[PATCH net v2 0/2] bridge/vxlan: fix reading neigh ha without synchronization

[Nikolay Aleksandrov <razor@blackwall.org>]

Hi,
Neigh ha address must be read using the seqlock to get a stable snapshot.
Both the bridge and vxlan read it directly and can see partial updates.
I reproduced both issues with running neigh updates and exercising these
paths in parallel and saw partial addresses, e.g. updating between
neigh A: 02:00:00:00:00:00 neigh B: fe:ff:ff:ff:ff:ff was able to observe
02:00:ff:ff:ff:ff and fe:ff:00:00:00:00 in packets. Noticed this initially
in the bridge, then checked vxlan and its arp/neigh_reduce functions have
the same bug, route_shortcircuit is doing the right thing already.

v1 link: https://lore.kernel.org/netdev/20260817143613.685769-1-razor@blackwall.org/
v2: - use ETH_ALEN instead of MAX_ADDR_LEN, the bridge devices all use
      ETH_ALEN and vxlan allows arp/nd reduce only when not in raw/gpe
      so it also always uses ETH_ALEN
    - align ha to 2 bytes because ether_addr_copy() expects it (Sashiko)

2-byte alignment is not strictly necessary everywhere (e.g. the ARP
suppress side can't reach ether_addr_copy) but it doesn't cost us anything
and is aligned with the rest of the code.

Cheers,
 Nik

Nikolay Aleksandrov (2):
  net: bridge: arp/nd proxy: fix reading neigh ha
  vxlan: fix reading neigh ha

 drivers/net/vxlan/vxlan_core.c | 20 +++++++++++++-------
 net/bridge/br_arp_nd_proxy.c   | 24 ++++++++++++++----------
 2 files changed, 27 insertions(+), 17 deletions(-)

-- 
2.47.3