From b1b9d366028ff580e6dd80b48a69c473361456f1 Mon Sep 17 00:00:00 2001 From: Xin Long Date: Tue, 25 Apr 2017 22:58:37 +0800 Subject: [PATCH] bridge: move bridge multicast cleanup to ndo_uninit During removing a bridge device, if the bridge is still up, a new mdb entry still can be added in br_multicast_add_group() after all mdb entries are removed in br_multicast_dev_del(). Like the path: mld_ifc_timer_expire -> mld_sendpack -> ... br_multicast_rcv -> br_multicast_add_group The new mp's timer will be set up. If the timer expires after the bridge is freed, it may cause use-after-free panic in br_multicast_group_expired. BUG: unable to handle kernel NULL pointer dereference at 0000000000000048 IP: [] br_multicast_group_expired+0x28/0xb0 [bridge] Call Trace: [] call_timer_fn+0x36/0x110 [] ? br_mdb_free+0x30/0x30 [bridge] [] run_timer_softirq+0x237/0x340 [] __do_softirq+0xef/0x280 [] call_softirq+0x1c/0x30 [] do_softirq+0x65/0xa0 [] irq_exit+0x115/0x120 [] smp_apic_timer_interrupt+0x45/0x60 [] apic_timer_interrupt+0x6d/0x80 Nikolay also found it would cause a memory leak - the mdb hash is reallocated and not freed due to the mdb rehash. unreferenced object 0xffff8800540ba800 (size 2048): backtrace: [] kmemleak_alloc+0x67/0xc0 [] __kmalloc+0x1ba/0x3e0 [] br_mdb_rehash+0x5e/0x340 [bridge] [] br_multicast_new_group+0x43f/0x6e0 [bridge] [] br_multicast_add_group+0x203/0x260 [bridge] [] br_multicast_rcv+0x945/0x11d0 [bridge] [] br_dev_xmit+0x180/0x470 [bridge] [] dev_hard_start_xmit+0xbb/0x3d0 [] __dev_queue_xmit+0xb13/0xc10 [] dev_queue_xmit+0x10/0x20 [] ip6_finish_output2+0x5ca/0xac0 [ipv6] [] ip6_finish_output+0x126/0x2c0 [ipv6] [] ip6_output+0xe5/0x390 [ipv6] [] NF_HOOK.constprop.44+0x6c/0x240 [ipv6] [] mld_sendpack+0x216/0x3e0 [ipv6] [] mld_ifc_timer_expire+0x18b/0x2b0 [ipv6] This could happen when ip link remove a bridge or destroy a netns with a bridge device inside. With Nikolay's suggestion, this patch is to clean up bridge multicast in ndo_uninit after bridge dev is shutdown, instead of br_dev_delete, so that netif_running check in br_multicast_add_group can avoid this issue. v1->v2: - fix this issue by moving br_multicast_dev_del to ndo_uninit, instead of calling dev_close in br_dev_delete. (NOTE: Depends upon b6fe0440c637 ("bridge: implement missing ndo_uninit()")) Fixes: e10177abf842 ("bridge: multicast: fix handling of temp and perm entries") Reported-by: Jianwen Ji Signed-off-by: Xin Long Reviewed-by: Stephen Hemminger Signed-off-by: Nikolay Aleksandrov Signed-off-by: David S. Miller --- net/bridge/br_device.c | 1 + net/bridge/br_if.c | 1 - 2 files changed, 1 insertion(+), 1 deletion(-) diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c index 90f49a194249..430b53e7d941 100644 --- a/net/bridge/br_device.c +++ b/net/bridge/br_device.c @@ -123,6 +123,7 @@ static void br_dev_uninit(struct net_device *dev) { struct net_bridge *br = netdev_priv(dev); + br_multicast_dev_del(br); br_multicast_uninit_stats(br); br_vlan_flush(br); free_percpu(br->stats); diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c index 56a2a72e7738..a8d0ed282a10 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_multicast_dev_del(br); cancel_delayed_work_sync(&br->gc_work); br_sysfs_delbr(br->dev); -- 2.30.2