Subject: Re: mISDN: WARNING: at kernel/softirq.c:124 local_bh_enable+0x8f/0xb0()

From: Mathias Kretschmer <[email-masked]>
Date: Tue, 23 Jun 2009 00:37:41 +0200

Hi Karsten,

applied your patch. Not sure if it fixed anything, though.
Attached is another call trace which looks slightly different.

Cheers,

Mathias

On Tuesday 09 June 2009 15:05:31 Karsten Keil wrote:
> On Freitag, 5. Juni 2009 12:01:03 Karsten Keil wrote:
> > Hi,
> >
> > I'm currently see this too from time to time, but have no idea about it.
>
> ...
>
> > > > [88563.318126] ------------[ cut here ]------------
> > > > [88563.318129] WARNING: at kernel/softirq.c:124
> > > > local_bh_enable+0x8f/0xb0() [88563.318130] Hardware name: empty
> > > > [88563.318132] Modules linked in: usbtouchscreen dvb_usb_cinergyT2
> > > > dummy bonding snd_emu10k1 snd_rawmidi snd_ac97_codec ath9k ac97_bus
> > > > snd_pcm snd_page_alloc snd_util_mem forcedeth snd_hwdep
> > > > [88563.318141] Pid: 826, comm: mISDN_hfc-pci.1 Not tainted
> > > > 2.6.29.4-grsec #13 [88563.318142] Call Trace:
> > > > [88563.318147]  [<ffffffff8025909a>] warn_slowpath+0xea/0x160
> > > > [88563.318149]  [<ffffffff8025ee0f>] local_bh_enable+0x8f/0xb0
> > > > [88563.318152]  [<ffffffff8065f284>] sk_filter+0x44/0xa0
> > > > [88563.318154]  [<ffffffff8064548d>] sock_queue_rcv_skb+0x5d/0x120
> > > > [88563.318156]  [<ffffffff8060410f>] mISDN_send+0x4f/0xa0
> > > > [88563.318159]  [<ffffffff8060790e>] l2up_create+0x7e/0x100
> > > > [88563.318161]  [<ffffffff8060b6e0>] l2_got_tei+0x0/0x90
> > > > [88563.318163]  [<ffffffff8060b722>] l2_got_tei+0x42/0x90
> > > > [88563.318164]  [<ffffffff80602d32>] mISDN_FsmEvent+0x82/0x100
> > > > [88563.318167]  [<ffffffff8060cb00>] tei_id_assign+0x0/0x120
> > > > [88563.318168]  [<ffffffff80602d32>] mISDN_FsmEvent+0x82/0x100
> > > > [88563.318170]  [<ffffffff8060e373>] mgr_send+0x4d3/0x660
>
> OK found it, it was in a inlined function call ph_data_ind() in mgr_send().
>
> This patch should fix it (will send it upstream later).
>
>
> From: Karsten Keil <[email-masked]>
> Date: Tue, 9 Jun 2009 14:38:39 +0200
> Subject: [PATCH] mISDN: Do not disable IRQ in ph_data_ind()
>
>
> This fix triggering the WARN_ON_ONCE(in_irq() || irqs_disabled()); in
> local_bh_enable().
>
> Here is no need to grab this lock, this was wrong at all and may
> cause a deadlock and access to freed memory, since on a TEI remove
> the current listelement can be deleted under us. So this is clearly
> a case for list_for_each_entry_safe.
>
> Signed-off-by: Karsten Keil <[email-masked]>
> ---
>  drivers/isdn/mISDN/tei.c |    7 ++-----
>  1 files changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/isdn/mISDN/tei.c b/drivers/isdn/mISDN/tei.c
> index bfcdd97..e04bad6 100644
> --- a/drivers/isdn/mISDN/tei.c
> +++ b/drivers/isdn/mISDN/tei.c
> @@ -862,8 +862,7 @@ static int
>  ph_data_ind(struct manager *mgr, struct sk_buff *skb)
>  {
>  	int		ret = -EINVAL;
> -	struct layer2	*l2;
> -	u_long		flags;
> +	struct layer2	*l2, *nl2;
>  	u_char		mt;
>
>  	if (skb->len < 8) {
> @@ -908,11 +907,9 @@ ph_data_ind(struct manager *mgr, struct sk_buff *skb)
>  		new_tei_req(mgr, &skb->data[4]);
>  		goto done;
>  	}
> -	read_lock_irqsave(&mgr->lock, flags);
> -	list_for_each_entry(l2, &mgr->layer2, list) {
> +	list_for_each_entry_safe(l2, nl2, &mgr->layer2, list) {
>  		tei_ph_data_ind(l2->tm, mt, &skb->data[4], skb->len - 4);
>  	}
> -	read_unlock_irqrestore(&mgr->lock, flags);
>  done:
>  	return ret;
>  }