syzbot

INFO: task syz.0.17:5971 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:27848 pid:5971  tgid:5971  ppid:5760   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5504 [inline]
 __schedule+0x125c/0x6730 kernel/sched/core.c:7228
 __schedule_loop kernel/sched/core.c:7307 [inline]
 schedule+0xdd/0x390 kernel/sched/core.c:7322
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7379
 rwsem_down_write_slowpath+0x4c2/0x12b0 kernel/locking/rwsem.c:1215
 __down_write_common kernel/locking/rwsem.c:1347 [inline]
 __down_write kernel/locking/rwsem.c:1356 [inline]
 down_write+0x1c7/0x1f0 kernel/locking/rwsem.c:1632
 inode_lock include/linux/fs.h:1029 [inline]
 blkdev_fallocate+0x24b/0x440 block/fops.c:882
 vfs_fallocate+0x576/0x10a0 fs/open.c:338
 ksys_fallocate fs/open.c:362 [inline]
 __do_sys_fallocate fs/open.c:367 [inline]
 __se_sys_fallocate fs/open.c:365 [inline]
 __x64_sys_fallocate+0xd5/0x140 fs/open.c:365
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0b0179ce59
RSP: 002b:00007ffcffb61518 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007f0b01a15fa0 RCX: 00007f0b0179ce59
RDX: 0000000000000000 RSI: 0000000000000010 RDI: 0000000000000004
RBP: 00007f0b01832e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000002000000400 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0b01a15fac R14: 00007f0b01a15fa0 R15: 00007f0b01a15fa0
 </TASK>
INFO: task syz.4.21:5972 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.21        state:D stack:28264 pid:5972  tgid:5972  ppid:5771   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5504 [inline]
 __schedule+0x125c/0x6730 kernel/sched/core.c:7228
 __schedule_loop kernel/sched/core.c:7307 [inline]
 schedule+0xdd/0x390 kernel/sched/core.c:7322
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7379
 rwsem_down_write_slowpath+0x4c2/0x12b0 kernel/locking/rwsem.c:1215
 __down_write_common kernel/locking/rwsem.c:1347 [inline]
 __down_write kernel/locking/rwsem.c:1356 [inline]
 down_write+0x1c7/0x1f0 kernel/locking/rwsem.c:1632
 inode_lock include/linux/fs.h:1029 [inline]
 blkdev_fallocate+0x24b/0x440 block/fops.c:882
 vfs_fallocate+0x576/0x10a0 fs/open.c:338
 ksys_fallocate fs/open.c:362 [inline]
 __do_sys_fallocate fs/open.c:367 [inline]
 __se_sys_fallocate fs/open.c:365 [inline]
 __x64_sys_fallocate+0xd5/0x140 fs/open.c:365
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6fd399ce59
RSP: 002b:00007ffc6df3fd68 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007f6fd3c15fa0 RCX: 00007f6fd399ce59
RDX: 0000000000000000 RSI: 0000000000000010 RDI: 0000000000000004
RBP: 00007f6fd3a32e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000002000000400 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6fd3c15fac R14: 00007f6fd3c15fa0 R15: 00007f6fd3c15fa0
 </TASK>
INFO: lockdep is turned off.
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x1d7/0x230 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+0x141/0x190 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xcb1/0x1030 kernel/hung_task.c:561
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 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: 6352 Comm: kworker/u8:9 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: udp_tunnel_nic udp_tunnel_nic_device_sync_work
RIP: 0010:io_serial_in+0x87/0xb0 drivers/tty/serial/8250/8250_port.c:402
Code: 34 84 fc 48 8d 7d 40 44 89 e1 48 b8 00 00 00 00 00 fc ff df 48 89 fa d3 e3 48 c1 ea 03 80 3c 02 00 75 1a 66 03 5d 40 89 da ec <5b> 0f b6 c0 5d 41 5c c3 cc cc cc cc e8 d8 a4 f4 fc eb a2 e8 61 a5
RSP: 0018:ffffc90004b3f2a8 EFLAGS: 00000002
RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: ffffffff85852a40 RDI: ffffffff9b4c8580
RBP: ffffffff9b4c8540 R08: 0000000000000001 R09: 000000000000001f
R10: 0000000000000000 R11: 205d313354202020 R12: 0000000000000000
R13: 0000000000000020 R14: fffffbfff3699102 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff88812441a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa8d066b6b0 CR3: 000000002b678000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 serial_in drivers/tty/serial/8250/8250.h:128 [inline]
 serial_lsr_in drivers/tty/serial/8250/8250.h:150 [inline]
 wait_for_lsr+0x13a/0x210 drivers/tty/serial/8250/8250_port.c:1973
 serial8250_fifo_wait_for_lsr_thre drivers/tty/serial/8250/8250_port.c:3210 [inline]
 serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3275 [inline]
 serial8250_console_write+0xdb9/0x1900 drivers/tty/serial/8250/8250_port.c:3360
 console_emit_next_record kernel/printk/printk.c:3183 [inline]
 console_flush_one_record+0x790/0xe50 kernel/printk/printk.c:3269
 console_flush_all kernel/printk/printk.c:3343 [inline]
 __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
 console_unlock+0x103/0x260 kernel/printk/printk.c:3413
 vprintk_emit+0x407/0x6b0 kernel/printk/printk.c:2479
 dev_vprintk_emit+0x391/0x3e0 drivers/base/core.c:4996
 dev_printk_emit+0xd2/0x10d drivers/base/core.c:5007
 __netdev_printk+0x1d1/0x290 net/core/dev.c:12956
 netdev_info+0xef/0x127 net/core/dev.c:13011
 nsim_udp_tunnel_set_port.cold+0x96/0xc7 drivers/net/netdevsim/udp_tunnels.c:31
 udp_tunnel_nic_device_sync_one net/ipv4/udp_tunnel_nic.c:228 [inline]
 udp_tunnel_nic_device_sync_by_port net/ipv4/udp_tunnel_nic.c:249 [inline]
 __udp_tunnel_nic_device_sync.part.0+0x982/0xdf0 net/ipv4/udp_tunnel_nic.c:292
 __udp_tunnel_nic_device_sync net/ipv4/udp_tunnel_nic.c:740 [inline]
 udp_tunnel_nic_device_sync_work+0xb3/0xa50 net/ipv4/udp_tunnel_nic.c:740
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>