syzbot

INFO: task syz.0.3837:13836 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.3837      state:D stack:27032 pid:13836 tgid:13835 ppid:5624   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5388 [inline]
 __schedule+0x16ec/0x5620 kernel/sched/core.c:7189
 __schedule_loop kernel/sched/core.c:7268 [inline]
 rt_mutex_schedule+0x76/0xf0 kernel/sched/core.c:7564
 rt_mutex_slowlock_block+0x508/0x680 kernel/locking/rtmutex.c:1662
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1739 [inline]
 __rt_mutex_slowlock_locked kernel/locking/rtmutex.c:1779 [inline]
 rt_mutex_slowlock+0x2dc/0x780 kernel/locking/rtmutex.c:1819
 __rt_mutex_lock kernel/locking/rtmutex.c:1834 [inline]
 __mutex_lock_common kernel/locking/rtmutex_api.c:535 [inline]
 mutex_lock_nested+0x168/0x1d0 kernel/locking/rtmutex_api.c:553
 nfsd_nl_threads_get_doit+0x1c0/0x790 fs/nfsd/nfsctl.c:1738
 genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1114
 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
 genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1209
 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2555
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x780/0x920 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1899
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 ____sys_sendmsg+0x94c/0x9c0 net/socket.c:2698
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2752
 __sys_sendmsg net/socket.c:2784 [inline]
 __do_sys_sendmsg net/socket.c:2789 [inline]
 __se_sys_sendmsg net/socket.c:2787 [inline]
 __x64_sys_sendmsg+0x1c3/0x2a0 net/socket.c:2787
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2fb523ce59
RSP: 002b:00007f2fb348e028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f2fb54b5fa0 RCX: 00007f2fb523ce59
RDX: 0000000004008090 RSI: 0000200000000140 RDI: 0000000000000003
RBP: 00007f2fb52d2d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2fb54b6038 R14: 00007f2fb54b5fa0 R15: 00007ffd369738c8
 </TASK>

Showing all locks held in the system:
1 lock held by ktimers/1/29:
 #0: ffff8880b893b860 (&rq->__lock){-...}-{2:2}, at: raw_spin_rq_lock_nested+0x31/0x150 kernel/sched/core.c:652
6 locks held by kworker/1:1/36:
 #0: ffff88801f2d6938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #0: ffff88801f2d6938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860 kernel/workqueue.c:3397
 #1: ffffc90000ad7c40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3290 [inline]
 #1: ffffc90000ad7c40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860 kernel/workqueue.c:3397
 #2: ffff88802a822210 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1040 [inline]
 #2: ffff88802a822210 (&dev->mutex){....}-{4:4}, at: hub_event+0x17c/0x4f60 drivers/usb/core/hub.c:5899
 #3: ffff8880609fe210 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1040 [inline]
 #3: ffff8880609fe210 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x450 drivers/base/dd.c:1076
 #4: ffff8880608291d8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1040 [inline]
 #4: ffff8880608291d8 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x450 drivers/base/dd.c:1076
 #5: ffff888039348f78 (&d->usb_mutex#2){+.+.}-{4:4}, at: gp8psk_usb_in_op+0x89/0x220 drivers/media/usb/dvb-usb/gp8psk.c:38
1 lock held by khungtaskd/38:
 #0: ffffffff8dfc8000 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8dfc8000 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
 #0: ffffffff8dfc8000 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
4 locks held by kworker/u8:8/1043:
2 locks held by getty/5357:
 #0: ffff8880292ce0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003cbe2e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x462/0x13a0 drivers/tty/n_tty.c:2211
1 lock held by syz-executor/5615:
 #0: ffff888036c1a480 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
4 locks held by kworker/0:7/5976:
 #0: ffff88801a037938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #0: ffff88801a037938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860 kernel/workqueue.c:3397
 #1: ffffc90005f0fc40 ((work_completion)(&helper->damage_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3290 [inline]
 #1: ffffc90005f0fc40 ((work_completion)(&helper->damage_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860 kernel/workqueue.c:3397
 #2: ffff888026318aa0 (&helper->lock){+.+.}-{4:4}, at: drm_fb_helper_fb_dirty drivers/gpu/drm/drm_fb_helper.c:236 [inline]
 #2: ffff888026318aa0 (&helper->lock){+.+.}-{4:4}, at: drm_fb_helper_damage_work+0x125/0x6f0 drivers/gpu/drm/drm_fb_helper.c:275
 #3: ffff888026312158 (&dev->master_mutex){+.+.}-{4:4}, at: drm_master_internal_acquire+0x20/0x80 drivers/gpu/drm/drm_auth.c:435
1 lock held by udevd/5987:
 #0: ffff8880380c4480 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
2 locks held by syz.4.2716/11391:
 #0: ffffffff8f3bfc40 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
 #1: ffffffff8e2e84d8 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_set_doit+0x13e/0x1630 fs/nfsd/nfsctl.c:1948
2 locks held by syz.0.3837/13836:
 #0: ffffffff8f3bfc40 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
 #1: ffffffff8e2e84d8 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_threads_get_doit+0x1c0/0x790 fs/nfsd/nfsctl.c:1738
1 lock held by syz-executor/14215:
 #0: ffff88802b878480 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
2 locks held by syz.1.4039/14296:
 #0: ffffffff8f3bfc40 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
 #1: ffffffff8e2e84d8 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_set_doit+0x13e/0x1630 fs/nfsd/nfsctl.c:1948
1 lock held by syz-executor/14625:
5 locks held by syz.2.5655/17770:

