Re: [PATCH 3/3] scsi: pm8001: Fix use-after-free for aborted SSP/STP sas_task

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 1/27/22 22:12, John Garry wrote:
> Currently a use-after-free may occur if a sas_task is aborted by the upper
> layer before we handle the IO completion in mpi_ssp_completion() or
> mpi_sata_completion().
> 
> In this case, the following are the two steps in handling those IO
> completions:
> - call complete() to inform the upper layer handler of completion of
>   the IO
> - release driver resources associated with the sas_task in
>   pm8001_ccb_task_free() call
> 
> When complete() is called, the upper layer may free the sas_task. As such,
> we should not touch the associated sas_task afterwards, but we do so in
> the pm8001_ccb_task_free() call.
> 
> Fix by swapping the complete() and pm8001_ccb_task_free() calls ordering.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
>  drivers/scsi/pm8001/pm80xx_hwi.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/pm8001/pm80xx_hwi.c b/drivers/scsi/pm8001/pm80xx_hwi.c
> index ce38a2298e75..1134e86ac928 100644
> --- a/drivers/scsi/pm8001/pm80xx_hwi.c
> +++ b/drivers/scsi/pm8001/pm80xx_hwi.c
> @@ -2185,9 +2185,9 @@ mpi_ssp_completion(struct pm8001_hba_info *pm8001_ha, void *piomb)
>  		pm8001_dbg(pm8001_ha, FAIL,
>  			   "task 0x%p done with io_status 0x%x resp 0x%x stat 0x%x but aborted by upper layer!\n",
>  			   t, status, ts->resp, ts->stat);
> +		pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
>  		if (t->slow_task)
>  			complete(&t->slow_task->completion);
> -		pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
>  	} else {
>  		spin_unlock_irqrestore(&t->task_state_lock, flags);
>  		pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
> @@ -2794,9 +2794,9 @@ mpi_sata_completion(struct pm8001_hba_info *pm8001_ha,
>  		pm8001_dbg(pm8001_ha, FAIL,
>  			   "task 0x%p done with io_status 0x%x resp 0x%x stat 0x%x but aborted by upper layer!\n",
>  			   t, status, ts->resp, ts->stat);
> +		pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
>  		if (t->slow_task)
>  			complete(&t->slow_task->completion);
> -		pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
>  	} else {
>  		spin_unlock_irqrestore(&t->task_state_lock, flags);
>  		spin_unlock_irqrestore(&circularQ->oq_lock,

Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

-- 
Damien Le Moal
Western Digital Research