linux-kernel - [BUG] scsi: wd719x: accessing the data mapped to streaming DMA

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Message-ID: <31b8f8a6-78ea-b237-da62-07f62ddee842@tsinghua.edu.cn>
Date:   Sun, 2 Aug 2020 21:18:25 +0800
From:   Jia-Ju Bai <baijiaju@...nghua.edu.cn>
To:     jejb@...ux.ibm.com, martin.petersen@...cle.com, dewell@...ds.net,
        Juergen.Gaertner@...x.si.uni-hannover.de
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [BUG] scsi: wd719x: accessing the data mapped to streaming DMA

In wd719x_queuecommand(), "scb" is mapped to streaming DMA:
   scb->phys = dma_map_single(..., scb, ...);

Then "scb" is accessed at many places in this function, such as:
   scb->SCB_options |= WD719X_SCB_FLAGS_AUTO_REQUEST_SENSE;
   ...
   scb->data_length = 0;
   scb->data_p = 0;

These accesses may cause data inconsistency between CPU cache and hardware.

I am not sure how to properly fix this problem, and thus I only report it.

Best wishes,
Jia-Ju Bai