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

Dmitry Vyukov
2017-02-09T10:58:58Z

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.

> 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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