Linux Ethernet Bridging - Apr 2017 - [Bridge] [PATCH net v3 0/2] bridge: Fix kernel oops during bridge creation

From: Ido Schimmel <idosch at mellanox.com>

First patch adds a missing ndo_uninit() in the bridge driver, which is a
prerequisite for the second patch that actually fixes the oops.

Please consider both patches for 4.4.y, 4.9.y and 4.10.y

Ido Schimmel (2):
  bridge: implement missing ndo_uninit()
  bridge: netlink: register netdevice before executing changelink

 net/bridge/br_device.c    | 20 +++++++++++---------
 net/bridge/br_if.c        |  1 -
 net/bridge/br_multicast.c |  7 +++++--
 net/bridge/br_netlink.c   |  7 +++++--
 net/bridge/br_private.h   |  5 +++++
 5 files changed, 26 insertions(+), 14 deletions(-)

-- 
2.9.3

From: Ido Schimmel <idosch at mellanox.com>

While the bridge driver implements an ndo_init(), it was missing a
symmetric ndo_uninit(), causing the different de-initialization
operations to be scattered around its dellink() and destructor().

Implement a symmetric ndo_uninit() and remove the overlapping operations
from its dellink() and destructor().

This is a prerequisite for the next patch, as it allows us to have a
proper cleanup upon changelink() failure during the bridge's newlink().

Fixes: b6677449dff6 ("bridge: netlink: call br_changelink() during
br_dev_newlink()")
Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
Signed-off-by: Ido Schimmel <idosch at mellanox.com>
---
v2->v3:
* Use free_netdev() for destructor()
v1->v2:
* New patch

 net/bridge/br_device.c    | 20 +++++++++++---------
 net/bridge/br_if.c        |  1 -
 net/bridge/br_multicast.c |  7 +++++--
 net/bridge/br_private.h   |  5 +++++
 4 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index ea71513..90f49a1 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -119,6 +119,15 @@ static int br_dev_init(struct net_device *dev)
 	return err;
 }
 
+static void br_dev_uninit(struct net_device *dev)
+{
+	struct net_bridge *br = netdev_priv(dev);
+
+	br_multicast_uninit_stats(br);
+	br_vlan_flush(br);
+	free_percpu(br->stats);
+}
+
 static int br_dev_open(struct net_device *dev)
 {
 	struct net_bridge *br = netdev_priv(dev);
@@ -332,6 +341,7 @@ static const struct net_device_ops br_netdev_ops = {
 	.ndo_open		 = br_dev_open,
 	.ndo_stop		 = br_dev_stop,
 	.ndo_init		 = br_dev_init,
+	.ndo_uninit		 = br_dev_uninit,
 	.ndo_start_xmit		 = br_dev_xmit,
 	.ndo_get_stats64	 = br_get_stats64,
 	.ndo_set_mac_address	 = br_set_mac_address,
@@ -356,14 +366,6 @@ static const struct net_device_ops br_netdev_ops = {
 	.ndo_features_check	 = passthru_features_check,
 };
 
-static void br_dev_free(struct net_device *dev)
-{
-	struct net_bridge *br = netdev_priv(dev);
-
-	free_percpu(br->stats);
-	free_netdev(dev);
-}
-
 static struct device_type br_type = {
 	.name	= "bridge",
 };
@@ -376,7 +378,7 @@ void br_dev_setup(struct net_device *dev)
 	ether_setup(dev);
 
 	dev->netdev_ops = &br_netdev_ops;
-	dev->destructor = br_dev_free;
+	dev->destructor = free_netdev;
 	dev->ethtool_ops = &br_ethtool_ops;
 	SET_NETDEV_DEVTYPE(dev, &br_type);
 	dev->priv_flags = IFF_EBRIDGE | IFF_NO_QUEUE;
diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index 8ac1770..56a2a72 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -311,7 +311,6 @@ void br_dev_delete(struct net_device *dev, struct list_head
*head)
 
 	br_fdb_delete_by_port(br, NULL, 0, 1);
 
-	br_vlan_flush(br);
 	br_multicast_dev_del(br);
 	cancel_delayed_work_sync(&br->gc_work);
 
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index b760f26..faa7261 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -2031,8 +2031,6 @@ void br_multicast_dev_del(struct net_bridge *br)
 
 out:
 	spin_unlock_bh(&br->multicast_lock);
-
-	free_percpu(br->mcast_stats);
 }
 
 int br_multicast_set_router(struct net_bridge *br, unsigned long val)
@@ -2531,6 +2529,11 @@ int br_multicast_init_stats(struct net_bridge *br)
 	return 0;
 }
 
+void br_multicast_uninit_stats(struct net_bridge *br)
+{
+	free_percpu(br->mcast_stats);
+}
+
 static void mcast_stats_add_dir(u64 *dst, u64 *src)
 {
 	dst[BR_MCAST_DIR_RX] += src[BR_MCAST_DIR_RX];
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 6136818..0d17728 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -620,6 +620,7 @@ void br_rtr_notify(struct net_device *dev, struct
net_bridge_port *port,
 void br_multicast_count(struct net_bridge *br, const struct net_bridge_port *p,
 			const struct sk_buff *skb, u8 type, u8 dir);
 int br_multicast_init_stats(struct net_bridge *br);
+void br_multicast_uninit_stats(struct net_bridge *br);
 void br_multicast_get_stats(const struct net_bridge *br,
 			    const struct net_bridge_port *p,
 			    struct br_mcast_stats *dest);
@@ -760,6 +761,10 @@ static inline int br_multicast_init_stats(struct net_bridge
*br)
 	return 0;
 }
 
