scsi: target: Factor out a new helper, target_cmd_init_cdb()

target_setup_cmd_from_cdb() is called after a successful call to
transport_lookup_cmd_lun(). The new helper factors out the code that can be
called before the call to transport_lookup_cmd_lun(). This helper will be
used in an upcoming commit to address NULL pointer dereference.

Link: https://lore.kernel.org/r/1591559913-8388-2-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>

Author: ssudhakarp

drivers/target/target_core_transport.c

@@ -1410,11 +1410,8 @@ transport_check_alloc_task_attr(struct se_cmd *cmd)
 }
 
 sense_reason_t
-target_setup_cmd_from_cdb(struct se_cmd *cmd, unsigned char *cdb)
+target_cmd_init_cdb(struct se_cmd *cmd, unsigned char *cdb)
 {
-	struct se_device *dev = cmd->se_dev;
-	sense_reason_t ret;
-
 	/*
 	 * Ensure that the received CDB is less than the max (252 + 8) bytes
 	 * for VARIABLE_LENGTH_CMD
@@ -1448,6 +1445,17 @@ target_setup_cmd_from_cdb(struct se_cmd *cmd, unsigned char *cdb)
 	memcpy(cmd->t_task_cdb, cdb, scsi_command_size(cdb));
 
 	trace_target_sequencer_start(cmd);
+	return 0;
+}
+EXPORT_SYMBOL(target_cmd_init_cdb);
+
+sense_reason_t
+target_setup_cmd_from_cdb(struct se_cmd *cmd, unsigned char *cdb)
+{
+	struct se_device *dev = cmd->se_dev;
+	sense_reason_t ret;
+
+	target_cmd_init_cdb(cmd, cdb);
 
 	ret = dev->transport->parse_cdb(cmd);
 	if (ret == TCM_UNSUPPORTED_SCSI_OPCODE)

include/target/target_core_fabric.h

@@ -152,6 +152,7 @@ void	transport_init_se_cmd(struct se_cmd *,
 		const struct target_core_fabric_ops *,
 		struct se_session *, u32, int, int, unsigned char *);
 sense_reason_t transport_lookup_cmd_lun(struct se_cmd *, u64);
+sense_reason_t target_cmd_init_cdb(struct se_cmd *, unsigned char *);
 sense_reason_t target_setup_cmd_from_cdb(struct se_cmd *, unsigned char *);
 int	target_submit_cmd_map_sgls(struct se_cmd *, struct se_session *,
 		unsigned char *, unsigned char *, u64, u32, int, int, int,