Re: [PATCH net v2] veth: manage XDP program pointers during channel resize

On 09/21, Jakub Kicinski wrote:

veth_set_channels() tears down XDP resources for removed RX queues
without clearing rq->xdp_prog.  If the program is then detached or
replaced, those queues keep the old pointer after bpf_prog_put().
A later channel increase can re-enable NAPI and run the freed program.

  BUG: unable to handle page fault for address: ffffc90000256048
  Oops: Oops: 0000 [#1] SMP KASAN NOPTI
  RIP: veth_xdp_rcv_skb (include/linux/filter.h:779
                         include/net/xdp.h:696 drivers/net/veth.c:820)
  Call Trace:
   veth_xdp_rcv (drivers/net/veth.c:941)
   veth_poll (drivers/net/veth.c:986)
   __napi_poll (net/core/dev.c:7787)
   net_rx_action (net/core/dev.c:7850 net/core/dev.c:8007)
   handle_softirqs (kernel/softirq.c:645)
  Kernel panic - not syncing: Fatal exception in interrupt

Fixes: 4752eeb3d891 ("veth: implement support for set_channel ethtool op")
Signed-off-by: Weiming Shi <redacted>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Acked-by: Stanislav Fomichev <sdf@fomichev.me>