macsec: set IFF_UNICAST_FLT priv flag

Cosmin reports the following locking issue:

  # BUG: sleeping function called from invalid context at
  kernel/locking/mutex.c:275
  #   dump_stack_lvl+0x4f/0x60
  #   __might_resched+0xeb/0x140
  #   mutex_lock+0x1a/0x40
  #   dev_set_promiscuity+0x26/0x90
  #   __dev_set_promiscuity+0x85/0x170
  #   __dev_set_rx_mode+0x69/0xa0
  #   dev_uc_add+0x6d/0x80
  #   vlan_dev_open+0x5f/0x120 [8021q]
  #  __dev_open+0x10c/0x2a0
  #  __dev_change_flags+0x1a4/0x210
  #  netif_change_flags+0x22/0x60
  #  do_setlink.isra.0+0xdb0/0x10f0
  #  rtnl_newlink+0x797/0xb00
  #  rtnetlink_rcv_msg+0x1cb/0x3f0
  #  netlink_rcv_skb+0x53/0x100
  #  netlink_unicast+0x273/0x3b0
  #  netlink_sendmsg+0x1f2/0x430

Which is similar to recent syzkaller reports in [0] and [1] and triggers
because macsec does not advertise IFF_UNICAST_FLT although it has proper
ndo_set_rx_mode callback that takes care of pushing uc/mc addresses
down to the real device.

In general, dev_uc_add call path is problematic for stacking
non-IFF_UNICAST_FLT because we might grab netdev instance lock under
addr_list_lock spinlock, so this is not a systemic fix.

0: https://lore.kernel.org/netdev/686d55b4.050a0220.1ffab7.0014.GAE@google.com
1: https://lore.kernel.org/netdev/68712acf.a00a0220.26a83e.0051.GAE@google.com/
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/netdev/2aff4342b0f5b1539c02ffd8df4c7e58dd9746e7.camel@nvidia.com
Fixes: 7e4d784f5810 ("net: hold netdev instance lock during rtnetlink operations")
Reported-by: Cosmin Ratiu <cratiu@nvidia.com>
Tested-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250723224715.1341121-1-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions