[PATCH] scsi: scsi_dh_rdac: Avoid crash when a disk attach failed

[Huang Cun]

When a disk fails to attach, the struct rdac_dh_data is released,
but it is not removed from the ctlr->dh_list. When attaching another
disk, the released rdac_dh_data will be accessed and the following
BUG_ON() may be observed:

[  414.696167] scsi 5:0:0:7: rdac: Attach failed (8)
...
[  423.615364] kernel BUG at drivers/scsi/device_handler/scsi_dh_rdac.c:427!
[  423.615731] invalid opcode: 0000 [#1] SMP NOPTI
...
[  423.623247] Call Trace:
[  423.623598]  rdac_bus_attach+0x203/0x4c0
[  423.623949]  ? scsi_dh_handler_attach+0x2d/0x90
[  423.624300]  scsi_dh_handler_attach+0x2d/0x90
[  423.624652]  scsi_sysfs_add_sdev+0x88/0x270
[  423.625004]  scsi_probe_and_add_lun+0xc47/0xd50
[  423.625354]  scsi_report_lun_scan+0x339/0x3b0
[  423.625705]  __scsi_scan_target+0xe9/0x220
[  423.626056]  scsi_scan_target+0xf6/0x100
[  423.626404]  fc_scsi_scan_rport+0xa5/0xb0
[  423.626757]  process_one_work+0x15e/0x3f0
[  423.627106]  worker_thread+0x4c/0x440
[  423.627453]  ? rescuer_thread+0x350/0x350
[  423.627804]  kthread+0xf8/0x130
[  423.628153]  ? kthread_destroy_worker+0x40/0x40
[  423.628509]  ret_from_fork+0x1f/0x40

Fixes: 1a5dc166cd88 ("scsi_dh_rdac: update 'access_state' field")
Signed-off-by: Huang Cun <huangcun@xxxxxxxxxxxxxx>
Signed-off-by: Ding Hui <dinghui@xxxxxxxxxxxxxx>
Cc: Donglin Peng <pengdonglin@xxxxxxxxxxxxxx>
---
 drivers/scsi/device_handler/scsi_dh_rdac.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/scsi/device_handler/scsi_dh_rdac.c b/drivers/scsi/device_handler/scsi_dh_rdac.c
index c5538645057a..9d487c2b7708 100644
--- a/drivers/scsi/device_handler/scsi_dh_rdac.c
+++ b/drivers/scsi/device_handler/scsi_dh_rdac.c
@@ -762,8 +762,10 @@ static int rdac_bus_attach(struct scsi_device *sdev)
 
 clean_ctlr:
 	spin_lock(&list_lock);
+	list_del_rcu(&h->node);
 	kref_put(&h->ctlr->kref, release_controller);
 	spin_unlock(&list_lock);
+	synchronize_rcu();
 
 failed:
 	kfree(h);
-- 
2.27.0