qla2xxx: ABTS cause double free of qla_tgt_cmd +.

Fix double free problem within qla2xxx driver where
current code prematurely free qla_tgt_cmd while firmware
still has the command.  When firmware release the command
after abort, the code attempt a second free as part of
command completion processing.

When TCM start the free process, NULL pointer was hit.

------
WARNING: CPU: 8 PID: 43613 at lib/list_debug.c:62 __list_del_entry+0x82/0xd0()
list_del corruption. next->prev should be ffff88082b5cfb08, but was 6b6b6b6b6b6b6b6b
CPU: 8 PID: 43613 Comm: kworker/8:0 Tainted: GF       W  O 3.13.0-rc3-nab_t10dif+ #6
Hardware name: HP ProLiant DL380p Gen8, BIOS P70 08/20/2012
Workqueue: events cache_reap
000000000000003e ffff88081b2e3c78 ffffffff815a051f 000000000000003e
ffff88081b2e3cc8 ffff88081b2e3cb8 ffffffff8104fc2c 0000000000000000
ffff88082b5cfb00 ffff88081c788d00 ffff88082b5d7200 ffff88082b5d3080
Call Trace:
[<ffffffff815a051f>] dump_stack+0x49/0x62
[<ffffffff8104fc2c>] warn_slowpath_common+0x8c/0xc0
[<ffffffff8104fd16>] warn_slowpath_fmt+0x46/0x50
[<ffffffff812b6592>] __list_del_entry+0x82/0xd0
[<ffffffff8106d48c>] process_one_work+0x12c/0x510
[<ffffffff8106d4d3>] ? process_one_work+0x173/0x510
[<ffffffff8106ebdf>] worker_thread+0x11f/0x3a0
[<ffffffff8106eac0>] ? manage_workers+0x170/0x170
[<ffffffff81074f26>] kthread+0xf6/0x120
[<ffffffff8109f103>] ? __lock_release+0x133/0x1b0
[<ffffffff81074e30>] ? __init_kthread_worker+0x70/0x70
[<ffffffff815aec2c>] ret_from_fork+0x7c/0xb0
[<ffffffff81074e30>] ? __init_kthread_worker+0x70/0x70
---[ end trace dfc05c3f7caf8ebe ]---
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: [<ffffffff8106d391>] process_one_work+0x31/0x510
-------
Signed-off-by: Quinn Tran <quinn.tran@qlogic.com>
Signed-off-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: Saurav Kashyap <saurav.kashyap@qlogic.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/scsi/qla2xxx/qla_target.c

@@ -2681,7 +2681,18 @@ static void qlt_send_term_exchange(struct scsi_qla_host *vha,
 	rc = __qlt_send_term_exchange(vha, cmd, atio);
 	spin_unlock_irqrestore(&vha->hw->hardware_lock, flags);
 done:
-	if (rc == 1) {
+	/*
+	 * Terminate exchange will tell fw to release any active CTIO
+	 * that's in FW posession and cleanup the exchange.
+	 *
+	 * "cmd->state == QLA_TGT_STATE_ABORTED" means CTIO is still
+	 * down at FW.  Free the cmd later when CTIO comes back later
+	 * w/aborted(0x2) status.
+	 *
+	 * "cmd->state != QLA_TGT_STATE_ABORTED" means CTIO is already
+	 * back w/some err.  Free the cmd now.
+	 */
+	if ((rc == 1) && (cmd->state != QLA_TGT_STATE_ABORTED)) {
 		if (!ha_locked && !in_interrupt())
 			msleep(250); /* just in case */
 
@@ -2689,6 +2700,7 @@ static void qlt_send_term_exchange(struct scsi_qla_host *vha,
 			qlt_unmap_sg(vha, cmd);
 		vha->hw->tgt.tgt_ops->free_cmd(cmd);
 	}
+	return;
 }
 
 void qlt_free_cmd(struct qla_tgt_cmd *cmd)
@@ -2906,6 +2918,7 @@ static void qlt_do_ctio_completion(struct scsi_qla_host *vha, uint32_t handle,
 		case CTIO_LIP_RESET:
 		case CTIO_TARGET_RESET:
 		case CTIO_ABORTED:
+			/* driver request abort via Terminate exchange */
 		case CTIO_TIMEOUT:
 		case CTIO_INVALID_RX_ID:
 			/* They are OK */
@@ -2974,10 +2987,19 @@ static void qlt_do_ctio_completion(struct scsi_qla_host *vha, uint32_t handle,
 			break;
 		}
 
-		if (cmd->state != QLA_TGT_STATE_NEED_DATA)
+
+		/* "cmd->state == QLA_TGT_STATE_ABORTED" means
+		 * cmd is already aborted/terminated, we don't
+		 * need to terminate again.  The exchange is already
+		 * cleaned up/freed at FW level.  Just cleanup at driver
+		 * level.
+		 */
+		if ((cmd->state != QLA_TGT_STATE_NEED_DATA) &&
+			(cmd->state != QLA_TGT_STATE_ABORTED)) {
 			if (qlt_term_ctio_exchange(vha, ctio, cmd, status))
 				return;
 		}
+	}
 skip_term:
 
 	if (cmd->state == QLA_TGT_STATE_PROCESSED) {
@@ -3007,7 +3029,8 @@ static void qlt_do_ctio_completion(struct scsi_qla_host *vha, uint32_t handle,
 		    "not return a CTIO complete\n", vha->vp_idx, cmd->state);
 	}
 
-	if (unlikely(status != CTIO_SUCCESS)) {
+	if (unlikely(status != CTIO_SUCCESS) &&
+		(cmd->state != QLA_TGT_STATE_ABORTED)) {
 		ql_dbg(ql_dbg_tgt_mgt, vha, 0xf01f, "Finishing failed CTIO\n");
 		dump_stack();
 	}