From a5b8fd657881003ea11c193d147c8f4ba143725d Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Wed, 29 Sep 2021 08:32:24 -0700 Subject: net: dev_addr_list: handle first address in __hw_addr_add_ex struct dev_addr_list is used for device addresses, unicast addresses and multicast addresses. The first of those needs special handling of the main address - netdev->dev_addr points directly the data of the entry and drivers write to it freely, so we can't maintain it in the rbtree (for now, at least, to be fixed in net-next). Current work around sprinkles special handling of the first address on the list throughout the code but it missed the case where address is being added. First address will not be visible during subsequent adds. Syzbot found a warning where unicast addresses are modified without holding the rtnl lock, tl;dr is that team generates the same modification multiple times, not necessarily when right locks are held. In the repro we have: macvlan -> team -> veth macvlan adds a unicast address to the team. Team then pushes that address down to its memebers (veths). Next something unrelated makes team sync member addrs again, and because of the bug the addr entries get duplicated in the veths. macvlan gets removed, removes its addr from team which removes only one of the duplicated addresses from veths. This removal is done under rtnl. Next syzbot uses iptables to add a multicast addr to team (which does not hold rtnl lock). Team syncs veth addrs, but because veths' unicast list still has the duplicate it will also get sync, even though this update is intended for mc addresses. Again, uc address updates need rtnl lock, boom. Reported-by: syzbot+7a2ab2cdc14d134de553@syzkaller.appspotmail.com Fixes: 406f42fa0d3c ("net-next: When a bond have a massive amount of VLANs with IPv6 addresses, performance of changing link state, attaching a VRF, changing an IPv6 address, etc. go down dramtically.") Signed-off-by: Jakub Kicinski Signed-off-by: David S. Miller --- net/core/dev_addr_lists.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'net') diff --git a/net/core/dev_addr_lists.c b/net/core/dev_addr_lists.c index 8c39283c26ae..f0cb38344126 100644 --- a/net/core/dev_addr_lists.c +++ b/net/core/dev_addr_lists.c @@ -50,6 +50,11 @@ static int __hw_addr_add_ex(struct netdev_hw_addr_list *list, if (addr_len > MAX_ADDR_LEN) return -EINVAL; + ha = list_first_entry(&list->list, struct netdev_hw_addr, list); + if (ha && !memcmp(addr, ha->addr, addr_len) && + (!addr_type || addr_type == ha->type)) + goto found_it; + while (*ins_point) { int diff; @@ -64,6 +69,7 @@ static int __hw_addr_add_ex(struct netdev_hw_addr_list *list, } else if (diff > 0) { ins_point = &parent->rb_right; } else { +found_it: if (exclusive) return -EEXIST; if (global) { -- cgit v1.2.3-70-g09d2