Re: [syzbot] [net?] unregister_netdevice: waiting for DEV to become free (9)

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
unregister_netdevice: waiting for DEV to become free

unregister_netdevice: waiting for syz_tun to become free. Usage count = 8
ref_tracker: netdev@00000000adbd14c8 has 1/7 users at
     __netdev_tracker_alloc include/linux/netdevice.h:4471 [inline]
     netdev_tracker_alloc include/linux/netdevice.h:4483 [inline]
     netdev_get_by_index+0x88/0xe0 net/core/dev.c:1027
     fib6_nh_init+0x258/0x14bc net/ipv6/route.c:3606
     ip6_route_info_create_nh+0x120/0x9a8 net/ipv6/route.c:3905
     ip6_route_add+0x8c/0x1b4 net/ipv6/route.c:3957
     addrconf_prefix_route+0x1f4/0x2b4 net/ipv6/addrconf.c:2488
     addrconf_add_linklocal+0x238/0x378 net/ipv6/addrconf.c:3313
     addrconf_addr_gen+0x27c/0x2e0 net/ipv6/addrconf.c:-1
     addrconf_init_auto_addrs+0x390/0x764 net/ipv6/addrconf.c:-1
     addrconf_notify+0x7a0/0xbe4 net/ipv6/addrconf.c:3752
     notifier_call_chain+0x194/0x60c kernel/notifier.c:85
     raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:453
     call_netdevice_notifiers_info+0xb8/0x120 net/core/dev.c:2249
     call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
     call_netdevice_notifiers net/core/dev.c:2301 [inline]
     __dev_notify_flags+0x160/0x27c net/core/dev.c:9794
     netif_change_flags+0xd0/0x15c net/core/dev.c:9823
     do_setlink+0xab0/0x31c0 net/core/rtnetlink.c:3180
     rtnl_changelink net/core/rtnetlink.c:3799 [inline]
     __rtnl_newlink net/core/rtnetlink.c:3972 [inline]
     rtnl_newlink+0xd24/0x113c net/core/rtnetlink.c:4109

ref_tracker: netdev@00000000adbd14c8 has 1/7 users at
     __netdev_tracker_alloc include/linux/netdevice.h:4471 [inline]
     netdev_tracker_alloc include/linux/netdevice.h:4483 [inline]
     netdev_get_by_index+0x88/0xe0 net/core/dev.c:1027
     fib6_nh_init+0x258/0x14bc net/ipv6/route.c:3606
     ip6_route_info_create_nh+0x120/0x9a8 net/ipv6/route.c:3905
     addrconf_f6i_alloc+0x1e4/0x3b4 net/ipv6/route.c:4697
     ipv6_add_addr+0x458/0xd70 net/ipv6/addrconf.c:1126
     addrconf_add_linklocal+0x1e0/0x378 net/ipv6/addrconf.c:3311
     addrconf_addr_gen+0x27c/0x2e0 net/ipv6/addrconf.c:-1
     addrconf_init_auto_addrs+0x390/0x764 net/ipv6/addrconf.c:-1
     addrconf_notify+0x7a0/0xbe4 net/ipv6/addrconf.c:3752
     notifier_call_chain+0x194/0x60c kernel/notifier.c:85
     raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:453
     call_netdevice_notifiers_info+0xb8/0x120 net/core/dev.c:2249
     call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
     call_netdevice_notifiers net/core/dev.c:2301 [inline]
     __dev_notify_flags+0x160/0x27c net/core/dev.c:9794
     netif_change_flags+0xd0/0x15c net/core/dev.c:9823
     do_setlink+0xab0/0x31c0 net/core/rtnetlink.c:3180
     rtnl_changelink net/core/rtnetlink.c:3799 [inline]
     __rtnl_newlink net/core/rtnetlink.c:3972 [inline]
     rtnl_newlink+0xd24/0x113c net/core/rtnetlink.c:4109

