scsi: target: Fix NULL pointer dereference

NULL pointer dereference happens when the following conditions are met:

1) A SCSI command is received for a non-existing LU or cdb initialization
   fails in target_setup_cmd_from_cdb().

2) Tracing is enabled.

The following call sequences lead to NULL pointer dereference:

1) iscsit_setup_scsi_cmd
     transport_lookup_cmd_lun <-- lookup fails.
          or
     target_setup_cmd_from_cdb() <-- cdb initialization fails
   iscsit_process_scsi_cmd
     iscsit_sequence_cmd
       transport_send_check_condition_and_sense
         trace_target_cmd_complete <-- NULL dereference

2) target_submit_cmd_map_sgls
     transport_lookup_cmd_lun <-- lookup fails
          or
     target_setup_cmd_from_cdb() <-- cdb initialization fails
       transport_send_check_condition_and_sense
         trace_target_cmd_complete <-- NULL dereference

In the above sequence, cmd->t_task_cdb is uninitialized which when
referenced in trace_target_cmd_complete() causes NULL pointer dereference.

The fix is to use the helper, target_cmd_init_cdb() and call it after
transport_init_se_cmd() is called, so that cmd->t_task_cdb can be
initialized and hence can be referenced in trace_target_cmd_complete().

Link: https://lore.kernel.org/r/1591559913-8388-4-git-send-email-sudhakar.panneerselvam@oracle.com
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Sudhakar Panneerselvam <sudhakar.panneerselvam@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 11 insertions, 7 deletions

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 1b453629b516..93534dcc66c9 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -1167,6 +1167,16 @@ int iscsit_setup_scsi_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
 
 	target_get_sess_cmd(&cmd->se_cmd, true);
 
+	cmd->sense_reason = target_cmd_init_cdb(&cmd->se_cmd, hdr->cdb);
+	if (cmd->sense_reason) {
+		if (cmd->sense_reason == TCM_OUT_OF_RESOURCES) {
+			return iscsit_add_reject_cmd(cmd,
+				ISCSI_REASON_BOOKMARK_NO_RESOURCES, buf);
+		}
+
+		goto attach_cmd;
+	}
+
 	cmd->sense_reason = transport_lookup_cmd_lun(&cmd->se_cmd);
 	if (cmd->sense_reason)
 		goto attach_cmd;
@@ -1174,14 +1184,8 @@ int iscsit_setup_scsi_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
 	/* only used for printks or comparing with ->ref_task_tag */
 	cmd->se_cmd.tag = (__force u32)cmd->init_task_tag;
 	cmd->sense_reason = target_setup_cmd_from_cdb(&cmd->se_cmd, hdr->cdb);
-	if (cmd->sense_reason) {
-		if (cmd->sense_reason == TCM_OUT_OF_RESOURCES) {
-			return iscsit_add_reject_cmd(cmd,
-					ISCSI_REASON_BOOKMARK_NO_RESOURCES, buf);
-		}
-
+	if (cmd->sense_reason)
 		goto attach_cmd;
-	}
 
 	if (iscsit_build_pdu_and_seq_lists(cmd, payload_length) < 0) {
 		return iscsit_add_reject_cmd(cmd,