scsi: target: iscsi: Fix use-after-free in iscsit_dec_conn_usage_count()

In iscsit_dec_conn_usage_count(), the function calls complete() while
holding the conn->conn_usage_lock. As soon as complete() is invoked, the
waiter (such as iscsit_close_connection()) may wake up and proceed to free
the iscsit_conn structure.

If the waiter frees the memory before the current thread reaches
spin_unlock_bh(), it results in a KASAN slab-use-after-free as the function
attempts to release a lock within the already-freed connection structure.

Fix this by releasing the spinlock before calling complete().

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Reported-by: Zhaojuan Guo <zguo@redhat.com>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Link: https://patch.msgid.link/20260112165352.138606-2-mlombard@redhat.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c
index 5e6cf34929b55bf351d4cb2c050d22be5a6ea7c0..3319394bf542c48ce61fd00a70f24f28272b5955 100644 (file)
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -810,8 +810,11 @@ void iscsit_dec_conn_usage_count(struct iscsit_conn *conn)
        spin_lock_bh(&conn->conn_usage_lock);
        conn->conn_usage_count--;
 
-       if (!conn->conn_usage_count && conn->conn_waiting_on_uc)
+       if (!conn->conn_usage_count && conn->conn_waiting_on_uc) {
+               spin_unlock_bh(&conn->conn_usage_lock);
                complete(&conn->conn_waiting_on_uc_comp);
+               return;
+       }
 
        spin_unlock_bh(&conn->conn_usage_lock);
 }