Hello,
On Thu, 22 Sep 2022 22:06:30 +0800 Jason Yan wrote:
> On 2022/9/20 22:42, Duoming Zhou wrote:
> > When executing SMP task failed, the smp_execute_task_sg()
> > calls del_timer() to delete the "slow_task->timer". However,
> > if the timer handler sas_task_internal_timedout() is running,
> > the del_timer() in smp_execute_task_sg() will not stop it
> > and the UAF bug will happen. The process is shown below:
> >
> > (thread 1) | (thread 2)
> > smp_execute_task_sg() | sas_task_internal_timedout()
> > ... |
> > del_timer() |
> > ... | ...
> > sas_free_task(task) |
> > kfree(task->slow_task) //FREE|
> > | task->slow_task->... //USE
> >
> > Fix by calling del_timer_sync() in smp_execute_task_sg(),
> > which makes sure the timer handler have finished before
> > the "task->slow_task" is deallocated.
> >
> > Fixes: 2908d778ab3e ("[SCSI] aic94xx: new driver")
> > Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
> > ---
> > drivers/scsi/libsas/sas_expander.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
> > index fa2209080cc..5ce25183010 100644
> > --- a/drivers/scsi/libsas/sas_expander.c
> > +++ b/drivers/scsi/libsas/sas_expander.c
> > @@ -67,7 +67,7 @@ static int smp_execute_task_sg(struct domain_device *dev,
> > res = i->dft->lldd_execute_task(task, GFP_KERNEL);
> >
> > if (res) {
> > - del_timer(&task->slow_task->timer);
> > + del_timer_sync(&task->slow_task->timer);
> > pr_notice("executing SMP task failed:%d\n", res);
> > break;
> > }
> >
>
> The timer should be triggered 10 seconds later. I am curious why we stay
> this long before del_timer().
I think the hacker may create a large number of hardware interrupts to
increase the delayed time.
> However this change looks good to me.
> Reviewed-by: Jason Yan <yanaijie@xxxxxxxxxx>
Thank you!
Best regards,
Duoming Zhou
