Fw: [Bug 199109] New: pptp: kernel printk "recursion detected", and then reboot itself
From: Stephen Hemminger <stephen@networkplumber.org>
Date: 2018-03-14 15:02:21
Begin forwarded message:
Date: Wed, 14 Mar 2018 06:56:09 +0000
From: bugzilla-daemon@bugzilla.kernel.org
To: stephen@networkplumber.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@networkplumber.org
Reporter: xuheng333@zoho.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.
static void __ppp_channel_push(struct channel *pch)
{
struct sk_buff *skb;
struct ppp *ppp;
spin_lock_bh(&pch->downl);
if (pch->chan) {
while (!skb_queue_empty(&pch->file.xq)) {
skb = skb_dequeue(&pch->file.xq);
if (!pch->chan->ops->start_xmit(pch->chan, skb)) {
/* put the packet back and try again later */
skb_queue_head(&pch->file.xq, skb);
break;
}
}
} else {
/* channel got deregistered */
skb_queue_purge(&pch->file.xq);
}
spin_unlock_bh(&pch->downl);
/* see if there is anything from the attached unit to be sent */
if (skb_queue_empty(&pch->file.xq)) {
ppp = pch->ppp;
if (ppp)
__ppp_xmit_process(ppp);
}
}
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