bisecting fixing commit since ff33472c282e209da54cbc0c7c1c06ddfcc93d33 building syzkaller on c85e1c5be98819e885698b690ac15a8d05ae38a6 testing commit ff33472c282e209da54cbc0c7c1c06ddfcc93d33 with gcc (GCC) 8.1.0 kernel signature: ed52ed745a0f831ee8fefb8a95b8f3931b970feadf94c2d994b9180cde640a39 run #0: crashed: INFO: task hung in do_exit run #1: crashed: INFO: task hung in do_exit run #2: crashed: INFO: task hung in do_exit run #3: crashed: INFO: task hung in do_exit run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK testing current HEAD e0f8b8a65a473a8baa439cf865a694bbeb83fe90 testing commit e0f8b8a65a473a8baa439cf865a694bbeb83fe90 with gcc (GCC) 8.1.0 kernel signature: 470fa6180abac2205eab0c18463b57612d83d7bcab866c0a1129d58daf4d0562 run #0: crashed: INFO: task hung in do_exit run #1: crashed: INFO: task hung in do_exit run #2: crashed: INFO: task hung in do_exit run #3: crashed: INFO: task hung in do_exit run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK revisions tested: 2, total time: 36m32.563353119s (build: 16m16.861678384s, test: 19m40.815673647s) the crash still happens on HEAD commit msg: Linux 4.14.170 crash: INFO: task hung in do_exit INFO: task syz-executor.5:22111 blocked for more than 140 seconds. Not tainted 4.14.170-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D28264 22111 6871 0x80000000 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 __rwsem_down_read_failed_common kernel/locking/rwsem-xadd.c:292 [inline] rwsem_down_read_failed+0x1fc/0x390 kernel/locking/rwsem-xadd.c:309 call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94 __down_read arch/x86/include/asm/rwsem.h:66 [inline] down_read+0x49/0xb0 kernel/locking/rwsem.c:26 exit_mm kernel/exit.c:511 [inline] do_exit+0x558/0x2c00 kernel/exit.c:845 do_group_exit+0xf4/0x2f0 kernel/exit.c:955 SYSC_exit_group kernel/exit.c:966 [inline] SyS_exit_group+0x18/0x20 kernel/exit.c:964 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x459829 RSP: 002b:00007ffcd0236298 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 000000000000001e RCX: 0000000000459829 RDX: 0000000000413511 RSI: fffffffffffffff7 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffffffffffffffff R09: 00007ffcd02362f0 R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000001 R13: 00007ffcd02362f0 R14: 0000000000000000 R15: 00007ffcd0236300 INFO: task syz-executor.5:22120 blocked for more than 140 seconds. Not tainted 4.14.170-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D28920 22120 6871 0x80000000 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 __rwsem_down_read_failed_common kernel/locking/rwsem-xadd.c:292 [inline] rwsem_down_read_failed+0x1fc/0x390 kernel/locking/rwsem-xadd.c:309 call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94 __down_read arch/x86/include/asm/rwsem.h:66 [inline] down_read+0x49/0xb0 kernel/locking/rwsem.c:26 exit_mm kernel/exit.c:511 [inline] do_exit+0x558/0x2c00 kernel/exit.c:845 do_group_exit+0xf4/0x2f0 kernel/exit.c:955 get_signal+0x2fe/0x1b30 kernel/signal.c:2418 do_signal+0x7f/0x19a0 arch/x86/kernel/signal.c:814 exit_to_usermode_loop+0x114/0x1b0 arch/x86/entry/common.c:160 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline] syscall_return_slowpath arch/x86/entry/common.c:270 [inline] do_syscall_64+0x416/0x5b0 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x459829 RSP: 002b:00007f60193dfcf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 000000000075bf28 RCX: 0000000000459829 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000075bf28 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000075bf2c R13: 00007ffcd023608f R14: 00007f60193e09c0 R15: 000000000075bf2c Showing all locks held in the system: 1 lock held by khungtaskd/1016: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4544 2 locks held by getty/6749: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6750: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6751: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6752: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6753: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6754: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6755: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 1 lock held by syz-executor.5/22111: #0: (&mm->mmap_sem){++++}, at: [] exit_mm kernel/exit.c:511 [inline] #0: (&mm->mmap_sem){++++}, at: [] do_exit+0x558/0x2c00 kernel/exit.c:845 1 lock held by syz-executor.5/22120: #0: (&mm->mmap_sem){++++}, at: [] exit_mm kernel/exit.c:511 [inline] #0: (&mm->mmap_sem){++++}, at: [] do_exit+0x558/0x2c00 kernel/exit.c:845 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1016 Comm: khungtaskd Not tainted 4.14.170-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xf7/0x13b lib/dump_stack.c:58 nmi_cpu_backtrace.cold.4+0x3e/0x76 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xe5/0x119 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:140 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline] watchdog+0x522/0xb40 kernel/hung_task.c:274 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 22125 Comm: syz-executor.5 Not tainted 4.14.170-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff88808f99e240 task.stack: ffff888097048000 RIP: 0010:debug_lockdep_rcu_enabled.part.3+0x3b/0x60 kernel/rcu/update.c:299 RSP: 0018:ffff88809704f9f8 EFLAGS: 00000046 RAX: 0000000000000007 RBX: ffff88808f99e240 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff88808f99eabc RBP: ffff88809704fa00 R08: ffff88808f99eb08 R09: 0000000000000000 R10: ffff88809704fb88 R11: ffff8880a8529800 R12: ffff88808f99e240 R13: ffff88809ba16c00 R14: ffffed1013742d85 R15: ffff88809ba16ba0 FS: 00007f60193bf700(0000) GS:ffff8880aef00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f7d8fd17140 CR3: 000000009e8e6000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: debug_lockdep_rcu_enabled+0x77/0x90 kernel/rcu/update.c:299 trace_lock_release include/trace/events/lock.h:58 [inline] lock_release+0x5e3/0x830 kernel/locking/lockdep.c:4012 __mutex_unlock_slowpath+0x7d/0x7e0 kernel/locking/mutex.c:1018 mutex_unlock+0xd/0x10 kernel/locking/mutex.c:614 perf_mmap+0x5a3/0x1330 kernel/events/core.c:5427 call_mmap include/linux/fs.h:1782 [inline] mmap_region+0x7a2/0xf90 mm/mmap.c:1717 do_mmap+0x544/0xe20 mm/mmap.c:1495 do_mmap_pgoff include/linux/mm.h:2173 [inline] vm_mmap_pgoff+0x181/0x200 mm/util.c:333 SYSC_mmap_pgoff mm/mmap.c:1545 [inline] SyS_mmap_pgoff+0x3ca/0x6b0 mm/mmap.c:1503 SYSC_mmap arch/x86/kernel/sys_x86_64.c:100 [inline] SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:91 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x459829 RSP: 002b:00007f60193bec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 0000000000459829 RDX: 0000000003000001 RSI: 0000000000003000 RDI: 0000000020ffd000 RBP: 000000000075bfc8 R08: 0000000000000003 R09: 0000000000000000 R10: 0000000000001011 R11: 0000000000000246 R12: 00007f60193bf6d4 R13: 00000000004c5d59 R14: 00000000004da6d0 R15: 00000000ffffffff Code: 48 8b 1c 25 40 ee 01 00 48 8d bb 7c 08 00 00 48 89 fa 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 10 <8b> 93 7c 08 00 00 31 c0 5b 5d 85 d2 0f 94 c0 c3 e8 d0 c1 37 00