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

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Date:   Fri, 28 Jan 2022 07:18:42 +0100
From:   Jinpu Wang <jinpu.wang@...os.com>
To:     John Garry <john.garry@...wei.com>
Cc:     jinpu.wang@...os.com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, damien.lemoal@...nsource.wdc.com,
        Ajish.Koshy@...rochip.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, Viswas.G@...rochip.com,
        chenxiang66@...ilicon.com
Subject: Re: [PATCH 3/3] scsi: pm8001: Fix use-after-free for aborted SSP/STP sas_task

On Thu, Jan 27, 2022 at 2:18 PM John Garry <john.garry@...wei.com> 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@...wei.com>
Thx John!
Acked-by: Jack Wang <jinpu.wang@...os.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,
> --
> 2.26.2
>