bisecting fixing commit since 3c8c23092588a23bf1856a64f58c37f477a413be building syzkaller on ed7d41c582d6f194ff35353d8bfdf7681dc0718e testing commit 3c8c23092588a23bf1856a64f58c37f477a413be with gcc (GCC) 8.4.1 20210217 kernel signature: 464ff470793eaf9dacf1763f0ca9fcb8897fed60eb23d0f03143c568f13ddcd8 all runs: crashed: INFO: task hung in n_tty_poll testing current HEAD 9a2dc0e6c531d595bcdf2c66d0be131679bd02df testing commit 9a2dc0e6c531d595bcdf2c66d0be131679bd02df with gcc (GCC) 8.4.1 20210217 kernel signature: 892ab3df4565c81dfba40a13970e0b4210c7101a3164437c7c8ed38241a60b6c all runs: crashed: INFO: task hung in n_tty_poll revisions tested: 2, total time: 32m15.158511523s (build: 19m36.982807561s, test: 12m11.400453915s) the crash still happens on HEAD commit msg: Linux 4.19.194 crash: INFO: task hung in n_tty_poll Bluetooth: hci3: command 0x0406 tx timeout Bluetooth: hci1: command 0x0406 tx timeout Bluetooth: hci5: command 0x0406 tx timeout ieee802154 phy0 wpan0: encryption failed: -22 ieee802154 phy1 wpan1: encryption failed: -22 INFO: task syz-executor.0:9947 blocked for more than 140 seconds. Not tainted 4.19.194-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D26984 9947 8479 0x00000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common+0x3fb/0x5d0 kernel/sched/completion.c:115 wait_for_completion+0x18/0x20 kernel/sched/completion.c:136 __flush_work+0x401/0x820 kernel/workqueue.c:2925 flush_work+0xb/0x10 kernel/workqueue.c:2946 tty_buffer_flush_work+0xd/0x10 drivers/tty/tty_buffer.c:613 n_tty_poll+0x450/0x820 drivers/tty/n_tty.c:2410 tty_poll+0x104/0x160 drivers/tty/tty_io.c:2110 vfs_poll include/linux/poll.h:90 [inline] do_select+0x8de/0x1190 fs/select.c:507 core_sys_select+0x414/0x6b0 fs/select.c:650 do_pselect fs/select.c:731 [inline] __do_sys_pselect6 fs/select.c:772 [inline] __se_sys_pselect6+0x3a1/0x420 fs/select.c:757 __x64_sys_pselect6+0xdc/0x1a0 fs/select.c:757 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4665d9 Code: Bad RIP value. RSP: 002b:00007fd588a73188 EFLAGS: 00000246 ORIG_RAX: 000000000000010e RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665d9 RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000040 RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000020000140 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007ffcd54d4a1f R14: 00007fd588a73300 R15: 0000000000022000 INFO: task syz-executor.4:9949 blocked for more than 140 seconds. Not tainted 4.19.194-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D27160 9949 8487 0x00000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common+0x3fb/0x5d0 kernel/sched/completion.c:115 wait_for_completion+0x18/0x20 kernel/sched/completion.c:136 __flush_work+0x401/0x820 kernel/workqueue.c:2925 flush_work+0xb/0x10 kernel/workqueue.c:2946 tty_buffer_flush_work+0xd/0x10 drivers/tty/tty_buffer.c:613 n_tty_poll+0x450/0x820 drivers/tty/n_tty.c:2410 tty_poll+0x104/0x160 drivers/tty/tty_io.c:2110 vfs_poll include/linux/poll.h:90 [inline] do_select+0x8de/0x1190 fs/select.c:507 core_sys_select+0x414/0x6b0 fs/select.c:650 do_pselect fs/select.c:731 [inline] __do_sys_pselect6 fs/select.c:772 [inline] __se_sys_pselect6+0x3a1/0x420 fs/select.c:757 __x64_sys_pselect6+0xdc/0x1a0 fs/select.c:757 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4665d9 Code: Bad RIP value. RSP: 002b:00007fd70cb27188 EFLAGS: 00000246 ORIG_RAX: 000000000000010e RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665d9 RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000040 RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000020000140 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007ffed4b1288f R14: 00007fd70cb27300 R15: 0000000000022000 INFO: task syz-executor.2:9974 blocked for more than 140 seconds. Not tainted 4.19.194-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D27880 9974 8478 0x00000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common+0x3fb/0x5d0 kernel/sched/completion.c:115 wait_for_completion+0x18/0x20 kernel/sched/completion.c:136 __flush_work+0x401/0x820 kernel/workqueue.c:2925 flush_work+0xb/0x10 kernel/workqueue.c:2946 tty_buffer_flush_work+0xd/0x10 drivers/tty/tty_buffer.c:613 n_tty_poll+0x450/0x820 drivers/tty/n_tty.c:2410 tty_poll+0x104/0x160 drivers/tty/tty_io.c:2110 vfs_poll include/linux/poll.h:90 [inline] do_select+0x8de/0x1190 fs/select.c:507 core_sys_select+0x414/0x6b0 fs/select.c:650 do_pselect fs/select.c:731 [inline] __do_sys_pselect6 fs/select.c:772 [inline] __se_sys_pselect6+0x3a1/0x420 fs/select.c:757 __x64_sys_pselect6+0xdc/0x1a0 fs/select.c:757 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4665d9 Code: Bad RIP value. RSP: 002b:00007f74441ba188 EFLAGS: 00000246 ORIG_RAX: 000000000000010e RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665d9 RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000040 RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000020000140 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007ffc572ed30f R14: 00007f74441ba300 R15: 0000000000022000 INFO: task syz-executor.1:9976 blocked for more than 140 seconds. Not tainted 4.19.194-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D27656 9976 8484 0x00000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common+0x3fb/0x5d0 kernel/sched/completion.c:115 wait_for_completion+0x18/0x20 