Re: [PATCH v2 net-next 1/3] bonding: fix bond_3ad_set_carrier() RCU usage

[Ding Tianhong <dingtianhong@huawei.com>]

On 2014/1/9 19:20, Veaceslav Falico wrote:
> Currently, its usage is just plainly wrong. It first gets a slave under
> RCU, and, after releasing the RCU lock, continues to use it - whilst it can
> be freed.
> 
> Fix this by ensuring that bond_3ad_set_carrier() is either under RCU read
> lock or under the RTNL lock (bond_set_carrier() always holds it).
> 
> Fixes: be79bd048ab ("bonding: add RCU for bond_3ad_state_machine_handler()")
> CC: dingtianhong@huawei.com
> CC: Jay Vosburgh <fubar@us.ibm.com>
> CC: Andy Gospodarek <andy@greyhouse.net>
> Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
> ---
> 
> Notes:
>     v1 -> v2:
>     Don't use _rcu primitives as we can be called under RTNL too.
> 
>  drivers/net/bonding/bond_3ad.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
> index 29db1ca..cf5fab8 100644
> --- a/drivers/net/bonding/bond_3ad.c
> +++ b/drivers/net/bonding/bond_3ad.c
> @@ -1597,9 +1597,9 @@ static void ad_agg_selection_logic(struct aggregator *agg)
>  		}
>  	}
>  
> -	rcu_read_unlock();
> -
>  	bond_3ad_set_carrier(bond);
> +
> +	rcu_read_unlock();
>  }
>  
>  /**
> @@ -2322,15 +2322,14 @@ void bond_3ad_handle_link_change(struct slave *slave, char link)
>   *
>   * Called by bond_set_carrier(). Return zero if carrier state does not
>   * change, nonzero if it does.
> + * The caller must hold RCU read lock or RTNL.
>   */
>  int bond_3ad_set_carrier(struct bonding *bond)
>  {
>  	struct aggregator *active;
>  	struct slave *first_slave;
>  
> -	rcu_read_lock();
> -	first_slave = bond_first_slave_rcu(bond);
> -	rcu_read_unlock();
> +	first_slave = bond_first_slave(bond);
>  	if (!first_slave)
>  		return 0;
>  	active = __get_active_agg(&(SLAVE_AD_INFO(first_slave).aggregator));
> 

Agree, thanks.

Acked-by: Ding Tianhong <dingtianhong@huawei.com>