path: root/net
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authorNikolay Aleksandrov <nikolay@cumulusnetworks.com>2019-12-03 16:48:06 +0200
committerDavid S. Miller <davem@davemloft.net>2019-12-03 11:21:20 -0800
commitc4b4c421857dc7b1cf0dccbd738472360ff2cd70 (patch)
tree0b19889e2d829255793e43e6e725eddb9847441a /net
parentnet: fix a leak in register_netdevice() (diff)
net: bridge: deny dev_set_mac_address() when unregistering
We have an interesting memory leak in the bridge when it is being unregistered and is a slave to a master device which would change the mac of its slaves on unregister (e.g. bond, team). This is a very unusual setup but we do end up leaking 1 fdb entry because dev_set_mac_address() would cause the bridge to insert the new mac address into its table after all fdbs are flushed, i.e. after dellink() on the bridge has finished and we call NETDEV_UNREGISTER the bond/team would release it and will call dev_set_mac_address() to restore its original address and that in turn will add an fdb in the bridge. One fix is to check for the bridge dev's reg_state in its ndo_set_mac_address callback and return an error if the bridge is not in NETREG_REGISTERED. Easy steps to reproduce: 1. add bond in mode != A/B 2. add any slave to the bond 3. add bridge dev as a slave to the bond 4. destroy the bridge device Trace: unreferenced object 0xffff888035c4d080 (size 128): comm "ip", pid 4068, jiffies 4296209429 (age 1413.753s) hex dump (first 32 bytes): 41 1d c9 36 80 88 ff ff 00 00 00 00 00 00 00 00 A..6............ d2 19 c9 5e 3f d7 00 00 00 00 00 00 00 00 00 00 ...^?........... backtrace: [<00000000ddb525dc>] kmem_cache_alloc+0x155/0x26f [<00000000633ff1e0>] fdb_create+0x21/0x486 [bridge] [<0000000092b17e9c>] fdb_insert+0x91/0xdc [bridge] [<00000000f2a0f0ff>] br_fdb_change_mac_address+0xb3/0x175 [bridge] [<000000001de02dbd>] br_stp_change_bridge_id+0xf/0xff [bridge] [<00000000ac0e32b1>] br_set_mac_address+0x76/0x99 [bridge] [<000000006846a77f>] dev_set_mac_address+0x63/0x9b [<00000000d30738fc>] __bond_release_one+0x3f6/0x455 [bonding] [<00000000fc7ec01d>] bond_netdev_event+0x2f2/0x400 [bonding] [<00000000305d7795>] notifier_call_chain+0x38/0x56 [<0000000028885d4a>] call_netdevice_notifiers+0x1e/0x23 [<000000008279477b>] rollback_registered_many+0x353/0x6a4 [<0000000018ef753a>] unregister_netdevice_many+0x17/0x6f [<00000000ba854b7a>] rtnl_delete_link+0x3c/0x43 [<00000000adf8618d>] rtnl_dellink+0x1dc/0x20a [<000000009b6395fd>] rtnetlink_rcv_msg+0x23d/0x268 Fixes: 43598813386f ("bridge: add local MAC address to forwarding table (v2)") Reported-by: syzbot+2add91c08eb181fea1bf@syzkaller.appspotmail.com Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
1 files changed, 6 insertions, 0 deletions
diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index 434effde02c3..fb38add21b37 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -245,6 +245,12 @@ static int br_set_mac_address(struct net_device *dev, void *p)
if (!is_valid_ether_addr(addr->sa_data))
+ /* dev_set_mac_addr() can be called by a master device on bridge's
+ * NETDEV_UNREGISTER, but since it's being destroyed do nothing
+ */
+ if (dev->reg_state != NETREG_REGISTERED)
+ return -EBUSY;
if (!ether_addr_equal(dev->dev_addr, addr->sa_data)) {
/* Mac address will be changed in br_stp_change_bridge_id(). */