netdev - [PATCH net v2] net: bridge: fix early call to br_stp_change_bridge

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Date:   Mon, 18 Dec 2017 17:35:09 +0200
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     netdev@...r.kernel.org
Cc:     makita.toshiaki@....ntt.co.jp, roopa@...ulusnetworks.com,
        davem@...emloft.net, stephen@...workplumber.org, avagin@...il.com,
        bridge@...ts.linux-foundation.org, idosch@...lanox.com,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Subject: [PATCH net v2] net: bridge: fix early call to br_stp_change_bridge_id and plug newlink leaks

The early call to br_stp_change_bridge_id in bridge's newlink can cause
a memory leak if an error occurs during the newlink because the fdb
entries are not cleaned up if a different lladdr was specified, also
another minor issue is that it generates fdb notifications with
ifindex = 0. Another unrelated memory leak is the bridge sysfs entries
which get added on NETDEV_REGISTER event, but are not cleaned up in the
newlink error path. To remove this special case the call to
br_stp_change_bridge_id is done after netdev register and we cleanup the
bridge on changelink error via br_dev_delete to plug all leaks.

This patch makes netlink bridge destruction on newlink error the same as
dellink and ioctl del which is necessary since at that point we have a
fully initialized bridge device.

To reproduce the issue:
$ ip l add br0 address 00:11:22:33:44:55 type bridge group_fwd_mask 1
RTNETLINK answers: Invalid argument

$ rmmod bridge
[ 1822.142525] =============================================================================
[ 1822.143640] BUG bridge_fdb_cache (Tainted: G           O    ): Objects remaining in bridge_fdb_cache on __kmem_cache_shutdown()
[ 1822.144821] -----------------------------------------------------------------------------

[ 1822.145990] Disabling lock debugging due to kernel taint
[ 1822.146732] INFO: Slab 0x0000000092a844b2 objects=32 used=2 fp=0x00000000fef011b0 flags=0x1ffff8000000100
[ 1822.147700] CPU: 2 PID: 13584 Comm: rmmod Tainted: G    B      O     4.15.0-rc2+ #87
[ 1822.148578] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
[ 1822.150008] Call Trace:
[ 1822.150510]  dump_stack+0x78/0xa9
[ 1822.151156]  slab_err+0xb1/0xd3
[ 1822.151834]  ? __kmalloc+0x1bb/0x1ce
[ 1822.152546]  __kmem_cache_shutdown+0x151/0x28b
[ 1822.153395]  shutdown_cache+0x13/0x144
[ 1822.154126]  kmem_cache_destroy+0x1c0/0x1fb
[ 1822.154669]  SyS_delete_module+0x194/0x244
[ 1822.155199]  ? trace_hardirqs_on_thunk+0x1a/0x1c
[ 1822.155773]  entry_SYSCALL_64_fastpath+0x23/0x9a
[ 1822.156343] RIP: 0033:0x7f929bd38b17
[ 1822.156859] RSP: 002b:00007ffd160e9a98 EFLAGS: 00000202 ORIG_RAX: 00000000000000b0
[ 1822.157728] RAX: ffffffffffffffda RBX: 00005578316ba090 RCX: 00007f929bd38b17
[ 1822.158422] RDX: 00007f929bd9ec60 RSI: 0000000000000800 RDI: 00005578316ba0f0
[ 1822.159114] RBP: 0000000000000003 R08: 00007f929bff5f20 R09: 00007ffd160e8a11
[ 1822.159808] R10: 00007ffd160e9860 R11: 0000000000000202 R12: 00007ffd160e8a80
[ 1822.160513] R13: 0000000000000000 R14: 0000000000000000 R15: 00005578316ba090
[ 1822.161278] INFO: Object 0x000000007645de29 @offset=0
[ 1822.161666] INFO: Object 0x00000000d5df2ab5 @offset=128

Fixes: 30313a3d5794 ("bridge: Handle IFLA_ADDRESS correctly when creating bridge device")
Fixes: 5b8d5429daa0 ("bridge: netlink: register netdevice before executing changelink")
Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
---
v2: it's better to use br_dev_delete to clean up because the sysfs entries
were leaked as well, basically we use it for the bridge fdb flush and sysfs
entries delete

Consequently this also would fix the null ptr deref due to the rhashtable
not being initialized in net-next when br_stp_change_bridge_id is called.

 net/bridge/br_netlink.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index d0ef0a8e8831..015f465c514b 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -1262,19 +1262,20 @@ static int br_dev_newlink(struct net *src_net, struct net_device *dev,
 	struct net_bridge *br = netdev_priv(dev);
 	int err;
 
+	err = register_netdevice(dev);
+	if (err)
+		return err;
+
 	if (tb[IFLA_ADDRESS]) {
 		spin_lock_bh(&br->lock);
 		br_stp_change_bridge_id(br, nla_data(tb[IFLA_ADDRESS]));
 		spin_unlock_bh(&br->lock);
 	}
 
-	err = register_netdevice(dev);
-	if (err)
-		return err;
-
 	err = br_changelink(dev, tb, data, extack);
 	if (err)
-		unregister_netdevice(dev);
+		br_dev_delete(dev, NULL);
+
 	return err;
 }
 
-- 
2.14.3