BUG on dpt_i2o module removal

BUG on dpt_i2o module removal

[Meelis Roos]

While trying to "rmmod dpt_i2o" in 1.6.39 with one unused DPT SmartRAID 
V card in the system, I got the following BUG:

[  776.979914] BUG: unable to handle kernel NULL pointer dereference at 00000004
[  776.980018] IP: [<c11845ea>] scsi_unregister+0xf/0x34
[  776.980018] *pde = 00000000 
[  776.980018] Oops: 0002 [#1] PREEMPT 
[  776.980018] last sysfs file: /sys/devices/pci0000:00/0000:00:1e.0/class
[  776.980018] Modules linked in: snd_hrtimer ppdev lp uinput fuse nfsd nfs lockd auth_rpcgss nfs_acl sunrpc ipv6 adm1025 hwmon_vid smsc47m1 usb_storage usb_libusual udf crc_itu_t isofs zlib_inflate vfat fat eeprom ntfs i2o_core snd_intel8x0 snd_ac97_codec ac97_bus snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy snd_seq_oss snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq sg snd_timer sr_mod snd_seq_device radeon cdrom snd ttm evdev uhci_hcd soundcore drm_kms_helper hwmon cfbcopyarea ehci_hcd snd_page_alloc dpt_i2o(-) cfbimgblt usbcore cfbfillrect parport_pc i2c_i801 parport processor button
[  776.980018] 
[  776.980018] Pid: 2051, comm: rmmod Not tainted 2.6.39 #373                  /D815EEA2                       
[  776.980018] EIP: 0060:[<c11845ea>] EFLAGS: 00210292 CPU: 0
[  776.980018] EIP is at scsi_unregister+0xf/0x34
[  776.980018] EAX: dea27000 EBX: dea27000 ECX: 00000000 EDX: 00000000
[  776.980018] ESI: 00000000 EDI: 00000880 EBP: d8ca9f4c ESP: d8ca9f4c
[  776.980018]  DS: 007b ES: 007b FS: 0000 GS: 00e0 SS: 0068
[  776.980018] Process rmmod (pid: 2051, ti=d8ca8000 task=df791b40 task.ti=d8ca8000)
[  776.980018] Stack:
[  776.980018]  d8ca9f5c e083bc42 e083e164 00000000 d8ca9fac c1042d18 5f747064 006f3269
[  776.980018]  df70aa60 df79822c d8ca9f9c c106a12e ffffffff b785e000 b785d000 b785e000
[  776.980018]  df798e34 df70aa60 df70aa94 00000000 00ca9fac cff7145c bff033a0 bff033a0
[  776.980018] Call Trace:
[  776.980018]  [<e083bc42>] adpt_exit+0x39/0x3f7 [dpt_i2o]
[  776.980018]  [<c1042d18>] sys_delete_module+0x151/0x1ad
[  776.980018]  [<c106a12e>] ? do_munmap+0x183/0x19a
[  776.980018]  [<c1249777>] sysenter_do_call+0x12/0x26
[  776.980018] Code: a4 00 00 00 89 e5 e8 25 3b ff ff 5d c3 55 05 e0 00 00 00 89 e5 e8 16 3b ff ff 5d c3 55 8b 88 28 02 00 00 89 e5 8b 90 2c 02 00 00 
[  776.980018]  51 04 89 0a c7 80 28 02 00 00 00 01 10 00 c7 80 2c 02 00 00 
[  776.980018] EIP: [<c11845ea>] scsi_unregister+0xf/0x34 SS:ESP 0068:d8ca9f4c
[  776.980018] CR2: 0000000000000004
[  777.209807] ---[ end trace 3feb5860cd6a778d ]---

It seems list_del gets NULL shost->sht_legacy_list.

scsi_register is never called, this seems to be the reason why 
sht_legacy_list is not filled?

-- 
Meelis Roos (mroos@linux.ee)

[PATCH] dpt_i2o: fix module removal BUG

[Meelis Roos]

dpt_i2o rmmod fails with

BUG: unable to handle kernel NULL pointer dereference at 00000004

The reason is that legacy scsi_unregister() expects that legacy 
scsi_register() has been called before but this is not the case here. 
Driver has been mostly converted to newer style scsi registration, so 
scsi_host_put() is needed instead of scsi_unregister().

Also deletes obsolete comments around the fix.

Tested with DPT SmartRAID V with several module insertions and 
removals.

Signed-off-by: Meelis Roos <mroos@linux.ee>

diff --git a/drivers/scsi/dpt_i2o.c b/drivers/scsi/dpt_i2o.c
index b4f6c9a..1f3df55 100644
--- a/drivers/scsi/dpt_i2o.c
+++ b/drivers/scsi/dpt_i2o.c
@@ -299,15 +299,11 @@ rebuild_sys_tab:
 }
 
 
-/*
- * scsi_unregister will be called AFTER we return.
- */
 static int adpt_release(struct Scsi_Host *host)
 {
 	adpt_hba* pHba = (adpt_hba*) host->hostdata[0];
-//	adpt_i2o_quiesce_hba(pHba);
 	adpt_i2o_delete_hba(pHba);
-	scsi_unregister(host);
+	scsi_host_put(host);
 	return 0;
 }
 

-- 
Meelis Roos (mroos@linux.ee)