Re: [EXT] Re: [PATCH 2/8] qla2xxx: klocwork - Fix potential null pointer dereference

[Bart Van Assche <bvanassche@xxxxxxx>]

On 5/31/23 04:43, Nilesh Javali wrote:
> We can prevent the crash and notify the occurrence of this
> rare case by adding warn_on like,
>
> +       WARN_ON_ONCE(!cur_dsd);
> +       if (cur_dsd) {
> +               cur_dsd->address = 0;
> +               cur_dsd->length = 0;
> +               cur_dsd++;
> +       }
>          cmd_pkt->control_flags |= cpu_to_le16(CF_DATA_SEG_DESCR_ENABLE);
>          return 0;
>   }

I think there is a much better solution: drop the new "if (cur_dsd) {" 
test and instead add the following code:

diff --git a/drivers/scsi/qla2xxx/qla_iocb.c 
b/drivers/scsi/qla2xxx/qla_iocb.c
index 6acfdcc48b16..a1675f056a5c 100644
--- a/drivers/scsi/qla2xxx/qla_iocb.c
+++ b/drivers/scsi/qla2xxx/qla_iocb.c
@@ -607,7 +607,8 @@ qla24xx_build_scsi_type_6_iocbs(srb_t *sp, struct 
cmd_type_6 *cmd_pkt,
 	put_unaligned_le32(COMMAND_TYPE_6, &cmd_pkt->entry_type);

 	/* No data transfer */
-	if (!scsi_bufflen(cmd) || cmd->sc_data_direction == DMA_NONE) {
+	if (!scsi_bufflen(cmd) || cmd->sc_data_direction == DMA_NONE ||
+	    tot_dsds == 0) {
 		cmd_pkt->byte_count = cpu_to_le32(0);
 		return 0;
 	}

Is the above change sufficient to suppress the Klocwork warning?

Thanks,

Bart.