Messages in this thread | | | Subject | Re: [PATCH] xfrm : lock input tasklet skb queue | From | Joerg Vehlow <> | Date | Tue, 22 Oct 2019 10:58:44 +0200 |
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Hi,
I already send a patch on 2019-09-09 to this mailing list with a similar issue[1]. Sadly no replies, although this is a huge bug in the rt kernel. I fixed it a bit differently, using smaller locked regions. You have also propably a bug in your patch, because trans->queue.lock is no initialized by __skb_queue_head_init (in xfrm_input_init)
Jörg
[1] https://lkml.org/lkml/2019/9/9/111
Am 20.10.2019 um 17:46 schrieb Tom Rix: > 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. > > Signed-off-by: Tom Rix <trix@redhat.com> > --- > net/xfrm/xfrm_input.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c > index 9b599ed66d97..226dead86828 100644 > --- a/net/xfrm/xfrm_input.c > +++ b/net/xfrm/xfrm_input.c > @@ -758,12 +758,16 @@ static void xfrm_trans_reinject(unsigned long data) > struct xfrm_trans_tasklet *trans = (void *)data; > struct sk_buff_head queue; > struct sk_buff *skb; > + unsigned long flags; > > __skb_queue_head_init(&queue); > + spin_lock_irqsave(&trans->queue.lock, flags); > skb_queue_splice_init(&trans->queue, &queue); > > while ((skb = __skb_dequeue(&queue))) > XFRM_TRANS_SKB_CB(skb)->finish(dev_net(skb->dev), NULL, skb); > + > + spin_unlock_irqrestore(&trans->queue.lock, flags); > } > > int xfrm_trans_queue(struct sk_buff *skb, > @@ -771,15 +775,20 @@ int xfrm_trans_queue(struct sk_buff *skb, > struct sk_buff *)) > { > struct xfrm_trans_tasklet *trans; > + unsigned long flags; > > trans = this_cpu_ptr(&xfrm_trans_tasklet); > + spin_lock_irqsave(&trans->queue.lock, flags); > > - if (skb_queue_len(&trans->queue) >= netdev_max_backlog) > + if (skb_queue_len(&trans->queue) >= netdev_max_backlog) { > + spin_unlock_irqrestore(&trans->queue.lock, flags); > return -ENOBUFS; > + } > > XFRM_TRANS_SKB_CB(skb)->finish = finish; > __skb_queue_tail(&trans->queue, skb); > tasklet_schedule(&trans->tasklet); > + spin_unlock_irqrestore(&trans->queue.lock, flags); > return 0; > } > EXPORT_SYMBOL(xfrm_trans_queue);
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