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Date:	Thu, 17 Jan 2008 14:30:41 +0300
From:	Alexey Dobriyan <adobriyan@...ru>
To:	Daniel Lezcano <dlezcano@...ibm.com>
Cc:	davem@...emloft.net, den@...ru, netdev@...r.kernel.org,
	devel@...nvz.org
Subject: Re: Broken "Make ip6_frags per namespace" patch

On Thu, Jan 17, 2008 at 11:40:42AM +0100, Daniel Lezcano wrote:
> Alexey Dobriyan wrote:
> >>commit c064c4811b3e87ff8202f5a966ff4eea0bc54575
> >>Author: Daniel Lezcano <dlezcano@...ibm.com>
> >>Date:   Thu Jan 10 02:56:03 2008 -0800
> >>
> >>    [NETNS][IPV6]: Make ip6_frags per namespace.
> >>    
> >>    The ip6_frags is moved to the network namespace structure.  Because
> >>    there can be multiple instances of the network namespaces, and the
> >>    ip6_frags is no longer a global static variable, a helper function has
> >>    been added to facilitate the initialization of the variables.
> >>    
> >>    Until the ipv6 protocol is not per namespace, the variables are
> >>    accessed relatively from the initial network namespace.
> >
> >>--- a/include/net/netns/ipv6.h
> >>+++ b/include/net/netns/ipv6.h
> >
> >>@@ -11,6 +13,7 @@ struct netns_sysctl_ipv6 {
> >> #ifdef CONFIG_SYSCTL
> >> 	struct ctl_table_header *table;
> >> #endif
> >>+	struct inet_frags_ctl frags;
> >
> >>--- a/net/ipv6/reassembly.c
> >>+++ b/net/ipv6/reassembly.c
> >
> >>@@ -632,6 +625,11 @@ static struct inet6_protocol frag_protocol =
> >> 	.flags		=	INET6_PROTO_NOPOLICY,
> >> };
> >> 
> >>+void ipv6_frag_sysctl_init(struct net *net)
> >>+{
> >>+	ip6_frags.ctl = &net->ipv6.sysctl.frags;
> >>+}
> >
> >_This_ can't work. ip6frags is only one and ->ctl pointer is flipped
> >onto per-netns data. Changelog is also misleading: ip6_frags_ctl is
> >moved to netns not all ip6_frags.
> >
> >Oopsing place below -- f->ctl dereference in preparation of mod_timer() 
> >call.
> >
> >
> >
> >BUG: unable to handle kernel paging request at virtual address f5da8fc8
> >printing eip: c11d868a *pdpt = 0000000000003001 *pde = 0000000001728067 
> >*pte = 0000000035da8000 Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> >Modules linked in: ebt_ip ebt_dnat ebt_arpreply ebt_arp ebt_among 
> >ebtable_nat ip6t_REJECT ip6table_filter ip6_tables ebtable_filter 
> >ebtable_broute ebt_802_3 ebtables des_generic nf_conntrack_netbios_ns 
> >nf_conntrack_ipv4 xt_state nf_conntrack xt_tcpudp ipt_REJECT 
> >iptable_filter ip_tables deflate zlib_deflate zlib_inflate cryptomgr 
> >crypto_hash cpufreq_stats cpufreq_ondemand cdrom cbc bridge llc blkcipher 
> >crypto_algapi arpt_mangle arptable_filter arp_tables x_tables ah6 
> >af_packet ipv6
> >
> >Pid: 0, comm: swapper Not tainted (2.6.24-rc7-net-2.6.25-nf-sysfs-n #30)
> >EIP: 0060:[<c11d868a>] EFLAGS: 00010246 CPU: 1
> >EIP is at inet_frag_secret_rebuild+0xaa/0xd0
> >EAX: f5da8fbc EBX: 00000000 ECX: c1310000 EDX: 00000100
> >ESI: f7cba000 EDI: f898f7a0 EBP: 00000040 ESP: c1310f90
> > DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
> >Process swapper (pid: 0, ti=c1310000 task=f7c9a580 task.ti=f7c9b000)
> >Stack: f898f7a8 f898f8a8 000ddcbd f898f7a0 f7cba000 c1310fc4 00000100 
> >c1026d60 00000002 00000001 c1191183 c4779ddc c11d85e0 f898c860 
> >       f898c860 c12c4a88 00000001 c1308da0 0000000a c1023477 00000001 
> >       c130b640 c130b640 f7c9bf34 Call Trace:
> > [<c1026d60>] run_timer_softirq+0x120/0x190
> > [<c1191183>] net_rx_action+0x53/0x220
> > [<c11d85e0>] inet_frag_secret_rebuild+0x0/0xd0
> > [<c1023477>] __do_softirq+0x87/0x100
> > [<c10059cf>] do_softirq+0xaf/0x110
> > [<c10233e3>] irq_exit+0x83/0x90
> > [<c1010ce7>] smp_apic_timer_interrupt+0x57/0x90
> > [<c10036e1>] apic_timer_interrupt+0x29/0x38
> > [<c10036eb>] apic_timer_interrupt+0x33/0x38
> > [<c1001460>] default_idle+0x0/0x60
> > [<c10014a0>] default_idle+0x40/0x60
> > [<c1000ea3>] cpu_idle+0x73/0xb0
> >=======================
> >Code: 8b 10 85 d2 89 13 74 03 89 5a 04 89 18 89 43 04 85 f6 89 f3 75 bb 45 
> >83 fd 40 75 a5 8b 44 24 04 e8 4c 3f 01 00 8b 87 50 01 00 00 <8b> 50 0c 01 
> >54 24 08 8d 87 38 01 00 00 8b 54 24 08 83 c4 0c 5b EIP: [<c11d868a>] 
> >inet_frag_secret_rebuild+0xaa/0xd0 SS:ESP 0068:c1310f90
> >Kernel panic - not syncing: Fatal exception in interrupt
> 
> Hi Alexey,
> 
> does it happen after unsharing the network ?

Yep. clone(CLONE_NEWNET) in a loop and sooner or later you'll see this.

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