Linux Ethernet Bridging - Jul 2015 - [Bridge] [PATCH] net/bridge: Add missing in6_dev_put in br_validate_ipv6

Julien Grall <julien.grall at 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.

Hi,

On 03/07/15 21:42, Florian Westphal wrote:
> Julien Grall <julien.grall at 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