Re: [PATCH v2 1/1] xfrm : lock input tasklet skb queue

[Joerg Vehlow]

Hi,

I always expected this to be applied to the RT patches. That's why
I originally send my patch to to Sebastian, Thomas and Steven (I added
them again now. The website of the rt patches says patches for the
CONFIG_REEMPT_RT patchset should be send to lkml.

I hope one of the rt patch maintainers will reply here.

JÃrg

Am 24.10.2019 um 12:31 schrieb Steffen Klassert:
> On Tue, Oct 22, 2019 at 05:22:04PM -0700, Tom Rix wrote:
> > On PREEMPT_RT_FULL while running netperf, a corruption
> > of the skb queue causes an oops.
> >
> > This appears to be caused by a race condition here
> >          __skb_queue_tail(&trans->queue, skb);
> >          tasklet_schedule(&trans->tasklet);
> > Where the queue is changed before the tasklet is locked by
> > tasklet_schedule.
> >
> > The fix is to use the skb queue lock.
> >
> > This is the original work of Joerg Vehlow <joerg.vehlow@xxxxxxxxxxx>
> > https://lkml.org/lkml/2019/9/9/111
> >    xfrm_input: Protect queue with lock
> >
> >    During the skb_queue_splice_init the tasklet could have been preempted
> >    and __skb_queue_tail called, which led to an inconsistent queue.
> >
> > ifdefs for CONFIG_PREEMPT_RT_FULL added to reduce runtime effects
> > on the normal kernel.
> Has Herbert commented on your initial patch, please
> fix PREEMPT_RT_FULL instead. There are certainly many
> more codepaths that take such assumptions. You can not
> fix this by distributing a spin_lock_irqsave here
> and there.