bisecting fixing commit since ff33472c282e209da54cbc0c7c1c06ddfcc93d33 building syzkaller on c85e1c5be98819e885698b690ac15a8d05ae38a6 testing commit ff33472c282e209da54cbc0c7c1c06ddfcc93d33 with gcc (GCC) 8.1.0 kernel signature: d94e59b5094e3c4544fbdfe0aed94ac61e76a7d69ea6e6fa63e4b05ebb66efb3 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: crashed: INFO: task hung in do_exit run #8: OK run #9: OK testing current HEAD 773e2b1cd56a17bab4cdd4fe7db12f2140951668 testing commit 773e2b1cd56a17bab4cdd4fe7db12f2140951668 with gcc (GCC) 8.1.0 kernel signature: 850e79c3abb4f1a64355754ebff757b629b5d4c76c498af6426cf4ee4decc626 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: crashed: INFO: task hung in do_exit run #8: OK run #9: OK revisions tested: 2, total time: 36m49.794779453s (build: 16m39.029396674s, test: 19m16.058075162s) the crash still happens on HEAD commit msg: Linux 4.14.178 crash: INFO: task hung in do_exit INFO: task syz-executor.0:15818 blocked for more than 140 seconds. Not tainted 4.14.178-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D28264 15818 6245 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:00007fffe39030b8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 000000000000001e RCX: 0000000000459829 RDX: 0000000000413511 RSI: fffffffffffffff7 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffffffffffffffff R09: 00007fffe3903110 R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000001 R13: 00007fffe3903110 R14: 0000000000000000 R15: 00007fffe3903120 INFO: task syz-executor.0:15820 blocked for more than 140 seconds. Not tainted 4.14.178-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D28920 15820 6245 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:2423 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:00007f7ae25eacf8 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: 00007fffe3902eaf R14: 00007f7ae25eb9c0 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:4548 1 lock held by syz-executor.0/15818: #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.0/15820: #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 4.14.178-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: 22 Comm: kworker/u4:1 Not tainted 4.14.178-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_nc_worker task: ffff8880a9e405c0 task.stack: ffff8880a9e48000 RIP: 0010:__lock_release kernel/locking/lockdep.c:3767 [inline] RIP: 0010:lock_release+0x246/0x830 kernel/locking/lockdep.c:4017 RSP: 0018:ffff8880a9e4fbc8 EFLAGS: 00000006 RAX: 0000000000000003 RBX: 1ffff110153c9f7d RCX: ffff8880a9e40e48 RDX: 0000000000000004 RSI: 0000000000000001 RDI: ffffffff87cb5040 RBP: ffff8880a9e4fc70 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000050 R11: ffff8880a9e405c0 R12: ffffffff893867c0 R13: ffff888093091380 R14: 0000000000000003 R15: ffff8880a9e405c0 FS: 0000000000000000(0000) GS:ffff8880aef00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f13b085f000 CR3: 0000000094a41000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:174 [inline] _raw_spin_unlock_bh+0x1a/0x40 kernel/locking/spinlock.c:208 spin_unlock_bh include/linux/spinlock.h:362 [inline] batadv_nc_purge_paths+0x1d6/0x2f0 net/batman-adv/network-coding.c:479 batadv_nc_worker+0x1f6/0x630 net/batman-adv/network-coding.c:727 process_one_work+0x79e/0x16c0 kernel/workqueue.c:2116 worker_thread+0xcc/0xee0 kernel/workqueue.c:2250 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Code: c1 ea 03 0f b6 14 02 4c 89 e0 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 48 05 00 00 44 89 f0 0b 05 b0 fd f0 07 0f 84 51 04 00 00 <48> 8d 4d 98 44 89 f2 4c 89 ee 4c 89 ff e8 c8 39 ff ff 48 85 c0