RDMA/core: Fix stale RoCE GIDs during netdev events at registration

RDMA/core: Fix stale RoCE GIDs during netdev events at registration

RoCE GID entries become stale when netdev properties change during the
IB device registration window. This is reproducible with a udev rule
that sets a MAC address when a VF netdev appears:

  ACTION=="add", SUBSYSTEM=="net", KERNEL=="eth4", \
    RUN+="/sbin/ip link set eth4 address 88:22:33:44:55:66"

After VF creation, show_gids displays GIDs derived from the original
random MAC rather than the configured one.

The root cause is a race between netdev event processing and device
registration:

  CPU 0 (driver)                    CPU 1 (udev/workqueue)
  ──────────────                    ──────────────────────
  ib_register_device()
    ib_cache_setup_one()
      gid_table_setup_one()
        _gid_table_setup_one()
          ← GID table allocated
        rdma_roce_rescan_device()
          ← GIDs populated with
            OLD MAC
                                    ip link set eth4 addr NEW_MAC
                                    NETDEV_CHANGEADDR queued
                                    netdevice_event_work_handler()
                                      ib_enum_all_roce_netdevs()
                                        ← Iterates DEVICE_REGISTERED
                                        ← Device NOT marked yet, SKIP!
    enable_device_and_get()
      xa_set_mark(DEVICE_REGISTERED)
          ← Too late, event was lost

The netdev event handler uses ib_enum_all_roce_netdevs() which only
iterates devices marked DEVICE_REGISTERED. However, this mark is set
late in the registration process, after the GID cache is already
populated. Events arriving in this window are silently dropped.

Fix this by introducing a new xarray mark DEVICE_GID_UPDATES that is
set immediately after the GID table is allocated and initialized. Use
the new mark in ib_enum_all_roce_netdevs() function to iterate devices
instead of DEVICE_REGISTERED.

This is safe because:
- After _gid_table_setup_one(), all required structures exist (port_data,
  immutable, cache.gid)
- The GID table mutex serializes concurrent access between the initial
  rescan and event handlers
- Event handlers correctly update stale GIDs even when racing with rescan
- The mark is cleared in ib_cache_cleanup_one() before teardown

This also fixes similar races for IP address events (inetaddr_event,
inet6addr_event) which use the same enumeration path.

Fixes: 0df91bb67334 ("RDMA/devices: Use xarray to store the client_data")
Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Link: https://patch.msgid.link/20260127093839.126291-1-jiri@resnulli.us
Reported-by: syzbot+881d65229ca4f9ae8c84@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=881d65229ca4f9ae8c84
Signed-off-by: Leon Romanovsky <leon@kernel.org>