Fw: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500

Fw: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500

[Stephen Hemminger]

Begin forwarded message:

Date: Tue,  4 Sep 2012 16:06:06 +0000 (UTC)
From: bugzilla-daemon@bugzilla.kernel.org
To: shemminger@linux-foundation.org
Subject: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500


https://bugzilla.kernel.org/show_bug.cgi?id=47021

           Summary: kernel panic with l2tpv3 & mtu > 1500
           Product: Networking
           Version: 2.5
    Kernel Version: 3.2.28
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Other
        AssignedTo: shemminger@linux-foundation.org
        ReportedBy: a1bert@atlas.cz
        Regression: No


first l2tpv3 packet that enters physical device with MTU > 1500 causes kernel
panic

tunel created using:

l2tpv3tun add tunnel tunnel_id 1 peer_tunnel_id 1 encap udp udp_sport 5001
udp_dport 5001 local 192.168.1.1 remote 192.168.1.2

l2tpv3tun add session tunnel_id 1 session_id 1 peer_session_id 1 dev l2tpeth1


reproducible: always

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Re: Fw: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

On Tue, 2012-09-04 at 09:07 -0700, Stephen Hemminger wrote:
> 
> Begin forwarded message:
> 
> Date: Tue,  4 Sep 2012 16:06:06 +0000 (UTC)
> From: bugzilla-daemon@bugzilla.kernel.org
> To: shemminger@linux-foundation.org
> Subject: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500
> 
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=47021
> 
>            Summary: kernel panic with l2tpv3 & mtu > 1500
>            Product: Networking
>            Version: 2.5
>     Kernel Version: 3.2.28
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: Other
>         AssignedTo: shemminger@linux-foundation.org
>         ReportedBy: a1bert@atlas.cz
>         Regression: No
> 
> 
> first l2tpv3 packet that enters physical device with MTU > 1500 causes kernel
> panic
> 
> tunel created using:
> 
> l2tpv3tun add tunnel tunnel_id 1 peer_tunnel_id 1 encap udp udp_sport 5001
> udp_dport 5001 local 192.168.1.1 remote 192.168.1.2
> 
> l2tpv3tun add session tunnel_id 1 session_id 1 peer_session_id 1 dev l2tpeth1
> 
> 
> reproducible: always
> 

Seems following patch is needed, not sure if it helps

[PATCH] l2tp: fix a typo in l2tp_eth_dev_recv()

While investigating l2tp bug, I hit a bug in eth_type_trans(),
because not enough bytes were pulled in skb head.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/l2tp/l2tp_eth.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c
index f9ee74d..3bfb34a 100644
--- a/net/l2tp/l2tp_eth.c
+++ b/net/l2tp/l2tp_eth.c
@@ -153,7 +153,7 @@ static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb,
 		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
 	}
 
-	if (!pskb_may_pull(skb, sizeof(ETH_HLEN)))
+	if (!pskb_may_pull(skb, ETH_HLEN))
 		goto error;
 
 	secpath_reset(skb);

Re: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500

[Stephen Hemminger]

On Tue, 04 Sep 2012 21:52:14 +0200
Eric Dumazet <eric.dumazet@gmail.com> wrote:

> From: Eric Dumazet <edumazet@google.com>
> 
> On Tue, 2012-09-04 at 09:07 -0700, Stephen Hemminger wrote:
> > 
> > Begin forwarded message:
> > 
> > Date: Tue,  4 Sep 2012 16:06:06 +0000 (UTC)
> > From: bugzilla-daemon@bugzilla.kernel.org
> > To: shemminger@linux-foundation.org
> > Subject: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500
> > 
> > 
> > https://bugzilla.kernel.org/show_bug.cgi?id=47021
> > 
> >            Summary: kernel panic with l2tpv3 & mtu > 1500
> >            Product: Networking
> >            Version: 2.5
> >     Kernel Version: 3.2.28
> >           Platform: All
> >         OS/Version: Linux
> >               Tree: Mainline
> >             Status: NEW
> >           Severity: normal
> >           Priority: P1
> >          Component: Other
> >         AssignedTo: shemminger@linux-foundation.org
> >         ReportedBy: a1bert@atlas.cz
> >         Regression: No
> > 
> > 
> > first l2tpv3 packet that enters physical device with MTU > 1500 causes kernel
> > panic
> > 
> > tunel created using:
> > 
> > l2tpv3tun add tunnel tunnel_id 1 peer_tunnel_id 1 encap udp udp_sport 5001
> > udp_dport 5001 local 192.168.1.1 remote 192.168.1.2
> > 
> > l2tpv3tun add session tunnel_id 1 session_id 1 peer_session_id 1 dev l2tpeth1
> > 
> > 
> > reproducible: always
> > 
> 
> Seems following patch is needed, not sure if it helps
> 
> [PATCH] l2tp: fix a typo in l2tp_eth_dev_recv()
> 
> While investigating l2tp bug, I hit a bug in eth_type_trans(),
> because not enough bytes were pulled in skb head.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
>  net/l2tp/l2tp_eth.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c
> index f9ee74d..3bfb34a 100644
> --- a/net/l2tp/l2tp_eth.c
> +++ b/net/l2tp/l2tp_eth.c
> @@ -153,7 +153,7 @@ static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb,
>  		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
>  	}
>  
> -	if (!pskb_may_pull(skb, sizeof(ETH_HLEN)))
> +	if (!pskb_may_pull(skb, ETH_HLEN))
>  		goto error;

I guess nobody ever looked inside this code. That seems like an obvious bug.

Re: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500

[Eric Dumazet]

On Tue, 2012-09-04 at 12:54 -0700, Stephen Hemminger wrote:

> 
> I guess nobody ever looked inside this code. That seems like an obvious bug.

It seems that l2tp lacks ECN support as well.

Re: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500

[a1]

Thanks, it definitely helped, no more panics now...

jn

>>>
>>
>> Seems following patch is needed, not sure if it helps
>>
>> [PATCH] l2tp: fix a typo in l2tp_eth_dev_recv()
>>
>> While investigating l2tp bug, I hit a bug in eth_type_trans(),
>> because not enough bytes were pulled in skb head.
>>
>> Signed-off-by: Eric Dumazet <edumazet@google.com>
>> ---
>>  net/l2tp/l2tp_eth.c |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c
>> index f9ee74d..3bfb34a 100644
>> --- a/net/l2tp/l2tp_eth.c
>> +++ b/net/l2tp/l2tp_eth.c
>> @@ -153,7 +153,7 @@ static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb,
>>  		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
>>  	}
>>  
>> -	if (!pskb_may_pull(skb, sizeof(ETH_HLEN)))
>> +	if (!pskb_may_pull(skb, ETH_HLEN))
>>  		goto error;
> 
> I guess nobody ever looked inside this code. That seems like an obvious bug.
> 

Re: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500

[Eric Dumazet]

On Wed, 2012-09-05 at 09:45 +0200, a1 wrote:
> Thanks, it definitely helped, no more panics now...

It seems MTU of device is wrong, and lot of packets are fragmented...

Its currently 1488, but it really should be less than that (accounting
for the IP+UDP header)

I wonder if anybody ever used this code ?

Re: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 04 Sep 2012 21:52:14 +0200

> [PATCH] l2tp: fix a typo in l2tp_eth_dev_recv()
> 
> While investigating l2tp bug, I hit a bug in eth_type_trans(),
> because not enough bytes were pulled in skb head.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>

LoL, applied and queued up for -stable.