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Date: Tue, 03 Mar 2015 06:31:29 -0800
From: roopa <roopa@...ulusnetworks.com>
To: Johannes Berg <johannes@...solutions.net>
CC: netdev@...r.kernel.org,
Stephen Hemminger <stephen@...workplumber.org>,
Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH v3] bridge: fix bridge netlink RCU usage
On 3/3/15, 5:49 AM, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@...el.com>
>
> When the STP timer fires, it can call br_ifinfo_notify(),
> which in turn ends up in the new br_get_link_af_size().
> This function is annotated to be using RTNL locking, which
> clearly isn't the case here, and thus lockdep warns:
>
> ===============================
> [ INFO: suspicious RCU usage. ]
> 3.19.0+ #569 Not tainted
> -------------------------------
> net/bridge/br_private.h:204 suspicious rcu_dereference_protected() usage!
>
> Fix this by doing RCU locking here.
>
> Fixes: b7853d73e39b ("bridge: add vlan info to bridge setlink and dellink notification messages")
> Signed-off-by: Johannes Berg <johannes.berg@...el.com>
> ---
> net/bridge/br_netlink.c | 15 ++++++++-------
> 1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
> index 17e0177467f5..72d8efa9b1eb 100644
> --- a/net/bridge/br_netlink.c
> +++ b/net/bridge/br_netlink.c
> @@ -25,19 +25,20 @@
> static size_t br_get_link_af_size(const struct net_device *dev)
> {
> struct net_port_vlans *pv;
> + unsigned int num_vlans;
>
> + rcu_read_lock();
> if (br_port_exists(dev))
> - pv = nbp_get_vlan_info(br_port_get_rtnl(dev));
> + pv = nbp_get_vlan_info(br_port_get_rcu(dev));
> else if (dev->priv_flags & IFF_EBRIDGE)
> - pv = br_get_vlan_info((struct net_bridge *)netdev_priv(dev));
> + pv = br_get_vlan_info(netdev_priv(dev));
> else
> - return 0;
> -
> - if (!pv)
> - return 0;
> + pv = NULL;
> + num_vlans = pv ? pv->num_vlans : 0;
> + rcu_read_unlock();
>
> /* Each VLAN is returned in bridge_vlan_info along with flags */
> - return pv->num_vlans * nla_total_size(sizeof(struct bridge_vlan_info));
> + return num_vlans * nla_total_size(sizeof(struct bridge_vlan_info));
> }
>
> static inline size_t br_port_info_size(void)
Thanks!
I used an existing function and did not realize I was newly adding the
stp notify case to the mix.
Will make sure I run with lockdep on next time.
My subsequent patch in net-next related to this code, changes things a
bit (fed0a159c8c5e453d79d6a73897c576efea0a8a5 bridge: fix link
notification skb size calculation to include vlan ranges).
It reverts the use of this function which makes sure this is always
called under rtnl.
But, I did add another version of this function in net-next which has
the same problem.
Assuming that patch in net-next is on its way to net soon, am wondering
if fixing it in net-next is the right course.
I can apply your patch there and re-submit. Or if you prefer to
re-submit your patch on net-next that's great too.
please let me know.
Thanks,
Roopa
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