[PATCH 3/3] scsi: pm8001: Fix use-after-free for aborted SSP/STP sas_task

[John Garry <john.garry@huawei.com>]

Currently a use-after-free may occur if a sas_task is aborted by the upper
layer before we handle the IO completion in mpi_ssp_completion() or
mpi_sata_completion().

In this case, the following are the two steps in handling those IO
completions:
- call complete() to inform the upper layer handler of completion of
  the IO
- release driver resources associated with the sas_task in
  pm8001_ccb_task_free() call

When complete() is called, the upper layer may free the sas_task. As such,
we should not touch the associated sas_task afterwards, but we do so in
the pm8001_ccb_task_free() call.

Fix by swapping the complete() and pm8001_ccb_task_free() calls ordering.

Signed-off-by: John Garry <john.garry@huawei.com>
---
 drivers/scsi/pm8001/pm80xx_hwi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/pm8001/pm80xx_hwi.c b/drivers/scsi/pm8001/pm80xx_hwi.c
index ce38a2298e75..1134e86ac928 100644
--- a/drivers/scsi/pm8001/pm80xx_hwi.c
+++ b/drivers/scsi/pm8001/pm80xx_hwi.c
@@ -2185,9 +2185,9 @@ mpi_ssp_completion(struct pm8001_hba_info *pm8001_ha, void *piomb)
 		pm8001_dbg(pm8001_ha, FAIL,
 			   "task 0x%p done with io_status 0x%x resp 0x%x stat 0x%x but aborted by upper layer!\n",
 			   t, status, ts->resp, ts->stat);
+		pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
 		if (t->slow_task)
 			complete(&t->slow_task->completion);
-		pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
 	} else {
 		spin_unlock_irqrestore(&t->task_state_lock, flags);
 		pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
@@ -2794,9 +2794,9 @@ mpi_sata_completion(struct pm8001_hba_info *pm8001_ha,
 		pm8001_dbg(pm8001_ha, FAIL,
 			   "task 0x%p done with io_status 0x%x resp 0x%x stat 0x%x but aborted by upper layer!\n",
 			   t, status, ts->resp, ts->stat);
+		pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
 		if (t->slow_task)
 			complete(&t->slow_task->completion);
-		pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
 	} else {
 		spin_unlock_irqrestore(&t->task_state_lock, flags);
 		spin_unlock_irqrestore(&circularQ->oq_lock,
-- 
2.26.2