linux-kernel - Re: [PATCH v2] scsi: qedi: Fix use after free bug in qedi

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Date:   Thu, 20 Apr 2023 10:38:26 -0500
From:   Mike Christie <michael.christie@...cle.com>
To:     Zheng Wang <zyytlz.wz@....com>, njavali@...vell.com
Cc:     mrangankar@...vell.com, GR-QLogic-Storage-Upstream@...vell.com,
        jejb@...ux.ibm.com, martin.petersen@...cle.com,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        hackerzheng666@...il.com, 1395428693sheep@...il.com,
        alex000young@...il.com
Subject: Re: [PATCH v2] scsi: qedi: Fix use after free bug in qedi_remove due
 to race condition

On 4/12/23 10:34 PM, Zheng Wang wrote:
> In qedi_probe, it calls __qedi_probe, which bound &qedi->recovery_work
> with qedi_recovery_handler and bound &qedi->board_disable_work
> with qedi_board_disable_work.
> 
> When it calls qedi_schedule_recovery_handler, it will finally
> call schedule_delayed_work to start the work.
> 
> When we call qedi_remove to remove the driver, there
> may be a sequence as follows:
> 
> Fix it by finishing the work before cleanup in qedi_remove.
> 
> CPU0                  CPU1
> 
>                      |qedi_recovery_handler
> qedi_remove          |
>   __qedi_remove      |
> iscsi_host_free      |
> scsi_host_put        |
> //free shost         |
>                      |iscsi_host_for_each_session
>                      |//use qedi->shost
> 
> Fixes: 4b1068f5d74b ("scsi: qedi: Add MFW error recovery process")
> Signed-off-by: Zheng Wang <zyytlz.wz@....com>
> ---
> v2:
> - remove unnecessary comment suggested by Mike Christie and cancel the work
> after qedi_ops->stop and qedi_ops->ll2->stop which ensure there is no more
> work suggested by Manish Rangankar

Look ok to me now. Thanks.

Reviewed-by: Mike Christie <michael.christie@...cle.com>