scsi: qla2xxx: Fix unmap of already freed sgl

The sgl is freed in the target stack in target_release_cmd_kref() before
calling qlt_free_cmd() but there is an unmap of sgl in qlt_free_cmd() that
causes a panic if sgl is not yet DMA unmapped:

NIP dma_direct_unmap_sg+0xdc/0x180
LR  dma_direct_unmap_sg+0xc8/0x180
Call Trace:
 ql_dbg_prefix+0x68/0xc0 [qla2xxx] (unreliable)
 dma_unmap_sg_attrs+0x54/0xf0
 qlt_unmap_sg.part.19+0x54/0x1c0 [qla2xxx]
 qlt_free_cmd+0x124/0x1d0 [qla2xxx]
 tcm_qla2xxx_release_cmd+0x4c/0xa0 [tcm_qla2xxx]
 target_put_sess_cmd+0x198/0x370 [target_core_mod]
 transport_generic_free_cmd+0x6c/0x1b0 [target_core_mod]
 tcm_qla2xxx_complete_free+0x6c/0x90 [tcm_qla2xxx]

The sgl may be left unmapped in error cases of response sending.  For
instance, qlt_rdy_to_xfer() maps sgl and exits when session is being
deleted keeping the sgl mapped.

This patch removes use-after-free of the sgl and ensures that the sgl is
unmapped for any command that was not sent to firmware.

Link: https://lore.kernel.org/r/20211018122650.11846-1-d.bogdanov@yadro.com
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Dmitry Bogdanov <d.bogdanov@yadro.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qla2xxx/qla_target.c

@@ -3319,8 +3319,7 @@ int qlt_xmit_response(struct qla_tgt_cmd *cmd, int xmit_type,
 			"RESET-RSP online/active/old-count/new-count = %d/%d/%d/%d.\n",
 			vha->flags.online, qla2x00_reset_active(vha),
 			cmd->reset_count, qpair->chip_reset);
-		spin_unlock_irqrestore(qpair->qp_lock_ptr, flags);
-		return 0;
+		goto out_unmap_unlock;
 	}
 
 	/* Does F/W have an IOCBs for this request */
@@ -3445,10 +3444,6 @@ int qlt_rdy_to_xfer(struct qla_tgt_cmd *cmd)
 	prm.sg = NULL;
 	prm.req_cnt = 1;
 
-	/* Calculate number of entries and segments required */
-	if (qlt_pci_map_calc_cnt(&prm) != 0)
-		return -EAGAIN;
-
 	if (!qpair->fw_started || (cmd->reset_count != qpair->chip_reset) ||
 	    (cmd->sess && cmd->sess->deleted)) {
 		/*
@@ -3466,6 +3461,10 @@ int qlt_rdy_to_xfer(struct qla_tgt_cmd *cmd)
 		return 0;
 	}
 
+	/* Calculate number of entries and segments required */
+	if (qlt_pci_map_calc_cnt(&prm) != 0)
+		return -EAGAIN;
+
 	spin_lock_irqsave(qpair->qp_lock_ptr, flags);
 	/* Does F/W have an IOCBs for this request */
 	res = qlt_check_reserve_free_req(qpair, prm.req_cnt);
@@ -3870,9 +3869,6 @@ void qlt_free_cmd(struct qla_tgt_cmd *cmd)
 
 	BUG_ON(cmd->cmd_in_wq);
 
-	if (cmd->sg_mapped)
-		qlt_unmap_sg(cmd->vha, cmd);
-
 	if (!cmd->q_full)
 		qlt_decr_num_pend_cmds(cmd->vha);