Messages in this thread | | | Subject | Re: [PATCH 5/5] scsi: libsas: fix a race condition when smp task timeout | From | John Garry <> | Date | Mon, 17 Sep 2018 10:47:16 +0100 |
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On 12/09/2018 09:29, Jason Yan wrote: > When the lldd is processing the complete sas task in interrupt and set > the task stat as SAS_TASK_STATE_DONE, the smp timeout timer is able to > be triggered at the same time. And smp_task_timedout() will complete the > task wheter the SAS_TASK_STATE_DONE is set or not. Then the sas task may > freed before lldd end the interrupt process. Thus a use-after-free will > happen. > > Fix this by calling the complete() only when SAS_TASK_STATE_DONE is not > set. And remove the check of the return value of the del_timer(). >
Hi Jason,
Please mention that once the LLDD sets DONE, it must call task->done(), which will call smp_task_done()->complete()
> Reported-by: chenxiang <chenxiang66@hisilicon.com> > Signed-off-by: Jason Yan <yanaijie@huawei.com> > CC: John Garry <john.garry@huawei.com> > CC: Johannes Thumshirn <jthumshirn@suse.de> > CC: Ewan Milne <emilne@redhat.com> > CC: Christoph Hellwig <hch@lst.de> > CC: Tomas Henzl <thenzl@redhat.com> > CC: Dan Williams <dan.j.williams@intel.com> > CC: Hannes Reinecke <hare@suse.com> > --- > drivers/scsi/libsas/sas_expander.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c > index 52222940d398..0d1f72752ca2 100644 > --- a/drivers/scsi/libsas/sas_expander.c > +++ b/drivers/scsi/libsas/sas_expander.c > @@ -48,17 +48,16 @@ static void smp_task_timedout(struct timer_list *t) > unsigned long flags; > > spin_lock_irqsave(&task->task_state_lock, flags); > - if (!(task->task_state_flags & SAS_TASK_STATE_DONE)) > + if (!(task->task_state_flags & SAS_TASK_STATE_DONE)) { > task->task_state_flags |= SAS_TASK_STATE_ABORTED; > + complete(&task->slow_task->completion);
Nit: for consistency with any other time we use this lock, can we call complete() outside the lock? Maybe just use a flag variable for this.
> + } > spin_unlock_irqrestore(&task->task_state_lock, flags); > - > - complete(&task->slow_task->completion); > } > > static void smp_task_done(struct sas_task *task) > { > - if (!del_timer(&task->slow_task->timer)) > - return; > + del_timer(&task->slow_task->timer); > complete(&task->slow_task->completion); > }
Do we also need this change or similar: static int smp_execute_task_sg(struct domain_device *dev, if ((task->task_state_flags & SAS_TASK_STATE_ABORTED)) { SAS_DPRINTK("smp task timed out or aborted\n"); i->dft->lldd_abort_task(task); - if (!(task->task_state_flags & SAS_TASK_STATE_DONE)) { - SAS_DPRINTK("SMP task aborted and not done\n"); - break; - } + break;
To me, the ABORTED and DONE states are mutually exclusive.
> >
Thanks, John
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