[PATCH] net/bridge: Add missing in6_dev_put in br_validate_ipv6

[PATCH] net/bridge: Add missing in6_dev_put in br_validate_ipv6

[Julien Grall]

The commit efb6de9b4ba0092b2c55f6a52d16294a8a698edd "netfilter: bridge:
forward IPv6 fragmented packets" introduced a new function
br_validate_ipv6 which take a reference on the inet6 device. Although,
the reference is not released at the end.

This will result to the impossibility to destroy any netdevice using
ipv6 and bridge.

Spotted while trying to destroy a Xen guest on the upstream Linux:
"unregister_netdevice: waiting for vif1.0 to become free. Usage count = 1"

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Cc: Bernhard Thaler <bernhard.thaler@wvnet.at>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: fw@strlen.de
Cc: ian.campbell@citrix.com
Cc: wei.liu2@citrix.com

---
    Note that it's impossible to create new guest after this message.
    I'm not sure if it's normal.
---
 net/bridge/br_netfilter_ipv6.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/bridge/br_netfilter_ipv6.c b/net/bridge/br_netfilter_ipv6.c
index 6d12d26..7046e19 100644
--- a/net/bridge/br_netfilter_ipv6.c
+++ b/net/bridge/br_netfilter_ipv6.c
@@ -140,11 +140,16 @@ int br_validate_ipv6(struct sk_buff *skb)
 	/* No IP options in IPv6 header; however it should be
 	 * checked if some next headers need special treatment
 	 */
+
+	in6_dev_put(idev);
+
 	return 0;
 
 inhdr_error:
 	IP6_INC_STATS_BH(dev_net(dev), idev, IPSTATS_MIB_INHDRERRORS);
 drop:
+	in6_dev_put(idev);
+
 	return -1;
 }
 
-- 
2.1.4

Re: [PATCH] net/bridge: Add missing in6_dev_put in br_validate_ipv6

[Florian Westphal]

Julien Grall <julien.grall@citrix.com> wrote:
> The commit efb6de9b4ba0092b2c55f6a52d16294a8a698edd "netfilter: bridge:
> forward IPv6 fragmented packets" introduced a new function
> br_validate_ipv6 which take a reference on the inet6 device. Although,
> the reference is not released at the end.
> 
> This will result to the impossibility to destroy any netdevice using
> ipv6 and bridge.
> 
> Spotted while trying to destroy a Xen guest on the upstream Linux:
> "unregister_netdevice: waiting for vif1.0 to become free. Usage count = 1"

Ugh :-/

I think it makes more sense to use __in6_dev_get() instead which doesn't
take a reference.

Re: [Xen-devel] [PATCH] net/bridge: Add missing in6_dev_put in br_validate_ipv6

[Bob Liu]

On 07/04/2015 02:01 AM, Julien Grall wrote:
> The commit efb6de9b4ba0092b2c55f6a52d16294a8a698edd "netfilter: bridge:
> forward IPv6 fragmented packets" introduced a new function
> br_validate_ipv6 which take a reference on the inet6 device. Although,
> the reference is not released at the end.
> 
> This will result to the impossibility to destroy any netdevice using
> ipv6 and bridge.
> 
> Spotted while trying to destroy a Xen guest on the upstream Linux:
> "unregister_netdevice: waiting for vif1.0 to become free. Usage count = 1"
> 
> Signed-off-by: Julien Grall <julien.grall@citrix.com>

Also hit the same issue, thank you for the fix.

Tested-by: Bob Liu <bob.liu@oracle.com>

> Cc: Bernhard Thaler <bernhard.thaler@wvnet.at>
> Cc: Pablo Neira Ayuso <pablo@netfilter.org>
> Cc: fw@strlen.de
> Cc: ian.campbell@citrix.com
> Cc: wei.liu2@citrix.com
> 
> ---
>     Note that it's impossible to create new guest after this message.
>     I'm not sure if it's normal.
> ---
>  net/bridge/br_netfilter_ipv6.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/net/bridge/br_netfilter_ipv6.c b/net/bridge/br_netfilter_ipv6.c
> index 6d12d26..7046e19 100644
> --- a/net/bridge/br_netfilter_ipv6.c
> +++ b/net/bridge/br_netfilter_ipv6.c
> @@ -140,11 +140,16 @@ int br_validate_ipv6(struct sk_buff *skb)
>  	/* No IP options in IPv6 header; however it should be
>  	 * checked if some next headers need special treatment
>  	 */
> +
> +	in6_dev_put(idev);
> +
>  	return 0;
>  
>  inhdr_error:
>  	IP6_INC_STATS_BH(dev_net(dev), idev, IPSTATS_MIB_INHDRERRORS);
>  drop:
> +	in6_dev_put(idev);
> +
>  	return -1;
>  }
>  
> 

