netdev - Re: Fw: [Bug 199109] New: pptp: kernel printk "recursion detected", and then reboot itself

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Date:   Thu, 15 Mar 2018 18:51:50 +0100
From:   Guillaume Nault <g.nault@...halink.fr>
To:     xuheng333@...o.com, Stephen Hemminger <stephen@...workplumber.org>
Cc:     xeb@...l.ru, netdev@...r.kernel.org
Subject: Re: Fw: [Bug 199109] New: pptp: kernel printk "recursion detected",
 and then reboot itself

On Wed, Mar 14, 2018 at 08:02:17AM -0700, Stephen Hemminger wrote:
> 
> 
> Begin forwarded message:
> 
> Date: Wed, 14 Mar 2018 06:56:09 +0000
> From: bugzilla-daemon@...zilla.kernel.org
> To: stephen@...workplumber.org
> Subject: [Bug 199109] New: pptp: kernel printk "recursion detected", and then reboot itself
> 
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=199109
> 
>             Bug ID: 199109
>            Summary: pptp: kernel printk "recursion detected", and then
>                     reboot itself
>            Product: Networking
>            Version: 2.5
>     Kernel Version: 4.9.77
>           Hardware: Mips32
>                 OS: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: high
>           Priority: P1
>          Component: IPV4
>           Assignee: stephen@...workplumber.org
>           Reporter: xuheng333@...o.com
>         Regression: No
> 
> Created attachment 274715
>   --> https://bugzilla.kernel.org/attachment.cgi?id=274715&action=edit  
> system log
> 
> Use openwrt LEDE, (gcc version 5.5.0 (OpenWrt GCC 5.5.0 r5932-9c4fe10) ).
> When use pptp, make WAN(eth1) down and then make WAN(eth1) up, pptp will redial
> itself. Do this in a loop.
> 
> After a while, kernel print "recursion detected" and "net_ratelimit: 49422
> callbacks suppressed", print this many times, then system reboot.
> 
> When add more printk in driver "driver/net/ppp/ppp_generic.c", fond it fall in
> loop in "static void __ppp_xmit_process(struct ppp *ppp)", which called by
> "static void __ppp_channel_push(struct channel *pch)". 
> __ppp_channel_push() locked ppp->xmit_recursion, and loop for long time( while
> (!ppp->xmit_pending && (skb = skb_dequeue(&ppp->file.xq))) ppp_send_frame(ppp,
> skb); ). Some other thread want to lock ppp->xmit_recursion, but failed.
> 
> 
Hi Xuheng,

Are you sure that your PPTP packets aren't routed back to your PPP
interface? What's the IP address of the PPTP server?

Regards,

Guillaume