Re: [PATCH 2/3] scsi: pm8001: Fix use-after-free for aborted TMF sas_task

[Jinpu Wang]

On Thu, Jan 27, 2022 at 2:18 PM John Garry <john.garry@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
>
> 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.
Not I'm aware of, but microchip guys know better.
Thx John!
Acked-by: Jack Wang <jinpu.wang@xxxxxxxxx>
>
>  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;
>                 }
>
> --
> 2.26.2
>