ref_tracker: netdev@00000000adbd14c8 has 1/7 users at
     __netdev_tracker_alloc include/linux/netdevice.h:4471 [inline]
     netdev_tracker_alloc include/linux/netdevice.h:4483 [inline]
     netdev_get_by_index+0x88/0xe0 net/core/dev.c:1027
     fib6_nh_init+0x258/0x14bc net/ipv6/route.c:3606
     ip6_route_info_create_nh+0x120/0x9a8 net/ipv6/route.c:3905
     ip6_route_add+0x8c/0x1b4 net/ipv6/route.c:3957
     addrconf_add_mroute+0x14c/0x1cc net/ipv6/addrconf.c:2552
     addrconf_add_dev+0xe8/0x1a0 net/ipv6/addrconf.c:2570
     addrconf_dev_config net/ipv6/addrconf.c:3484 [inline]
     addrconf_init_auto_addrs+0x304/0x764 net/ipv6/addrconf.c:3572
     addrconf_notify+0x7a0/0xbe4 net/ipv6/addrconf.c:3752
     notifier_call_chain+0x194/0x60c kernel/notifier.c:85
     raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:453
     call_netdevice_notifiers_info+0xb8/0x120 net/core/dev.c:2249
     call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
     call_netdevice_notifiers net/core/dev.c:2301 [inline]
     __dev_notify_flags+0x160/0x27c net/core/dev.c:9794
     netif_change_flags+0xd0/0x15c net/core/dev.c:9823
     do_setlink+0xab0/0x31c0 net/core/rtnetlink.c:3180
     rtnl_changelink net/core/rtnetlink.c:3799 [inline]
     __rtnl_newlink net/core/rtnetlink.c:3972 [inline]
     rtnl_newlink+0xd24/0x113c net/core/rtnetlink.c:4109
     rtnetlink_rcv_msg+0x64c/0x984 net/core/rtnetlink.c:6995

ref_tracker: netdev@00000000adbd14c8 has 1/7 users at
     __netdev_tracker_alloc include/linux/netdevice.h:4471 [inline]
     netdev_tracker_alloc include/linux/netdevice.h:4483 [inline]
     netdev_get_by_index+0x88/0xe0 net/core/dev.c:1027
     fib6_nh_init+0x258/0x14bc net/ipv6/route.c:3606
     ip6_route_info_create_nh+0x120/0x9a8 net/ipv6/route.c:3905
     ip6_route_add+0x8c/0x1b4 net/ipv6/route.c:3957
     addrconf_prefix_route+0x1f4/0x2b4 net/ipv6/addrconf.c:2488
     fixup_permanent_addr net/ipv6/addrconf.c:3603 [inline]
     addrconf_permanent_addr+0x5a8/0x824 net/ipv6/addrconf.c:3639
     addrconf_notify+0x690/0xbe4 net/ipv6/addrconf.c:3706
     notifier_call_chain+0x194/0x60c kernel/notifier.c:85
     raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:453
     call_netdevice_notifiers_info+0xb8/0x120 net/core/dev.c:2249
     call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
     call_netdevice_notifiers net/core/dev.c:2301 [inline]
     __dev_notify_flags+0x160/0x27c net/core/dev.c:9794
     netif_change_flags+0xd0/0x15c net/core/dev.c:9823
     do_setlink+0xab0/0x31c0 net/core/rtnetlink.c:3180
     rtnl_changelink net/core/rtnetlink.c:3799 [inline]
     __rtnl_newlink net/core/rtnetlink.c:3972 [inline]
     rtnl_newlink+0xd24/0x113c net/core/rtnetlink.c:4109
     rtnetlink_rcv_msg+0x64c/0x984 net/core/rtnetlink.c:6995
     netlink_rcv_skb+0x22c/0x410 net/netlink/af_netlink.c:2550

ref_tracker: netdev@00000000adbd14c8 has 1/7 users at
     __netdev_tracker_alloc include/linux/netdevice.h:4471 [inline]
     netdev_hold include/linux/netdevice.h:4500 [inline]
     fib_check_nh_nongw net/ipv4/fib_semantics.c:1261 [inline]
     fib_check_nh+0x968/0x1548 net/ipv4/fib_semantics.c:1281
     fib_create_info+0x13d8/0x2100 net/ipv4/fib_semantics.c:1501
     fib_table_insert+0xa4/0x11e8 net/ipv4/fib_trie.c:1212
     fib_magic+0x26c/0x344 net/ipv4/fib_frontend.c:1134
     fib_add_ifaddr+0x334/0x4e4 net/ipv4/fib_frontend.c:1178
     fib_netdev_event+0x35c/0x49c net/ipv4/fib_frontend.c:1516
     notifier_call_chain+0x194/0x60c kernel/notifier.c:85
     raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:453
     call_netdevice_notifiers_info+0xb8/0x120 net/core/dev.c:2249
     call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
     call_netdevice_notifiers net/core/dev.c:2301 [inline]
     __dev_notify_flags+0x160/0x27c net/core/dev.c:9794
     netif_change_flags+0xd0/0x15c net/core/dev.c:9823
     do_setlink+0xab0/0x31c0 net/core/rtnetlink.c:3180
     rtnl_changelink net/core/rtnetlink.c:3799 [inline]
     __rtnl_newlink net/core/rtnetlink.c:3972 [inline]
     rtnl_newlink+0xd24/0x113c net/core/rtnetlink.c:4109
     rtnetlink_rcv_msg+0x64c/0x984 net/core/rtnetlink.c:6995
     netlink_rcv_skb+0x22c/0x410 net/netlink/af_netlink.c:2550
     rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:7022