+static inline void br_multicast_uninit_stats(struct net_bridge *br)
+{
+}
+
 static inline int br_multicast_igmp_type(const struct sk_buff *skb)
 {
 	return 0;
-- 
2.9.3

From: Ido Schimmel <idosch at mellanox.com>

Peter reported a kernel oops when executing the following command:

$ ip link add name test type bridge vlan_default_pvid 1

[13634.939408] BUG: unable to handle kernel NULL pointer dereference at
0000000000000190
[13634.939436] IP: __vlan_add+0x73/0x5f0
[...]
[13634.939783] Call Trace:
[13634.939791]  ? pcpu_next_unpop+0x3b/0x50
[13634.939801]  ? pcpu_alloc+0x3d2/0x680
[13634.939810]  ? br_vlan_add+0x135/0x1b0
[13634.939820]  ? __br_vlan_set_default_pvid.part.28+0x204/0x2b0
[13634.939834]  ? br_changelink+0x120/0x4e0
[13634.939844]  ? br_dev_newlink+0x50/0x70
[13634.939854]  ? rtnl_newlink+0x5f5/0x8a0
[13634.939864]  ? rtnl_newlink+0x176/0x8a0
[13634.939874]  ? mem_cgroup_commit_charge+0x7c/0x4e0
[13634.939886]  ? rtnetlink_rcv_msg+0xe1/0x220
[13634.939896]  ? lookup_fast+0x52/0x370
[13634.939905]  ? rtnl_newlink+0x8a0/0x8a0
[13634.939915]  ? netlink_rcv_skb+0xa1/0xc0
[13634.939925]  ? rtnetlink_rcv+0x24/0x30
[13634.939934]  ? netlink_unicast+0x177/0x220
[13634.939944]  ? netlink_sendmsg+0x2fe/0x3b0
[13634.939954]  ? _copy_from_user+0x39/0x40
[13634.939964]  ? sock_sendmsg+0x30/0x40
[13634.940159]  ? ___sys_sendmsg+0x29d/0x2b0
[13634.940326]  ? __alloc_pages_nodemask+0xdf/0x230
[13634.940478]  ? mem_cgroup_commit_charge+0x7c/0x4e0
[13634.940592]  ? mem_cgroup_try_charge+0x76/0x1a0
[13634.940701]  ? __handle_mm_fault+0xdb9/0x10b0
[13634.940809]  ? __sys_sendmsg+0x51/0x90
[13634.940917]  ? entry_SYSCALL_64_fastpath+0x1e/0xad

The problem is that the bridge's VLAN group is created after setting the
default PVID, when registering the netdevice and executing its
ndo_init().

Fix this by changing the order of both operations, so that
br_changelink() is only processed after the netdevice is registered,
when the VLAN group is already initialized.

Fixes: b6677449dff6 ("bridge: netlink: call br_changelink() during
br_dev_newlink()")
Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
Signed-off-by: Ido Schimmel <idosch at mellanox.com>
Reported-by: Peter V. Saveliev <peter at svinota.eu>
Tested-by: Peter V. Saveliev <peter at svinota.eu>
---
v2->v3:
* Drop goto
v1->v2:
* Error-out on changelink() failure

 net/bridge/br_netlink.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index a8f6acd..225ef7d 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -1165,11 +1165,14 @@ static int br_dev_newlink(struct net *src_net, struct
net_device *dev,
 		spin_unlock_bh(&br->lock);
 	}
 
-	err = br_changelink(dev, tb, data);
+	err = register_netdevice(dev);
 	if (err)
 		return err;
 
-	return register_netdevice(dev);
+	err = br_changelink(dev, tb, data);
+	if (err)
+		unregister_netdevice(dev);
+	return err;
 }
 
 static size_t br_get_size(const struct net_device *brdev)
-- 
2.9.3

On Mon, 10 Apr 2017 14:59:26 +0300
idosch at idosch.org wrote:
> From: Ido Schimmel <idosch at mellanox.com>
> 
> First patch adds a missing ndo_uninit() in the bridge driver, which is a
> prerequisite for the second patch that actually fixes the oops.
> 
> Please consider both patches for 4.4.y, 4.9.y and 4.10.y
> 
> Ido Schimmel (2):
>   bridge: implement missing ndo_uninit()
>   bridge: netlink: register netdevice before executing changelink
> 
>  net/bridge/br_device.c    | 20 +++++++++++---------
>  net/bridge/br_if.c        |  1 -
>  net/bridge/br_multicast.c |  7 +++++--
>  net/bridge/br_netlink.c   |  7 +++++--
>  net/bridge/br_private.h   |  5 +++++
>  5 files changed, 26 insertions(+), 14 deletions(-)
> 
Looks good, thanks for following through on this.

Reviewed-by: Stephen Hemminger <stephen at networkplumber.org>

From: idosch at idosch.org
Date: Mon, 10 Apr 2017 14:59:26 +0300
> From: Ido Schimmel <idosch at mellanox.com>
> 
> First patch adds a missing ndo_uninit() in the bridge driver, which is a
> prerequisite for the second patch that actually fixes the oops.
> 
> Please consider both patches for 4.4.y, 4.9.y and 4.10.y
Series applied and queued up for -stable, thank you.