Messages in this thread | | | Subject | Re: [PATCH 5/5] scsi: libsas: fix a race condition when smp task timeout | From | Jason Yan <> | Date | Wed, 19 Sep 2018 10:49:06 +0800 |
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On 2018/9/17 17:47, John Garry wrote: > 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() >
OK
>> 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. >
Is it necessary to add a variable just for consistency with other places?
>> + } >> 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. >
This changes the logic a bit. To be safe, maybe we shall do this with another patch after some tests.
>> >> > > Thanks, > John > > > > . >
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