[PATCH 6/6] scsi: hisi_sas: add check of device in hisi_sas_task_exec()

[John Garry]

From: Xiaofei Tan <tanxiao...@huawei.com>

Currently we don't check that device is not gone before
dereferencing it's elements in the function
hisi_sas_task_exec() (specifically, the DQ pointer).

This patch fixes this issue by filling in the DQ
pointer in hisi_sas_task_prep(), after we check
that the device pointer is still safe to
reference.

Signed-off-by: Xiaofei Tan <tanxiao...@huawei.com>
Signed-off-by: John Garry <john.ga...@huawei.com>
---
 drivers/scsi/hisi_sas/hisi_sas_main.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/hisi_sas/hisi_sas_main.c 
b/drivers/scsi/hisi_sas/hisi_sas_main.c
index a451625..39f694e 100644
--- a/drivers/scsi/hisi_sas/hisi_sas_main.c
+++ b/drivers/scsi/hisi_sas/hisi_sas_main.c
@@ -310,12 +310,13 @@ static void hisi_sas_slot_abort(struct work_struct *work)
                task->task_done(task);
 }
 
-static int hisi_sas_task_prep(struct sas_task *task, struct hisi_sas_dq *dq,
+static int hisi_sas_task_prep(struct sas_task *task,
+                             struct hisi_sas_dq **dq_pointer,
                              int is_tmf, struct hisi_sas_tmf_task *tmf,
                              int *pass)
 {
-       struct hisi_hba *hisi_hba = dq->hisi_hba;
        struct domain_device *device = task->dev;
+       struct hisi_hba *hisi_hba = dev_to_hisi_hba(device);
        struct hisi_sas_device *sas_dev = device->lldd_dev;
        struct hisi_sas_port *port;
        struct hisi_sas_slot *slot;
@@ -323,8 +324,9 @@ static int hisi_sas_task_prep(struct sas_task *task, struct 
hisi_sas_dq *dq,
        struct asd_sas_port *sas_port = device->port;
        struct device *dev = hisi_hba->dev;
        int dlvry_queue_slot, dlvry_queue, rc, slot_idx;
-       int  n_elem = 0, n_elem_req = 0, n_elem_resp = 0;
+       int n_elem = 0, n_elem_req = 0, n_elem_resp = 0;
        unsigned long flags, flags_dq;
+       struct hisi_sas_dq *dq;
        int wr_q_index;
 
        if (!sas_port) {
@@ -352,6 +354,8 @@ static int hisi_sas_task_prep(struct sas_task *task, struct 
hisi_sas_dq *dq,
                return -ECOMM;
        }
 
+       *dq_pointer = dq = sas_dev->dq;
+
        port = to_hisi_sas_port(sas_port);
        if (port && !port->port_attached) {
                dev_info(dev, "task prep: %s port%d not attach device\n",
@@ -520,22 +524,21 @@ static int hisi_sas_task_exec(struct sas_task *task, 
gfp_t gfp_flags,
        unsigned long flags;
        struct hisi_hba *hisi_hba = dev_to_hisi_hba(task->dev);
        struct device *dev = hisi_hba->dev;
-       struct domain_device *device = task->dev;
-       struct hisi_sas_device *sas_dev = device->lldd_dev;
-       struct hisi_sas_dq *dq = sas_dev->dq;
+       struct hisi_sas_dq *dq = NULL;
 
        if (unlikely(test_bit(HISI_SAS_REJECT_CMD_BIT, &hisi_hba->flags)))
                return -EINVAL;
 
        /* protect task_prep and start_delivery sequence */
-       rc = hisi_sas_task_prep(task, dq, is_tmf, tmf, &pass);
+       rc = hisi_sas_task_prep(task, &dq, is_tmf, tmf, &pass);
        if (rc)
                dev_err(dev, "task exec: failed[%d]!\n", rc);
 
-       spin_lock_irqsave(&dq->lock, flags);
-       if (likely(pass))
+       if (likely(pass)) {
+               spin_lock_irqsave(&dq->lock, flags);
                hisi_hba->hw->start_delivery(dq);
-       spin_unlock_irqrestore(&dq->lock, flags);
+               spin_unlock_irqrestore(&dq->lock, flags);
+       }
 
        return rc;
 }
-- 
1.9.1