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SubjectRe: [PATH v2] scsi: scsi_dh_rdac: Avoid crash during rdac_bus_attach
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On 2021/1/13 14:31, Ye Bin wrote:
> We get follow BUG_ON when 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
>
> BUG_ON 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;
>
> Test as follow steps:
> (1) Find IO error, remove disk;
> (2) Insert disk back;
> (3) trigger scan disk;
>
> There is race between rdac_bus_attach and rdac_bus_detach, maybe access
> rdac_dh_data which h->sdev has been set NULL when process rdac attach. And also
> find that "h->sdev" set value after add list, this may lead to reference NULL ptr.
>
> Signed-off-by: Ye Bin <yebin10@huawei.com>
> ---
> 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 5efc959493ec..85a71bafaea7 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);
> }
>
ping ...

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