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 38 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x135/0x170 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xfd3/0x1030 kernel/hung_task.c:561
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 5987 Comm: udevd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:lookup_chain_cache kernel/locking/lockdep.c:3801 [inline]
RIP: 0010:lookup_chain_cache_add kernel/locking/lockdep.c:3821 [inline]
RIP: 0010:validate_chain kernel/locking/lockdep.c:3876 [inline]
RIP: 0010:__lock_acquire+0xb17/0x2cf0 kernel/locking/lockdep.c:5237
Code: 4e eb 0d 48 c7 c6 30 42 71 8d 67 48 0f b9 3a 90 48 bb eb 83 b5 80 46 86 c8 61 48 0f af dd 48 c1 eb 2d 48 8b 04 dd 60 93 2d 93 <48> 85 c0 0f 94 c1 48 83 c0 f8 0f 94 c2 08 ca 0f 84 1c 01 00 00 e8
RSP: 0018:ffffc9000611f9f8 EFLAGS: 00000006
RAX: ffffffff9384f438 RBX: 0000000000020fd2 RCX: 0000000000040000
RDX: 000000005f69be49 RSI: 00000000a77be0ee RDI: ffff8880318d0000
RBP: b6f06d952a81306a R08: ffffffff82400a48 R09: ffff88803f881e48
R10: dffffc0000000000 R11: fffffbfff1f10c7f R12: ffff8880318d0c20
R13: ffff8880318d0c20 R14: ffff8880318d0000 R15: 0000000000000001
FS:  00007f4ca9f04880(0000) GS:ffff888126283000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2e821ff8 CR3: 000000003ceba000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 rt_spin_lock+0x83/0x400 kernel/locking/spinlock_rt.c:56
 spin_lock include/linux/spinlock_rt.h:45 [inline]
 __dentry_kill+0x268/0x690 fs/dcache.c:729
 finish_dput+0xc9/0x480 fs/dcache.c:927
 end_renaming fs/namei.c:4124 [inline]
 filename_renameat2+0x61e/0x9c0 fs/namei.c:6174
 __do_sys_rename fs/namei.c:6216 [inline]
 __se_sys_rename+0x55/0x2c0 fs/namei.c:6212
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4ca9fc5cc7
Code: e8 5e a7 09 00 f7 d8 19 c0 5b c3 0f 1f 84 00 00 00 00 00 b8 ff ff ff ff 5b c3 66 0f 1f 84 00 00 00 00 00 b8 52 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 8b 15 01 61 17 00 f7 d8 64 89 02 b8
RSP: 002b:00007ffca0e1ad68 EFLAGS: 00000206 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 00005633e6d4c0d0 RCX: 00007f4ca9fc5cc7
RDX: 00005633e6d2a010 RSI: 00007ffca0e1ad80 RDI: 00007ffca0e1b180
RBP: 00005633e6d59f10 R08: 00000000000001e0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 00007ffca0e1ad80
R13: 00007ffca0e1b180 R14: 0000000000000000 R15: 00005633b70e29dd
 </TASK>