Re: [PATCH 2/3] scsi: pm8001: Fix use-after-free for aborted TMF 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 TMF sas_task is aborted before
> we handle the IO completion in mpi_ssp_completion(). The abort occurs due
> to timeout.
> 
> When the timeout occurs, the SAS_TASK_STATE_ABORTED flag is set and the
> sas_task is freed in pm8001_exec_internal_tmf_task().
> 
> However, if the IO completion occurs later, the IO completion still thinks
> that the sas_task is available. Fix this by clearing the ccb->task if
> the TMF times out - the IO completion handler does nothing if this pointer
> is cleared.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
> 
> Note: For hisi_sas driver we already do something similar. However there
> we also flush the completion queue interrupt to ensure that there is no
> race in clearing the task pointer. Please advise if/how something similar
> can be done here.
> 
>  drivers/scsi/pm8001/pm8001_sas.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/scsi/pm8001/pm8001_sas.c b/drivers/scsi/pm8001/pm8001_sas.c
> index 160ee8b228c9..32edda3e55c6 100644
> --- a/drivers/scsi/pm8001/pm8001_sas.c
> +++ b/drivers/scsi/pm8001/pm8001_sas.c
> @@ -769,8 +769,13 @@ static int pm8001_exec_internal_tmf_task(struct domain_device *dev,
>  		res = -TMF_RESP_FUNC_FAILED;
>  		/* Even TMF timed out, return direct. */
>  		if (task->task_state_flags & SAS_TASK_STATE_ABORTED) {
> +			struct pm8001_ccb_info *ccb = task->lldd_task;
> +
>  			pm8001_dbg(pm8001_ha, FAIL, "TMF task[%x]timeout.\n",
>  				   tmf->tmf);
> +
> +			if (ccb)
> +				ccb->task = NULL;
>  			goto ex_err;
>  		}
>  

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

-- 
Damien Le Moal
Western Digital Research