Re: [PATCH] net/bridge: Add missing in6_dev_put in br_validate_ipv6

[Julien Grall]

Hi,

On 03/07/15 21:42, Florian Westphal wrote:
> Julien Grall <julien.grall@citrix.com> wrote:
>> The commit efb6de9b4ba0092b2c55f6a52d16294a8a698edd "netfilter: bridge:
>> forward IPv6 fragmented packets" introduced a new function
>> br_validate_ipv6 which take a reference on the inet6 device. Although,
>> the reference is not released at the end.
>>
>> This will result to the impossibility to destroy any netdevice using
>> ipv6 and bridge.
>>
>> Spotted while trying to destroy a Xen guest on the upstream Linux:
>> "unregister_netdevice: waiting for vif1.0 to become free. Usage count = 1"
> 
> Ugh :-/
> 
> I think it makes more sense to use __in6_dev_get() instead which doesn't
> take a reference.

__in6_dev_get requires to hold rcu_read_lock or RTNL. My knowledge on
this code is very limited. Are we sure that one this lock is hold? At
first glance, I wasn't able to find one.

Regards,

-- 
Julien Grall

Re: [PATCH] net/bridge: Add missing in6_dev_put in br_validate_ipv6

[Eric Dumazet]

On Mon, 2015-07-06 at 11:35 +0100, Julien Grall wrote:

> __in6_dev_get requires to hold rcu_read_lock or RTNL. My knowledge on
> this code is very limited. Are we sure that one this lock is hold? At
> first glance, I wasn't able to find one.

You could play it safe ;)

diff --git a/net/bridge/br_netfilter_ipv6.c b/net/bridge/br_netfilter_ipv6.c
index 6d12d2675c80..90e8ccc21cc5 100644
--- a/net/bridge/br_netfilter_ipv6.c
+++ b/net/bridge/br_netfilter_ipv6.c
@@ -104,10 +104,12 @@ int br_validate_ipv6(struct sk_buff *skb)
 {
 	const struct ipv6hdr *hdr;
 	struct net_device *dev = skb->dev;
-	struct inet6_dev *idev = in6_dev_get(skb->dev);
+	struct inet6_dev *idev;
 	u32 pkt_len;
 	u8 ip6h_len = sizeof(struct ipv6hdr);
 
+	rcu_read_lock();
+	idev = __in6_dev_get(dev);
 	if (!pskb_may_pull(skb, ip6h_len))
 		goto inhdr_error;
 
@@ -140,11 +142,13 @@ int br_validate_ipv6(struct sk_buff *skb)
 	/* No IP options in IPv6 header; however it should be
 	 * checked if some next headers need special treatment
 	 */
+	rcu_read_unlock();
 	return 0;
 
 inhdr_error:
 	IP6_INC_STATS_BH(dev_net(dev), idev, IPSTATS_MIB_INHDRERRORS);
 drop:
+	rcu_read_unlock();
 	return -1;
 }
 

Re: [PATCH] net/bridge: Add missing in6_dev_put in br_validate_ipv6

[Florian Westphal]

Julien Grall <julien.grall@citrix.com> wrote:
> On 03/07/15 21:42, Florian Westphal wrote:
> > I think it makes more sense to use __in6_dev_get() instead which doesn't
> > take a reference.
> 
> __in6_dev_get requires to hold rcu_read_lock or RTNL. My knowledge on
> this code is very limited. Are we sure that one this lock is hold? At
> first glance, I wasn't able to find one.

All netfilter hooks are rcu_read_locked via nf_hook_slow().

BTW, netfilter patches should be sent to netfilter-devel@vger.kernel.org.

Re: [Xen-devel] [PATCH] net/bridge: Add missing in6_dev_put in br_validate_ipv6

[Julien Grall]

On 06/07/15 12:19, Florian Westphal wrote:
> Julien Grall <julien.grall@citrix.com> wrote:
>> On 03/07/15 21:42, Florian Westphal wrote:
>>> I think it makes more sense to use __in6_dev_get() instead which doesn't
>>> take a reference.
>>
>> __in6_dev_get requires to hold rcu_read_lock or RTNL. My knowledge on
>> this code is very limited. Are we sure that one this lock is hold? At
>> first glance, I wasn't able to find one.
> 
> All netfilter hooks are rcu_read_locked via nf_hook_slow().

Ok. I will resend the patch with __in6_dev_get.

> BTW, netfilter patches should be sent to netfilter-devel@vger.kernel.org.

I used scripts/get_maintainer.pl which doesn't provide this mailing list
for net/bridge/br_netfilter*.c

Regards,

-- 
Julien Grall