Not tainted 4.13.0-rc6-next-20170825+ #9 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syzkaller741492 D23824 3041 3039 0x00000000 Call Trace: context_switch kernel/sched/core.c:2792 [inline] __schedule+0x8e8/0x2070 kernel/sched/core.c:3371 schedule+0x108/0x440 kernel/sched/core.c:3430 __lock_sock+0x1dc/0x2f0 net/core/sock.c:2245 lock_sock_nested+0xf3/0x110 net/core/sock.c:2766 lock_sock include/net/sock.h:1459 [inline] tcp_sendmsg+0x21/0x50 net/ipv4/tcp.c:1447 inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:762 sock_sendmsg_nosec net/socket.c:633 [inline] sock_sendmsg+0xca/0x110 net/socket.c:643 kernel_sendmsg+0x47/0x60 net/socket.c:651 sock_no_sendpage+0x1cc/0x280 net/core/sock.c:2574 tcp_sendpage_locked+0x10b/0x160 net/ipv4/tcp.c:1055 tcp_sendpage+0x43/0x60 net/ipv4/tcp.c:1070 inet_sendpage+0x1aa/0x660 net/ipv4/af_inet.c:779 kernel_sendpage+0x8d/0xe0 net/socket.c:3387 sock_sendpage+0x92/0xc0 net/socket.c:858 pipe_to_sendpage+0x290/0x3b0 fs/splice.c:467 splice_from_pipe_feed fs/splice.c:518 [inline] __splice_from_pipe+0x343/0x750 fs/splice.c:642 splice_from_pipe+0x1e9/0x330 fs/splice.c:677 generic_splice_sendpage+0x40/0x50 fs/splice.c:848 do_splice_from fs/splice.c:867 [inline] do_splice fs/splice.c:1163 [inline] SYSC_splice fs/splice.c:1418 [inline] SyS_splice+0x7d5/0x1630 fs/splice.c:1398 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x434f29 RSP: 002b:00007ffdbde9e948 EFLAGS: 00000203 ORIG_RAX: 0000000000000113 RAX: ffffffffffffffda RBX: 00000000004002b0 RCX: 0000000000434f29 RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 0000000000000086 R08: 0000000000000009 R09: 0000000000000004 R10: 0000000000000000 R11: 0000000000000203 R12: 0000000000000000 R13: 00000000004018a0 R14: 0000000000401930 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/663: #0: (rcu_read_lock){....}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0xd2/0x410 kernel/locking/lockdep.c:4552 1 lock held by rsyslogd/2927: #0: (&f->f_pos_lock){+.+.}, at: [] __fdget_pos+0x131/0x1a0 fs/file.c:767 2 locks held by getty/3010: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/3011: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/3012: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/3013: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/3014: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/3015: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/3016: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by syzkaller741492/3041: #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock_nested fs/pipe.c:66 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock+0x56/0x70 fs/pipe.c:74 #1: (sk_lock-AF_INET){+.+.}, at: [] lock_sock include/net/sock.h:1459 [inline] #1: (sk_lock-AF_INET){+.+.}, at: [] tcp_sendpage+0x2e/0x60 net/ipv4/tcp.c:1069 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 663 Comm: khungtaskd Not tainted 4.13.0-rc6-next-20170825+ #9 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:16 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:52 nmi_cpu_backtrace+0x20e/0x240 lib/nmi_backtrace.c:102 nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:61 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 trigger_all_cpu_backtrace include/linux/nmi.h:105 [inline] check_hung_task kernel/hung_task.c:132 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline] watchdog+0x90c/0xd60 kernel/hung_task.c:249 kthread+0x39c/0x470 kernel/kthread.c:231 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431 Sending NMI from CPU 0 to CPUs 1-3: NMI backtrace for cpu 2 CPU: 2 PID: 2925 Comm: rs:main Q:Reg Not tainted 4.13.0-rc6-next-20170825+ #9 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff880068ffc340 task.stack: ffff8800697d0000 RIP: 0010:memcmp+0xcb/0x160 lib/string.c:859 RSP: 0018:ffff8800697d6ba0 EFLAGS: 00000246 RAX: 0000000000000000 RBX: ffff8800697d6ce0 RCX: 00000000000000ff RDX: ffff8800697d6ce0 RSI: ffff880068d165b0 RDI: 0000000000000007 RBP: ffff8800697d6bc8 R08: 0000000000000000 R09: 1ffff1000d2fad42 R10: 00000000db37e248 R11: 00000000bc08ac0a R12: dffffc0000000000 R13: 0000000000000098 R14: ffff880068d16500 R15: ffff8800697d6c48 FS: 00007f9212fab700(0000) GS:ffff88006de00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055d48e77de50 CR3: 0000000038f43000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: find_stack lib/stackdepot.c:176 [inline] depot_save_stack+0x12c/0x490 lib/stackdepot.c:225 save_stack+0xa3/0xd0 mm/kasan/kasan.c:453 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489 slab_post_alloc_hook mm/slab.h:444 [inline] slab_alloc mm/slab.c:3397 [inline] kmem_cache_alloc+0x11b/0x760 mm/slab.c:3559 kmem_cache_zalloc include/linux/slab.h:656 [inline] alloc_buffer_head+0x76/0x190 fs/buffer.c:3409 alloc_page_buffers+0xb7/0x200 fs/buffer.c:873 create_empty_buffers+0xd0/0x7b0 fs/buffer.c:1578 create_page_buffers+0x1ed/0x290 fs/buffer.c:1695 __block_write_begin_int+0x22c/0x1410 fs/buffer.c:2005 __block_write_begin+0x30/0x40 fs/buffer.c:2076 ext4_da_write_begin+0x4f1/0x1020 fs/ext4/inode.c:3080 generic_perform_write+0x28c/0x650 mm/filemap.c:2979 __generic_file_write_iter+0x366/0x5b0 mm/filemap.c:3104 ext4_file_write_iter+0x59e/0x10b0 fs/ext4/file.c:280 call_write_iter include/linux/fs.h:1744 [inline] new_sync_write fs/read_write.c:457 [inline] __vfs_write+0x68a/0x970 fs/read_write.c:470 vfs_write+0x18f/0x510 fs/read_write.c:518 SYSC_write fs/read_write.c:565 [inline] SyS_write+0xef/0x220 fs/read_write.c:557 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x7f9214a0919d RSP: 002b:00007f9212faa000 EFLAGS: 00000293 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00000000000003d2 RCX: 00007f9214a0919d RDX: 00000000000003d2 RSI: 00000000012ee340 RDI: 0000000000000006 RBP: 0000000000000086 R08: 0a3a332d31207355 R09: 676e69646e655320 R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001 R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000 Code: b6 03 48 c1 e9 03 83 e7 07 42 0f b6 0c 21 40 38 f9 7f 04 84 c9 75 7c 0f b6 0e 29 c8 75 0f 48 83 c3 01 48 83 c6 01 48 39 d3 75 b4 <31> c0 48 83 c4 18 5b 41 5c 5d c3 48 89 55 e0 48 89 75 e8 e8 ed NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff84da2b86 NMI backtrace for cpu 3 skipped: idling at pc 0xffffffff84da2b86