syzbot

INFO: task syz.2.359:11004 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.359       state:D stack:26856 pid:11004 tgid:11001 ppid:10569  task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x16f3/0x4c20 kernel/sched/core.c:6929
 __schedule_loop kernel/sched/core.c:7011 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7026
 percpu_rwsem_wait+0x2e6/0x330 kernel/locking/percpu-rwsem.c:164
 __percpu_down_read+0xfc/0x140 kernel/locking/percpu-rwsem.c:180
 percpu_down_read_internal include/linux/percpu-rwsem.h:67 [inline]
 percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
 __sb_start_write include/linux/fs.h:1916 [inline]
 sb_start_write+0x18e/0x1c0 include/linux/fs.h:2052
 mnt_want_write+0x41/0x90 fs/namespace.c:499
 do_unlinkat+0x131/0x570 fs/namei.c:4720
 __do_sys_unlinkat fs/namei.c:4778 [inline]
 __se_sys_unlinkat fs/namei.c:4771 [inline]
 __x64_sys_unlinkat+0xd3/0xf0 fs/namei.c:4771
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb7b799f749
RSP: 002b:00007fb7b5be5038 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 00007fb7b7bf6090 RCX: 00007fb7b799f749
RDX: 0000000000000000 RSI: 0000200000000c40 RDI: ffffffffffffff9c
RBP: 00007fb7b7a23f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb7b7bf6128 R14: 00007fb7b7bf6090 R15: 00007ffd9feba228
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/0:1/10:
2 locks held by kworker/u8:1/13:
1 lock held by khungtaskd/38:
 #0: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
 #0: ffffffff8d5aa880 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
1 lock held by dhcpcd/5463:
2 locks held by getty/5560:
 #0: ffff88823bf3e8a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003e832e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x444/0x1400 drivers/tty/n_tty.c:2222
3 locks held by kworker/0:5/9986:
5 locks held by kworker/u8:2/10009:
1 lock held by syz.2.359/11004:
 #0: ffff88804c9b4480 (sb_writers#24){++++}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:499
4 locks held by kworker/u8:14/11231:
4 locks held by syz-executor/12485:
 #0: ffff888033f50480 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3113 [inline]
 #0: ffff888033f50480 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x217/0xb40 fs/read_write.c:682
 #1: ffff8880695f1078 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:343
 #2: ffff8880266c7008 (kn->active#53){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff8880266c7008 (kn->active#53){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x232/0x540 fs/kernfs/file.c:344
 #3: ffffffff8e0f4738 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: new_device_store+0x12c/0x6f0 drivers/net/netdevsim/bus.c:184
2 locks held by syz-executor/12553:
8 locks held by syz-executor/12578:
1 lock held by udevd/12607:
4 locks held by syz-executor/12609:
 #0: ffff888033f50480 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3113 [inline]
 #0: ffff888033f50480 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x217/0xb40 fs/read_write.c:682
 #1: ffff888035c07878 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:343
 #2: ffff8880266c70f8 (kn->active#52){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff8880266c70f8 (kn->active#52){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x232/0x540 fs/kernfs/file.c:344
 #3: ffffffff8e0f4738 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: del_device_store+0xd1/0x360 drivers/net/netdevsim/bus.c:234
6 locks held by modprobe/12721:

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

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 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:332 [inline]
 watchdog+0xf60/0xfa0 kernel/hung_task.c:495
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 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: 101 PID: 5462 Comm: dhcpcd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0033:0x5631a63782b4
Code: 70 38 31 c9 49 89 e8 ba 02 10 00 00 48 89 df e8 72 d9 ff ff 48 83 f8 ff 74 1c 31 d2 31 f6 48 89 df e8 c0 f4 ff ff 48 83 c4 08 <5b> 5d c3 66 0f 1f 84 00 00 00 00 00 b8 ff ff ff ff eb e9 66 0f 1f
RSP: 002b:00007fffba1ff918 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 00007fffba200320 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 000000000000000a RDI: 00005631d4b0d390
RBP: 00007fffba1ff9a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000002
R13: 00005631d4c780b0 R14: 00007fffba200320 R15: 00005631d4d0dad0
FS:  00007ff8ef131740 GS:  0000000000000000