[BUG] WARNING in lowpan_compress_addr_64

[Farhad Alemi]

Hello,

As part of the kernel research at ASU's SEFCOM
lab, we hit the crash below. Crash reports can be found here:

  https://github.com/farhad-alemi/public_bug_reports/tree/main/182-warning-in-lowpan-compress-addr-64/

  WARNING: net/6lowpan/iphc.c:937 at
lowpan_iphc_compress_802154_lladdr net/6lowpan/iphc.c:937 [inline],
CPU#0: syz.9.76/13660
  WARNING: net/6lowpan/iphc.c:937 at
lowpan_compress_addr_64+0x4be/0x9c0 net/6lowpan/iphc.c:952, CPU#0:
syz.9.76/13660
  RIP: 0010:lowpan_compress_addr_64+0x4be/0x9c0 net/6lowpan/iphc.c:952
  Call Trace:
   lowpan_compress_addr_64+0x4be/0x9c0 net/6lowpan/iphc.c:952
   lowpan_header_compress+0xeef/0x1ef0 net/6lowpan/iphc.c:1242
   lowpan_header net/ieee802154/6lowpan/tx.c:234 [inline]
   lowpan_xmit+0x4c6/0x1420 net/ieee802154/6lowpan/tx.c:282
   dev_hard_start_xmit+0x23b/0x620 net/core/dev.c:3904
   __dev_queue_xmit+0x11e7/0x3250 net/core/dev.c:4870
   packet_snd net/packet/af_packet.c:3082 [inline]
   packet_sendmsg+0x3d9b/0x5150 net/packet/af_packet.c:3114
  Kernel panic - not syncing: kernel: panic_on_warn set ...

Our reproducer.c is available upon request.

Happy to test a patch if that would help.

Regards,