handle kernel NULL pointer dereference at virtual address 00000000
 printing eip:
00000000
*pde = 00000000
Oops: 0000
CPU:    0
EIP:    0010:[<00000000>]    Tainted: P
EFLAGS: 00010086
eax: ddf5f948   ebx: ddf5e000   ecx: ddf5f980   edx: de9db400
esi: c0000000   edi: ddf5f986   ebp: ddf5f9b8   esp: ddf5f92c
ds: 0018   es: 0018   ss: 0018
Process bwmgr (pid: 1120, stackpage=ddf5f000)
Stack: e08c4431 de9db400 ddf5f980 00008946 fffffec4 11860f1f 00000000
0000000a
       00000000 00000001 00000000 00000000 00000000 00000000 00000000
00000000
       00000000 00bd0c00 00000000 00000000 90c8ebff 6e616c76 e08d0032
defec800
Call Trace:    [<e08c4431>] [<e08d0032>] [<e08d58d7>] [<e08d68b5>]
[<c012b346>]
  [<c0120ea3>] [<c012b346>] [<c012995a>] [<c0120ea3>] [<c0120f19>]
[<c010f303>]
  [<c028407e>] [<e08d95f6>] [<c01216de>] [<c010f1b0>] [<c01071b4>]
[<c0282bab>]
  [<c010f1b0>] [<c01071b4>] [<c0282bab>] [<e08af1f7>] [<e08c33ec>]
[<c01a3a17>]
  [<c023af54>] [<c023b138>] [<c023315a>] [<c013e413>] [<c01070a3>]

Code:  Bad EIP value.

After that the system still responds but isn't much usable, I have to
reboot, not practicall...

All of this was working with the exact same setup, but on a different MB,
and kernel 2.4.19.

Any hints on the source of this exception ?

Nicolas