[PATCH 5.13 013/127] scsi: scsi_dh_rdac: Avoid crash during rdac_bus_attach()

Sasha Levin
2021-08-24T16:56:52Z

From: Ye Bin <yebin10@huawei.com>

[ Upstream commit bc546c0c9abb3bb2fb46866b3d1e6ade9695a5f6 ]

The following BUG_ON() was observed during RDAC scan:

[595952.944297] kernel BUG at drivers/scsi/device_handler/scsi_dh_rdac.c:427!
[595952.951143] Internal error: Oops - BUG: 0 [#1] SMP
......
[595953.251065] Call trace:
[595953.259054] check_ownership+0xb0/0x118
[595953.269794] rdac_bus_attach+0x1f0/0x4b0
[595953.273787] scsi_dh_handler_attach+0x3c/0xe8
[595953.278211] scsi_dh_add_device+0xc4/0xe8
[595953.282291] scsi_sysfs_add_sdev+0x8c/0x2a8
[595953.286544] scsi_probe_and_add_lun+0x9fc/0xd00
[595953.291142] __scsi_scan_target+0x598/0x630
[595953.295395] scsi_scan_target+0x120/0x130
[595953.299481] fc_user_scan+0x1a0/0x1c0 [scsi_transport_fc]
[595953.304944] store_scan+0xb0/0x108
[595953.308420] dev_attr_store+0x44/0x60
[595953.312160] sysfs_kf_write+0x58/0x80
[595953.315893] kernfs_fop_write+0xe8/0x1f0
[595953.319888] __vfs_write+0x60/0x190
[595953.323448] vfs_write+0xac/0x1c0
[595953.326836] ksys_write+0x74/0xf0
[595953.330221] __arm64_sys_write+0x24/0x30

Code is in check_ownership:

list_for_each_entry_rcu(tmp, &h->ctlr->dh_list, node) {
/* h->sdev should always be valid */
BUG_ON(!tmp->sdev);
tmp->sdev->access_state = access_state;
}

rdac_bus_attach
initialize_controller
list_add_rcu(&h->node, &h->ctlr->dh_list);
h->sdev = sdev;

rdac_bus_detach
list_del_rcu(&h->node);
h->sdev = NULL;

Fix the race between rdac_bus_attach() and rdac_bus_detach() where h->sdev
is NULL when processing the RDAC attach.

Link: https://lore.kernel.org/r/20210113063103.2698953-1-yebin10@huawei.com
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Ye Bin <yebin10@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/scsi/device_handler/scsi_dh_rdac.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_rdac.c b/drivers/scsi/device_handler/scsi_dh_rdac.c
index 25f6e1ac9e7b..66652ab409cc 100644
--- a/drivers/scsi/device_handler/scsi_dh_rdac.c
+++ b/drivers/scsi/device_handler/scsi_dh_rdac.c
@@ -453,8 +453,8 @@ static int initialize_controller(struct scsi_device *sdev,
if (!h->ctlr)
err = SCSI_DH_RES_TEMP_UNAVAIL;
else {
- list_add_rcu(&h->node, &h->ctlr->dh_list);
h->sdev = sdev;
+ list_add_rcu(&h->node, &h->ctlr->dh_list);
}
spin_unlock(&list_lock);
err = SCSI_DH_OK;
@@ -778,11 +778,11 @@ static void rdac_bus_detach( struct scsi_device *sdev )
spin_lock(&list_lock);
if (h->ctlr) {
list_del_rcu(&h->node);
- h->sdev = NULL;
kref_put(&h->ctlr->kref, release_controller);
}
spin_unlock(&list_lock);
sdev->handler_data = NULL;
+ synchronize_rcu();
kfree(h);
}

--
2.30.2