Re: net: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected in skb_array_produce

Michael S. Tsirkin
2017-02-09T17:58:31Z

On Thu, Feb 09, 2017 at 11:49:30AM +0100, Dmitry Vyukov wrote:
> On Thu, Feb 9, 2017 at 11:02 AM, Jason Wang <jasowang@redhat.com> wrote:
> >
> >
> > ----- Original Message -----
> >> Hello,
> >>
> >> I've got the following report while running syzkaller fuzzer on mmotm
> >> (git://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git)
> >> remotes/mmotm/auto-latest ee4ba7533626ba7bf2f8b992266467ac9fdc045e:
> >>
> >
> > [...]
> >
> >>
> >> other info that might help us debug this:
> >>
> >> Possible interrupt unsafe locking scenario:
> >>
> >> CPU0 CPU1
> >> ---- ----
> >> lock(&(&r->consumer_lock)->rlock);
> >> local_irq_disable();
> >> lock(&(&r->producer_lock)->rlock);
> >> lock(&(&r->consumer_lock)->rlock);
> >> <Interrupt>
> >> lock(&(&r->producer_lock)->rlock);
> >>
> >
> > Thanks a lot for the testing.
> >
> > Looks like we could address this by using skb_array_consume_bh() instead.
> >
> > Could you pls verify if the following patch works?
>
> No, I can't test it, sorry. This happened once on bots. And bots
> currently test only upstream versions.

Which trees are tested? Will linux-next help?

>
> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > index 8a7d6b9..a97c00d 100644
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -520,7 +520,7 @@ static void tun_queue_purge(struct tun_file *tfile)
> > {
> > struct sk_buff *skb;
> >
> > - while ((skb = skb_array_consume(&tfile->tx_array)) != NULL)
> > + while ((skb = skb_array_consume_bh(&tfile->tx_array)) != NULL)
> > kfree_skb(skb);
> >
> > skb_queue_purge(&tfile->sk.sk_write_queue);
> > @@ -1458,7 +1458,7 @@ static struct sk_buff *tun_ring_recv(struct tun_file *tfile, int noblock,
> > struct sk_buff *skb = NULL;
> > int error = 0;
> >
> > - skb = skb_array_consume(&tfile->tx_array);
> > + skb = skb_array_consume_bh(&tfile->tx_array);
> > if (skb)
> > goto out;
> > if (noblock) {
> > @@ -1470,7 +1470,7 @@ static struct sk_buff *tun_ring_recv(struct tun_file *tfile, int noblock,
> > current->state = TASK_INTERRUPTIBLE;
> >
> > while (1) {
> > - skb = skb_array_consume(&tfile->tx_array);
> > + skb = skb_array_consume_bh(&tfile->tx_array);
> > if (skb)
> > break;
> > if (signal_pending(current)) {
> >
> > --
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