INFO: task kworker/0:0:6873 blocked for more than 143 seconds.
      Not tainted 5.9.0-rc8-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:0     state:D stack:29288 pid: 6873 ppid:     2 flags:0x00004000
Workqueue: ipv6_addrconf addrconf_verify_work
Call Trace:
 context_switch kernel/sched/core.c:3778 [inline]
 __schedule+0xec9/0x2280 kernel/sched/core.c:4527
 schedule+0xd0/0x2a0 kernel/sched/core.c:4602
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:4661
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x3e2/0x10e0 kernel/locking/mutex.c:1103
 addrconf_verify_work+0xa/0x20 net/ipv6/addrconf.c:4568
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Showing all locks held in the system:
1 lock held by khungtaskd/1169:
 #0: ffffffff8a067f40 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5852
1 lock held by in:imklog/6571:
 #0: ffff88809f0d8b30 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:930
3 locks held by kworker/0:0/6873:
 #0: ffff88809a0ef138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: ffff88809a0ef138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
 #0: ffff88809a0ef138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
 #0: ffff88809a0ef138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
 #0: ffff88809a0ef138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
 #0: ffff88809a0ef138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x82b/0x1670 kernel/workqueue.c:2240
 #1: ffffc900060b7da8 ((addr_chk_work).work){+.+.}-{0:0}, at: process_one_work+0x85f/0x1670 kernel/workqueue.c:2244
 #2: ffffffff8b150948 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_verify_work+0xa/0x20 net/ipv6/addrconf.c:4568
2 locks held by syz-executor544/6903:

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 1169 Comm: khungtaskd Not tainted 5.9.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fd lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1b3/0x223 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:209 [inline]
 watchdog+0xd7d/0x1000 kernel/hung_task.c:295
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 3914 Comm: systemd-journal Not tainted 5.9.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:write_comp_data+0x2f/0x80 kernel/kcov.c:218
Code: 05 46 c4 8b 7e 65 48 8b 34 25 c0 fe 01 00 a9 00 01 ff 00 74 0f f6 c4 01 74 59 8b 86 2c 14 00 00 85 c0 74 4f 8b 86 08 14 00 00 <83> f8 03 75 44 48 8b 86 10 14 00 00 8b b6 0c 14 00 00 4c 8b 00 48
RSP: 0018:ffffc90001027de8 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817c0e61
RDX: 0000000000000000 RSI: ffff8880933040c0 RDI: 0000000000000005
RBP: ffff8880aa06f900 R08: 0000000000000001 R09: ffffffff8a012f5b
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000286
R13: ffff88809f623610 R14: 0000000000000200 R15: 0000000000000000
FS:  00007fdd639bc8c0(0000) GS:ffff8880ae400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdd60d5b000 CR3: 0000000092cb0000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 trace_hardirqs_off+0x51/0x210 kernel/trace/trace_preemptirq.c:81
 kmem_cache_free.part.0+0x15b/0x1e0 mm/slab.c:3693
 __put_cred+0x1de/0x250 kernel/cred.c:148
 put_cred include/linux/cred.h:287 [inline]
 put_cred include/linux/cred.h:280 [inline]
 revert_creds+0x1a8/0x1f0 kernel/cred.c:598
 do_faccessat+0x2ca/0x820 fs/open.c:464
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fdd62c789c7
Code: 83 c4 08 48 3d 01 f0 ff ff 73 01 c3 48 8b 0d c8 d4 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 b8 15 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a1 d4 2b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffd41dadbf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000015
RAX: ffffffffffffffda RBX: 00007ffd41db0b10 RCX: 00007fdd62c789c7
RDX: 00007fdd636e9a00 RSI: 0000000000000000 RDI: 000055ead42c99a3
RBP: 00007ffd41dadc30 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000069 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ffd41db0b10 R15: 00007ffd41dae120