bisecting fixing commit since 3c8c23092588a23bf1856a64f58c37f477a413be building syzkaller on ed7d41c582d6f194ff35353d8bfdf7681dc0718e testing commit 3c8c23092588a23bf1856a64f58c37f477a413be compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 2a3dcf84ec43ff80175a71b1dd832a39cadb541b867758f634d8f8df597d3e0e all runs: crashed: INFO: task hung in n_tty_poll testing current HEAD 5c66974a63046780925e5d99b6dc6631fe2f9a31 testing commit 5c66974a63046780925e5d99b6dc6631fe2f9a31 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 437c43edcfc812cda07d885661d1354ce2cd67ee1eb7b090db87c31bdcb4545b all runs: crashed: INFO: task hung in n_tty_poll revisions tested: 2, total time: 31m24.760538226s (build: 19m6.174068688s, test: 11m54.776787606s) the crash still happens on HEAD commit msg: Linux 4.19.202 crash: INFO: task hung in n_tty_poll Bluetooth: hci3: command 0x0406 tx timeout Bluetooth: hci1: command 0x0406 tx timeout Bluetooth: hci2: command 0x0406 tx timeout ieee802154 phy0 wpan0: encryption failed: -22 ieee802154 phy1 wpan1: encryption failed: -22 INFO: task syz-executor.3:9893 blocked for more than 140 seconds. Not tainted 4.19.202-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.3 D27496 9893 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:2926 flush_work+0xb/0x10 kernel/workqueue.c:2947 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:00007fca2fb50188 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: 00007ffe91a5baff R14: 00007fca2fb50300 R15: 0000000000022000 INFO: task syz-executor.1:9984 blocked for more than 140 seconds. Not tainted 4.19.202-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D27944 9984 8485 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:2926 flush_work+0xb/0x10 kernel/workqueue.c:2947 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:00007fe44474f188 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: 00007ffc83614ddf R14: 00007fe44474f300 R15: 0000000000022000 INFO: task syz-executor.5:9987 blocked for more than 140 seconds. Not tainted 4.19.202-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D27656 9987 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:2926 flush_work+0xb/0x10 kernel/workqueue.c:2947 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:00007fc57fe98188 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: 00007fff02950faf R14: 00007fc57fe98300 R15: 0000000000022000 INFO: task syz-executor.4:9996 blocked for more than 140 seconds. Not tainted 4.19.202-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D27480 9996 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:2926 flush_work+0xb/0x10 kernel/workqueue.c:2947 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:00007fdbe4883188 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: 00007ffd45b7e17f R14: 00007fdbe4883300 R15: 0000000000022000 Showing all locks held in the system: 5 locks held by kworker/u4:0/7: 6 locks held by kworker/u4:1/23: 6 locks held by kworker/u4:3/222: 6 locks held by kworker/u4:4/578: 1 lock held by khungtaskd/1566: #0: 000000004288897d (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4443 1 lock held by in:imklog/7794: #0: 0000000045d4f20e (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 6 locks held by kworker/u4:6/9830: 1 lock held by syz-executor.0/9888: #0: 0000000051261451 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 1 lock held by syz-executor.3/9893: #0: 000000002fd8dcac (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 1 lock held by syz-executor.2/9928: #0: 0000000043ad912e (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 6 locks held by kworker/u4:10/9953: 1 lock held by syz-executor.1/9984: #0: 00000000d715e4de (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 1 lock held by syz-executor.5/9987: #0: 0000000027cdb532 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 1 lock held by syz-executor.4/9996: #0: 000000005c8cb811 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1566 Comm: khungtaskd Not tainted 4.19.202-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: 4692 Comm: systemd-journal Not tainted 4.19.202-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__lock_release kernel/locking/lockdep.c:3705 [inline] RIP: 0010:lock_release+0x364/0x840 kernel/locking/lockdep.c:3927 Code: 00 00 fc ff df 48 c1 ee 03 80 3c 0e 00 0f 85 55 04 00 00 49 8d bf 78 08 00 00 4c 8b 20 48 b8 00 00 00 00 00 fc ff df 48 89 f9 <48> c1 e9 03 80 3c 01 00 0f 85 57 04 00 00 83 c2 01 4d 89 a7 78 08 RSP: 0018:ffff8880a130f620 EFLAGS: 00000046 RAX: dffffc0000000000 RBX: 1ffff11014261ec7 RCX: ffff8880a1304cb8 RDX: 0000000000000000 RSI: 1ffff11014260999 RDI: ffff8880a1304cb8 RBP: ffff8880a130f6c0 R08: 0000000000000000 R09: ffffed1017464552 R10: ffffed1017464552 R11: ffff8880ba322a93 R12: 0000000000000000 R13: 0000000000000001 R14: ffff8880a1304cc0 R15: ffff8880a1304440 FS: 00007f7d19f948c0(0000) GS:ffff8880ba300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f7d173d8000 CR3: 00000000a10d0000 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] is_bpf_text_address+0x7d/0xe0 kernel/bpf/core.c:547 kernel_text_address+0x79/0xf0 kernel/extable.c:152 __kernel_text_address+0xd/0x40 kernel/extable.c:107 unwind_get_return_address arch/x86/kernel/unwind_frame.c:18 [inline] unwind_get_return_address+0x58/0xa0 arch/x86/kernel/unwind_frame.c:13 __save_stack_trace+0x9c/0x100 arch/x86/kernel/stacktrace.c:45 save_stack_trace+0x1a/0x20 arch/x86/kernel/stacktrace.c:60 save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:553 kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:538 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490 slab_post_alloc_hook mm/slab.h:445 [inline] slab_alloc mm/slab.c:3397 [inline] kmem_cache_alloc+0x11b/0x390 mm/slab.c:3557 kmem_cache_zalloc include/linux/slab.h:699 [inline] __alloc_file+0x2b/0x2f0 fs/file_table.c:100 alloc_empty_file+0x45/0x110 fs/file_table.c:150 path_openat+0x107/0x2900 fs/namei.c:3526 do_filp_open+0x177/0x250 fs/namei.c:3567 do_sys_open+0x1dc/0x350 fs/open.c:1085 __do_sys_open fs/open.c:1103 [inline] __se_sys_open fs/open.c:1098 [inline] __x64_sys_open+0x79/0xb0 fs/open.c:1098 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f7d19523840 Code: 73 01 c3 48 8b 0d 68 77 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 89 bb 20 00 00 75 10 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 1e f6 ff ff 48 89 04 24 RSP: 002b:00007ffc4a838898 EFLAGS: 00000246 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: 00007ffc4a838ba0 RCX: 00007f7d19523840 RDX: 00000000000001a0 RSI: 0000000000080042 RDI: 000055e0c20fafd0 RBP: 000000000000000d R08: 000000000000c0ff R09: 00000000ffffffff R10: 0000000000000069 R11: 0000000000000246 R12: 00000000ffffffff R13: 000055e0c20ed040 R14: 00007ffc4a838b60 R15: 000055e0c20fb0c0