[BUG] Crash in network_info_get_roam_frequencies() when a neighbor report completes with -ENOTCONN during disconnect teardown

[BUG] Crash in network_info_get_roam_frequencies() when a neighbor report completes with -ENOTCONN during disconnect teardown

[Muhammed Izzet Saglam]

Hi,

iwd 3.12 crashes with SIGSEGV while roaming, when a pending 802.11k
neighbor report request completes during connection teardown. The
neighbor report callback only bails out on -ENODEV, so an -ENOTCONN
completion falls through to a roam scan that dereferences the connection
state netdev_connect_free() has just torn down.

I hit this twice within one minute on 2026-07-25 and captured both core
dumps. The backtraces are identical, so this looks deterministic rather
than memory corruption.

Backtrace (both dumps, identical):

  #0  network_info_get_roam_frequencies (info=0x0, current_freq=2462,
          max=max@entry=5 '\005') at src/knownnetworks.c:391
  #1  station_roam_scan_known_freqs (station=station@entry=0x564903a82b50)
          at src/station.c:3088
  #2  station_neighbor_report_cb (netdev=<optimized out>, err=-107,
          reports=<optimized out>, reports_len=0,
          user_data=0x564903a82b50) at src/station.c:3129
  #3  netdev_connect_free (netdev=netdev@entry=0x564903a77c40)
          at src/netdev.c:867
  #4  netdev_connect_failed (netdev=0x564903a77c40, result=<optimized out>,
          status_or_reason=<optimized out>) at src/netdev.c:937
  #5  netdev_disconnected (netdev=0x564903a77c40, result=<optimized out>,
          event=NETDEV_EVENT_DISCONNECT_BY_SME,
          status_or_reason=<optimized out>) at src/netdev.c:1004
  #6  netdev_disconnect_by_sme_cb (msg=<optimized out>,
          user_data=0x564903a77c40) at src/netdev.c:1019
  #7  process_unicast (genl=<optimized out>, nlmsg=0x7ffffcf571d0)
          at ell/genl.c:860
  #8  received_data (io=<optimized out>, user_data=0x564903a69bb0)
          at ell/genl.c:972
  #9  io_callback (fd=<optimized out>, events=1, user_data=0x564903a69b00)
          at ell/io.c:105
  #10 l_main_iterate (timeout=<optimized out>) at ell/main.c:463
  #11 l_main_run () at ell/main.c:511
  #12 l_main_run () at ell/main.c:492
  #13 l_main_run_with_signal (callback=0x5648f3df5bc0 <signal_handler>,
          user_data=0x0) at ell/main.c:633
  #14 main (argc=<optimized out>, argv=<optimized out>) at src/main.c:610

The faulting line is knownnetworks.c:391, with info == NULL:

  for (entry = l_queue_get_entries(info->known_frequencies); entry && max;

Sequence, as I read it:

  1. The AP disconnects us, so netdev_disconnect_by_sme_cb() runs
     (NETDEV_EVENT_DISCONNECT_BY_SME).
  2. netdev_connect_failed() -> netdev_connect_free() tears the
     connection down and completes the outstanding neighbor report
     request with an error.
  3. station_neighbor_report_cb() is invoked with err = -107
     (-ENOTCONN).
  4. The guard at the top of that callback only returns early for
     -ENODEV:

        if (!station->preparing_roam || err == -ENODEV)
                return;

     so -ENOTCONN continues to:

        if (!reports || err) {
                r = station_roam_scan_known_freqs(station);

  5. station_roam_scan_known_freqs() then reaches
     network_info_get_roam_frequencies() with the network info already
     gone, and dereferences NULL.

Commit 155c266 ("station: add checks to prevent multiple roam scans",
Jan 2023) fixed a different path to the same crash signature and is of
course already in 3.12. This one arrives through the disconnect teardown
rather than the roam rearm timer, and the code in master still looks
affected: station_neighbor_report_cb() special-cases -ENODEV only, and
station_roam_scan_known_freqs() has no NULL check on the connected
network.

I have not written a patch because I do not know which fix you would
prefer -- treating any err as terminal in the callback, checking
station->connected_network before the fallback scan, or cancelling the
neighbor report request earlier in netdev_connect_free(). Happy to test
a patch on this hardware.

System:

  iwd            3.12 (Arch Linux, iwd 3.12-1)
  kernel         7.1.5-zen1-1-zen (x86_64)
  device         Intel Wi-Fi 6E AX210/AX1675 2x2 [Typhoon Peak]
                 [8086:2725] rev 1a, iwlwifi
  firmware       89.735b75a4.0 ty-a0-gf-a0-89.ucode, op_mode iwlmvm
  band at crash  2462 MHz (2.4 GHz, channel 11), roaming on a weak link

Both core dumps are still on disk if anything else would help.

Thanks,
Muhammed Izzet Saglam