scsi: libfc: Fix use after free in fc_exch_abts_resp()

[ Upstream commit 271add1 ]

fc_exch_release(ep) will decrease the ep's reference count. When the
reference count reaches zero, it is freed. But ep is still used in the
following code, which will lead to a use after free.

Return after the fc_exch_release() call to avoid use after free.

Link: https://lore.kernel.org/r/20220303015115.459778-1-niejianglei2021@163.com
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jianglei Nie <niejianglei2021@163.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Jianglei Nie

drivers/scsi/libfc/fc_exch.c

@@ -1701,6 +1701,7 @@ static void fc_exch_abts_resp(struct fc_exch *ep, struct fc_frame *fp)
 	if (cancel_delayed_work_sync(&ep->timeout_work)) {
 		FC_EXCH_DBG(ep, "Exchange timer canceled due to ABTS response\n");
 		fc_exch_release(ep);	/* release from pending timer hold */
+		return;
 	}
 
 	spin_lock_bh(&ep->ex_lock);