kernel/sched/completion.c:136 __flush_work+0x401/0x820 kernel/workqueue.c:2925 flush_work+0xb/0x10 kernel/workqueue.c:2946 tty_buffer_flush_work+0xd/0x10 drivers/tty/tty_buffer.c:613 n_tty_poll+0x450/0x820 drivers/tty/n_tty.c:2410 tty_poll+0x104/0x160 drivers/tty/tty_io.c:2110 vfs_poll include/linux/poll.h:90 [inline] do_select+0x8de/0x1190 fs/select.c:507 core_sys_select+0x414/0x6b0 fs/select.c:650 do_pselect fs/select.c:731 [inline] __do_sys_pselect6 fs/select.c:772 [inline] __se_sys_pselect6+0x3a1/0x420 fs/select.c:757 __x64_sys_pselect6+0xdc/0x1a0 fs/select.c:757 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4665d9 Code: Bad RIP value. RSP: 002b:00007ff4e4d61188 EFLAGS: 00000246 ORIG_RAX: 000000000000010e RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665d9 RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000040 RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000020000140 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007fff2e76fccf R14: 00007ff4e4d61300 R15: 0000000000022000 INFO: task syz-executor.5:9988 blocked for more than 140 seconds. Not tainted 4.19.194-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D27768 9988 8486 0x00000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common+0x3fb/0x5d0 kernel/sched/completion.c:115 wait_for_completion+0x18/0x20 kernel/sched/completion.c:136 __flush_work+0x401/0x820 kernel/workqueue.c:2925 flush_work+0xb/0x10 kernel/workqueue.c:2946 tty_buffer_flush_work+0xd/0x10 drivers/tty/tty_buffer.c:613 n_tty_poll+0x450/0x820 drivers/tty/n_tty.c:2410 tty_poll+0x104/0x160 drivers/tty/tty_io.c:2110 vfs_poll include/linux/poll.h:90 [inline] do_select+0x8de/0x1190 fs/select.c:507 core_sys_select+0x414/0x6b0 fs/select.c:650 do_pselect fs/select.c:731 [inline] __do_sys_pselect6 fs/select.c:772 [inline] __se_sys_pselect6+0x3a1/0x420 fs/select.c:757 __x64_sys_pselect6+0xdc/0x1a0 fs/select.c:757 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4665d9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f1a6ef6b188 EFLAGS: 00000246 ORIG_RAX: 000000000000010e RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665d9 RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000040 RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000020000140 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007fffc890afbf R14: 00007f1a6ef6b300 R15: 0000000000022000 Showing all locks held in the system: 6 locks held by kworker/u4:0/7: 6 locks held by kworker/u4:2/104: 1 lock held by khungtaskd/1569: #0: 0000000085d15a24 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4443 6 locks held by kworker/u4:4/3488: 1 lock held by in:imklog/7845: #0: 000000000c710a27 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 5 locks held by kworker/u4:5/9212: 5 locks held by kworker/u4:6/9252: 1 lock held by syz-executor.0/9947: #0: 00000000ee41f862 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 1 lock held by syz-executor.4/9949: #0: 000000000e0b9b5a (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 1 lock held by syz-executor.2/9974: #0: 00000000f6619874 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 1 lock held by syz-executor.1/9976: #0: 00000000fcd48eac (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 1 lock held by syz-executor.3/9981: #0: 000000004ba38b72 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 6 locks held by kworker/u4:11/9984: 1 lock held by syz-executor.5/9988: #0: 000000008465a980 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1569 Comm: khungtaskd Not tainted 4.19.194-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x17c/0x226 lib/dump_stack.c:118 nmi_cpu_backtrace.cold.0+0x3c/0x78 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xf6/0x120 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline] watchdog+0x5c3/0xb40 kernel/hung_task.c:287 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 23 Comm: kworker/u4:1 Not tainted 4.19.194-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_nc_worker RIP: 0010:__lock_release kernel/locking/lockdep.c:3670 [inline] RIP: 0010:lock_release+0x23f/0x840 kernel/locking/lockdep.c:3927 Code: 48 c1 ea 03 0f b6 14 02 48 c7 c0 20 87 ad 8b 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 12 05 00 00 44 89 e8 0b 05 91 08 67 0a <0f> 84 cd 03 00 00 48 8d 4d 98 44 89 ea 4c 89 e6 4c 89 ff e8 39 54 RSP: 0018:ffff8880b5b97c60 EFLAGS: 00000006 RAX: 0000000000000003 RBX: 1ffff11016b72f8f RCX: ffffffff814c3e81 RDX: 0000000000000004 RSI: 0000000000000000 RDI: 0000000000000001 RBP: ffff8880b5b97d00 R08: 0000000000000000 R09: ffffed1017464552 R10: ffffed1017464552 R11: ffff8880ba322a93 R12: ffffffff8997e700 R13: 0000000000000003 R14: ffff8880b5b86e80 R15: ffff8880b5b86600 FS: 0000000000000000(0000) GS:ffff8880ba300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2e2bf0e010 CR3: 00000000a12e1000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: rcu_lock_release include/linux/rcupdate.h:247 [inline] rcu_read_unlock include/linux/rcupdate.h:681 [inline] batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:423 [inline] batadv_nc_worker+0x191/0x630 net/batman-adv/network-coding.c:730 process_one_work+0x7b9/0x15a0 kernel/workqueue.c:2152 worker_thread+0x85/0xb60 kernel/workqueue.c:2295 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415