[PATCH] scsi: pm8001: Fix use-after-free in pm8001_queue_command()

[Salomon Dushimirimana <salomondush@google.com>]

Commit e29c47fe8946 ("scsi: pm8001: Simplify pm8001_task_exec()")
refactors pm8001_queue_command(), however it introduces a potential
cause of a double free scenario when it changes the function to return
-ENODEV in case of phy down/device gone state.

In this path, pm8001_queue_command updates task status and calls
task_done to indicate to upper layer that the task has been handled.
However, this also frees the underlying sas task. A -ENODEV is then
returned to the caller. When libsas sas_ata_qc_issue receives this error
value, it assumes the task wasn't handled/queued by LLDD and proceeds to
clean up and free the task again, resulting in a double free.

Since pm8001_queue_command handles the sas task in this case, it should
return 0 to the caller indicating that the task has been handled.

Fixes: e29c47fe8946 ("scsi: pm8001: Simplify pm8001_task_exec()")
Signed-off-by: Salomon Dushimirimana <salomondush@google.com>
---
 drivers/scsi/pm8001/pm8001_sas.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/pm8001/pm8001_sas.c b/drivers/scsi/pm8001/pm8001_sas.c
index 6a8d35aea93a..0285ce6400dc 100644
--- a/drivers/scsi/pm8001/pm8001_sas.c
+++ b/drivers/scsi/pm8001/pm8001_sas.c
@@ -525,8 +525,8 @@ int pm8001_queue_command(struct sas_task *task, gfp_t gfp_flags)
 		} else {
 			task->task_done(task);
 		}
-		rc = -ENODEV;
-		goto err_out;
+		spin_unlock_irqrestore(&pm8001_ha->lock, flags);
+		return 0;
 	}
 
 	ccb = pm8001_ccb_alloc(pm8001_ha, pm8001_dev, task);
-- 
2.53.0.rc2.204.g2597b5adb4-goog