bisecting fixing commit since ff33472c282e209da54cbc0c7c1c06ddfcc93d33 building syzkaller on c85e1c5be98819e885698b690ac15a8d05ae38a6 testing commit ff33472c282e209da54cbc0c7c1c06ddfcc93d33 with gcc (GCC) 8.1.0 kernel signature: f1b533ec45c5b994c8412e29582bd6973d0706f0 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: crashed: INFO: task hung in do_exit run #5: crashed: INFO: task hung in do_exit run #6: crashed: INFO: task hung in do_exit run #7: OK run #8: OK run #9: OK testing current HEAD c04fc6fa5c96ec57316527b2228fa31f26494abe testing commit c04fc6fa5c96ec57316527b2228fa31f26494abe with gcc (GCC) 8.1.0 kernel signature: b9ef22d83af4d752682daee2fb63cfee5ef5f88e 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: OK run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK revisions tested: 2, total time: 37m10.047960237s (build: 16m10.784601642s, test: 20m25.371946377s) the crash still happens on HEAD commit msg: Linux 4.14.165 crash: INFO: task hung in do_exit INFO: task syz-executor.1:7808 blocked for more than 140 seconds. Not tainted 4.14.165-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D27904 7808 6977 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:00007ffe1ac0a248 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 000000000000001e RCX: 0000000000459829 RDX: 0000000000413511 RSI: fffffffffffffff7 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffffffffffffffff R09: 00007ffe1ac0a2a0 R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000001 R13: 00007ffe1ac0a2a0 R14: 0000000000000000 R15: 00007ffe1ac0a2b0 INFO: task syz-executor.1:7809 blocked for more than 140 seconds. Not tainted 4.14.165-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D28920 7809 6977 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:2413 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:00007f2512d61cf8 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: 00007ffe1ac0a03f R14: 00007f2512d629c0 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/6853: #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/6854: #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/6855: #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/6856: #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/6857: #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/6858: #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/6859: #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.1/7808: #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.1/7809: #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 4.14.165-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: 7817 Comm: syz-executor.1 Not tainted 4.14.165-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff88807bdf2240 task.stack: ffff8880989f8000 RIP: 0010:preempt_count_equals kernel/sched/core.c:5975 [inline] RIP: 0010:___might_sleep+0x80/0x2a0 kernel/sched/core.c:6008 RSP: 0018:ffff8880989ff978 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 1ffff1100f7be4b8 RSI: ffffffff87990fe0 RDI: ffff88807bdf25c0 RBP: ffff8880989ff9a0 R08: ffffffff816b6adc R09: 0000000000000000 R10: ffff8880989ffb88 R11: 0000000000000000 R12: 0000000000000000 R13: ffffffff868b1d40 R14: 00000000000002eb R15: ffff88807bdf2240 FS: 00007f2512d41700(0000) GS:ffff8880aef00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000001f1a4d0 CR3: 000000007e436000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __might_sleep+0x93/0xb0 kernel/sched/core.c:5994 __mutex_lock_common kernel/locking/mutex.c:747 [inline] __mutex_lock+0xc0/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 perf_mmap+0x4ac/0x1330 kernel/events/core.c:5411 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:00007f2512d40c78 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: 00007f2512d416d4 R13: 00000000004c5d59 R14: 00000000004da6d0 R15: 00000000ffffffff Code: 80 03 00 00 81 e3 ff ff ff 7f 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e e9 01 00 00 <41> 03 9f 80 03 00 00 41 39 dc 0f 84 d6 00 00 00 48 c7 c7 84 3a