syzbot

netlink: 68 bytes leftover after parsing attributes in process `syz-executor0'.
INFO: task syz-executor2:30220 blocked for more than 140 seconds.
      Not tainted 4.9.131+ #50
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor2   D26232 30220  18056 0x00000004
 ffff8801a882af80 0000000000000000 ffff8801c7311b80 ffffffff83029180
 ffff8801db621018 ffff88017d00f160 ffffffff827f3542 ffff88017d00f100
 ffffffff82802f48 ffff8801db621000 00ff88017d00f158 ffff8801db6218f0
Call Trace:
 [<ffffffff827f4a6f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff82800215>] schedule_timeout+0x735/0xe20 kernel/time/timer.c:1771
 [<ffffffff827f2d0a>] io_schedule_timeout+0x1ba/0x390 kernel/sched/core.c:5176
 [<ffffffff815d6854>] io_schedule include/linux/sched.h:460 [inline]
 [<ffffffff815d6854>] dio_await_one fs/direct-io.c:461 [inline]
 [<ffffffff815d6854>] dio_await_completion fs/direct-io.c:515 [inline]
 [<ffffffff815d6854>] do_blockdev_direct_IO fs/direct-io.c:1331 [inline]
 [<ffffffff815d6854>] __blockdev_direct_IO+0x8b54/0xbd10 fs/direct-io.c:1360
 [<ffffffff816de338>] ext4_direct_IO_write fs/ext4/inode.c:3507 [inline]
 [<ffffffff816de338>] ext4_direct_IO+0x978/0x29c0 fs/ext4/inode.c:3663
 [<ffffffff81411fd4>] generic_file_direct_write+0x284/0x510 mm/filemap.c:2655
 [<ffffffff8141247f>] __generic_file_write_iter+0x21f/0x540 mm/filemap.c:2835
 [<ffffffff816b32ad>] ext4_file_write_iter+0x63d/0xd70 fs/ext4/file.c:165
 [<ffffffff815fb6f2>] aio_write+0x2f2/0x510 fs/aio.c:1505
 [<ffffffff816002b5>] io_submit_one fs/aio.c:1586 [inline]
 [<ffffffff816002b5>] do_io_submit+0xd35/0x1080 fs/aio.c:1654
 [<ffffffff81003e2e>] exit_to_usermode_loop+0x10e/0x150 arch/x86/entry/common.c:158
 [<ffffffff81005932>] prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 [<ffffffff81005932>] syscall_return_slowpath arch/x86/entry/common.c:263 [inline]
 [<ffffffff81005932>] do_syscall_64+0x3e2/0x550 arch/x86/entry/common.c:290
 [<ffffffff828037d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/24:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131bbcc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131bbcc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.?..}, at: [<ffffffff813fe394>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/1896:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff8156cdac>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/2024:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82801892>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81d2b2b2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor4/29291:
 #0:  (sb_writers#4){.+.+.+}, at: [<ffffffff8150de40>] file_start_write include/linux/fs.h:2640 [inline]
 #0:  (sb_writers#4){.+.+.+}, at: [<ffffffff8150de40>] do_sendfile+0xa80/0xc30 fs/read_write.c:1392

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

NMI backtrace for cpu 1
CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.131+ #50
 ffff8801d9907d08 ffffffff81b37029 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff81098450 ffff8801d9907d40
 ffffffff81b42139 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81b37029>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81b37029>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81b42139>] nmi_cpu_backtrace.cold.0+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81b420cc>] nmi_trigger_cpumask_backtrace+0x12c/0x151 lib/nmi_backtrace.c:60
 [<ffffffff81098554>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff8131c15d>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff8131c15d>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8131c15d>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8131c15d>] watchdog+0x6ad/0xa20 kernel/hung_task.c:239
 [<ffffffff811429fd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff8280399c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff828023d6