[PATCH] scsi: qla2xxx: Fix fcport handling in session creation race

[Serhat Kumral <serhatkumral1@gmail.com>]

When a second WWPN lookup finds an existing fcport due to a race, the
driver continues using the newly allocated fcport instead of the existing
one, then frees it at the end of qla24xx_create_new_sess().

Smatch reports a use-after-free of pla in the trailing cleanup.
qlt_plogi_ack_unref() may have already freed pla, making the subsequent
list_del() and kmem_cache_free() invalid.

Fix this by switching to the existing fcport, freeing the
redundant newly allocated one, and removing the trailing cleanup.

Fixes: b5d1531260b9 ("scsi: qla2xxx: Fix slow mem alloc behind lock")
Assisted-by: LLM
Signed-off-by: Serhat Kumral <serhatkumral1@gmail.com>
---
smatch output:
- drivers/scsi/qla2xxx/qla_os.c:5627 qla24xx_create_new_sess() error: dereferencing freed memory 'pla' (line 5573)

 drivers/scsi/qla2xxx/qla_os.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/qla2xxx/qla_os.c b/drivers/scsi/qla2xxx/qla_os.c
index 3c412c7fb6fe..1231265365af 100644
--- a/drivers/scsi/qla2xxx/qla_os.c
+++ b/drivers/scsi/qla2xxx/qla_os.c
@@ -5456,9 +5456,9 @@ void qla24xx_create_new_sess(struct scsi_qla_host *vha, struct qla_work_evt *e)
 {
 	unsigned long flags;
 	fc_port_t *fcport =  NULL, *tfcp;
+	fc_port_t *conflict_fcport = NULL;
 	struct qlt_plogi_ack_t *pla =
 	    (struct qlt_plogi_ack_t *)e->u.new_sess.pla;
-	uint8_t free_fcport = 0;
 
 	ql_dbg(ql_dbg_disc, vha, 0xffff,
 	    "%s %d %8phC enter\n",
@@ -5529,7 +5529,9 @@ void qla24xx_create_new_sess(struct scsi_qla_host *vha, struct qla_work_evt *e)
 			    __func__, tfcp->port_name, tfcp->disc_state,
 			    tfcp->fw_login_state);
 
-			free_fcport = 1;
+			conflict_fcport = fcport;
+			fcport = tfcp;
+
 		} else {
 			list_add_tail(&fcport->list, &vha->vp_fcports);
 
@@ -5542,6 +5544,9 @@ void qla24xx_create_new_sess(struct scsi_qla_host *vha, struct qla_work_evt *e)
 	}
 	spin_unlock_irqrestore(&vha->hw->tgt.sess_lock, flags);
 
+	if (conflict_fcport)
+		qla2x00_free_fcport(conflict_fcport);
+
 	if (fcport) {
 		fcport->id_changed = 1;
 		fcport->scan_state = QLA_FCPORT_FOUND;
@@ -5620,14 +5625,6 @@ void qla24xx_create_new_sess(struct scsi_qla_host *vha, struct qla_work_evt *e)
 			}
 		}
 	}
-
-	if (free_fcport) {
-		qla2x00_free_fcport(fcport);
-		if (pla) {
-			list_del(&pla->list);
-			kmem_cache_free(qla_tgt_plogi_cachep, pla);
-		}
-	}
 }
 
 static void qla_sp_retry(struct scsi_qla_host *vha, struct qla_work_evt *e)
-- 
2.53.0