ref_tracker: netdev@00000000adbd14c8 has 1/7 users at
     __netdev_tracker_alloc include/linux/netdevice.h:4471 [inline]
     netdev_tracker_alloc include/linux/netdevice.h:4483 [inline]
     netdev_get_by_index+0x88/0xe0 net/core/dev.c:1027
     fib6_nh_init+0x258/0x14bc net/ipv6/route.c:3606
     ip6_route_info_create_nh+0x120/0x9a8 net/ipv6/route.c:3905
     addrconf_f6i_alloc+0x1e4/0x3b4 net/ipv6/route.c:4697
     ipv6_add_addr+0x458/0xd70 net/ipv6/addrconf.c:1126
     inet6_addr_add+0x2a4/0x78c net/ipv6/addrconf.c:3050
     inet6_rtm_newaddr+0x738/0xa58 net/ipv6/addrconf.c:5071
     rtnetlink_rcv_msg+0x64c/0x984 net/core/rtnetlink.c:6995
     netlink_rcv_skb+0x22c/0x410 net/netlink/af_netlink.c:2550
     rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:7022
     netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
     netlink_unicast+0x610/0x800 net/netlink/af_netlink.c:1344
     netlink_sendmsg+0x63c/0x920 net/netlink/af_netlink.c:1894
     sock_sendmsg_nosec net/socket.c:787 [inline]
     __sock_sendmsg+0xc8/0x138 net/socket.c:802
     __sys_sendto+0x254/0x338 net/socket.c:2265
     __do_sys_sendto net/socket.c:2272 [inline]
     __se_sys_sendto net/socket.c:2268 [inline]
     __arm64_sys_sendto+0xd8/0xf8 net/socket.c:2268
     __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
     invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49

ref_tracker: netdev@00000000adbd14c8 has 1/7 users at
     __netdev_tracker_alloc include/linux/netdevice.h:4471 [inline]
     netdev_tracker_alloc+0x68/0xb0 include/linux/netdevice.h:4483
     fib_create_info+0x1b14/0x2100 net/ipv4/fib_semantics.c:1495
     fib_table_insert+0xa4/0x11e8 net/ipv4/fib_trie.c:1212
     fib_magic+0x26c/0x344 net/ipv4/fib_frontend.c:1134
     fib_add_ifaddr+0x118/0x4e4 net/ipv4/fib_frontend.c:1156
     fib_inetaddr_event+0x114/0x1c0 net/ipv4/fib_frontend.c:1470
     notifier_call_chain+0x194/0x60c kernel/notifier.c:85
     blocking_notifier_call_chain+0x70/0xa0 kernel/notifier.c:380
     __inet_insert_ifa+0x828/0xa0c net/ipv4/devinet.c:566
     inet_rtm_newaddr+0xb58/0x10e8 net/ipv4/devinet.c:1001
     rtnetlink_rcv_msg+0x64c/0x984 net/core/rtnetlink.c:6995
     netlink_rcv_skb+0x22c/0x410 net/netlink/af_netlink.c:2550
     rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:7022
     netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
     netlink_unicast+0x610/0x800 net/netlink/af_netlink.c:1344
     netlink_sendmsg+0x63c/0x920 net/netlink/af_netlink.c:1894
     sock_sendmsg_nosec net/socket.c:787 [inline]
     __sock_sendmsg+0xc8/0x138 net/socket.c:802



Tested on:

commit:         5cbb61bf arm64/fpsimd: ptrace: zero target's fpsimd_st..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=15f620ec580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a834c6344141a58b
dashboard link: https://syzkaller.appspot.com/bug?extid=e2af46126e0644cbebdd
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

Note: no patches were applied.