Slackware 9.1 kernel 2.4.22
Intalling a mobile phone for Intenet connection I find an Oops message when I disconnect it (ppp-off) in syslog:

Unable to handle kernel NULL pointer dereference at virtual address 00000014
printing eip:
e0cdf3f4
*pde = 00000000
Oops: 0000
CPU: 0
EIP: 0010:[<e0cdf3f4>] Tainted: PF
EFLAGS: 00010087
eax: dee4d400 ebx: db1328f0 ecx: 00000005 edx: 00000000
esi: defea170 edi: db1328f0 ebp: 00000286 esp: c2f5fe90
ds: 0018 es: 0018 ss: 0018
Process pppd (pid: 2329, stackpage=c2f5f000)
Stack: db1328f0 defea170 dee7624c 00000282 e0ce00cd db1328f0 db1328f4 db132df0
c723fc1c c8145000 00000000 e0cc639a db1328f0 e52a310f db1328f0 c723fc1c
c723fc1c e52aa551 c723fc1c c38ef970 c723fc74 e52aa5fb c723fc1c c38ef970
Call Trace: [<e0ce00cd>] [<e0cc639a>] [<e52a310f>] [<e52aa551>] [<e52aa5fb>]
[<c01eb588>] [<c014b907>] [<c014ceff>] [<c01eb9ea>] [<c0138c3a>] [<c0137587>]
[<c01375f3>] [<c0108f13>]

Code: 8b 52 14 83 ea 1c 8b 42 04 8b 5a 08 25 00 00 00 2f 0d 00 00

The connection works, but when I dosconnect it, generate the Oops (tail syslog) and generate a lock (var/lock/) file so is not possible to reconnect again with ppp-on it remain in the process and is not possible to kill it the only way to reconnect is thrue reboot the system and start again.