Subject: Re: [syzbot] [net?] INFO: task hung in addrconf_dad_work (5)

From: syzbot <[email-masked]>
Date: Sun, 22 Sep 2024 23:55:27 -0700

syzbot has found a reproducer for the following issue on:

HEAD commit:    af9c191ac2a0 Merge tag 'trace-ring-buffer-v6.12' of git://..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=148aa19f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=74ffdb3b3fad1a43
dashboard link: https://syzkaller.appspot.com/bug?extid=82ccd564344eeaa5427d
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=162e9c27980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1123c107980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d3f6f73cc34a/disk-af9c191a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a5895312beb3/vmlinux-af9c191a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c737e741d8d8/bzImage-af9c191a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

INFO: task kworker/R-ipv6_:2724 blocked for more than 147 seconds.
      Not tainted 6.11.0-syzkaller-08829-gaf9c191ac2a0 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/R-ipv6_ state:D stack:28560 pid:2724  tgid:2724  ppid:2      flags:0x00004000
Workqueue: ipv6_addrconf addrconf_dad_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5315 [inline]
 __schedule+0x1843/0x4ae0 kernel/sched/core.c:6674
 __schedule_loop kernel/sched/core.c:6751 [inline]
 schedule+0x14b/0x320 kernel/sched/core.c:6766
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6823
 __mutex_lock_common kernel/locking/mutex.c:684 [inline]
 __mutex_lock+0x6a7/0xd70 kernel/locking/mutex.c:752
 addrconf_dad_work+0xd0/0x16f0 net/ipv6/addrconf.c:4196
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
 rescuer_thread+0x63f/0x10a0 kernel/workqueue.c:3487
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
INFO: task syz-executor183:5220 blocked for more than 150 seconds.
      Not tainted 6.11.0-syzkaller-08829-gaf9c191ac2a0 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor183 state:D stack:20192 pid:5220  tgid:5220  ppid:5219   flags:0x00000002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5315 [inline]
 __schedule+0x1843/0x4ae0 kernel/sched/core.c:6674
 __schedule_loop kernel/sched/core.c:6751 [inline]
 schedule+0x14b/0x320 kernel/sched/core.c:6766
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6823
 __mutex_lock_common kernel/locking/mutex.c:684 [inline]
 __mutex_lock+0x6a7/0xd70 kernel/locking/mutex.c:752
 rtnl_lock net/core/rtnetlink.c:79 [inline]
 rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6643
 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
 netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357
 netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:745
 __sys_sendto+0x398/0x4f0 net/socket.c:2210
 __do_sys_sendto net/socket.c:2222 [inline]
 __se_sys_sendto net/socket.c:2218 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2218
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4abeb91463
RSP: 002b:00007fff6c3ace18 EFLAGS: 00000202 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f4abec14560 RCX: 00007f4abeb91463
RDX: 0000000000000040 RSI: 00007f4abec145b0 RDI: 0000000000000003
RBP: 0000000000000003 R08: 00007fff6c3ace34 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000001
R13: 0000000000000000 R14: 00007f4abec145b0 R15: 0000000000000000
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/1:0/25:
 #0: ffff88801ac80948 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
 #0: ffff88801ac80948 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1850 kernel/workqueue.c:3310
 #1: ffffc900001f7d00 (reg_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
 #1: ffffc900001f7d00 (reg_work){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1850 kernel/workqueue.c:3310
 #2: ffffffff8fcb97c8 (rtnl_mutex){+.+.}-{3:3}, at: reg_todo+0x1c/0x8d0 net/wireless/reg.c:3218
1 lock held by khungtaskd/30:
 #0: ffffffff8e937ee0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 #0: ffffffff8e937ee0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8e937ee0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6701
3 locks held by kworker/u8:2/35:
 #0: ffff88801ac89148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
 #0: ffff88801ac89148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1850 kernel/workqueue.c:3310
 #1: ffffc90000ab7d00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
 #1: ffffc90000ab7d00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1850 kernel/workqueue.c:3310
 #2: ffffffff8fcb97c8 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:276
4 locks held by kworker/u8:3/52:
7 locks held by kworker/u8:5/74:
3 locks held by kworker/R-ipv6_/2724:
 #0: ffff88814bba0948 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
 #0: ffff88814bba0948 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1850 kernel/workqueue.c:3310
 #1: ffffc90009497c80 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
 #1: ffffc90009497c80 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1850 kernel/workqueue.c:3310
 #2: ffffffff8fcb97c8 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xd0/0x16f0 net/ipv6/addrconf.c:4196
4 locks held by kworker/1:2/3197:
1 lock held by syslogd/4651:
1 lock held by klogd/4658:
5 locks held by udevd/4669:
3 locks held by dhcpcd/4883:
2 locks held by getty/4972:
 #0: ffff888032e120a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90002f062f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6a6/0x1e00 drivers/tty/n_tty.c:2211
1 lock held by syz-executor183/5213:
 #0: ffffffff8fcb97c8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
 #0: ffffffff8fcb97c8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6643
4 locks held by syz-executor183/5216:
1 lock held by syz-executor183/5217:
 #0: ffffffff8fcb97c8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
 #0: ffffffff8fcb97c8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6643
1 lock held by syz-executor183/5220:
 #0: ffffffff8fcb97c8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
 #0: ffffffff8fcb97c8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6643
4 locks held by syz-executor183/5221:
2 locks held by dhcpcd/5267:
 #0: ffff888067190258 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1609 [inline]
 #0: ffff888067190258 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x32/0xcb0 net/packet/af_packet.c:3266
 #1: ffffffff8e93d478 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:297 [inline]
 #1: ffffffff8e93d478 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x381/0x830 kernel/rcu/tree_exp.h:976

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