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 <t...@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);