bisecting fixing commit since ff33472c282e209da54cbc0c7c1c06ddfcc93d33 building syzkaller on c85e1c5be98819e885698b690ac15a8d05ae38a6 testing commit ff33472c282e209da54cbc0c7c1c06ddfcc93d33 with gcc (GCC) 8.1.0 kernel signature: a22b065859d6157dbab4a02545383304d1b1a22baad6bdaac89da9d7d83a4162 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 4520f06b03ae667e442da1ab9351fd28cd7ac598 testing commit 4520f06b03ae667e442da1ab9351fd28cd7ac598 with gcc (GCC) 8.1.0 kernel signature: 0b79a0250599d7264a7f8cf2eda5592bed99ab0b6e0678ed52bdb79a6b171381 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: OK run #7: OK run #8: OK run #9: OK revisions tested: 2, total time: 35m57.161853623s (build: 16m6.364252542s, test: 19m17.402243397s) the crash still happens on HEAD commit msg: Linux 4.14.175 crash: INFO: task hung in do_exit IPv6: ADDRCONF(NETDEV_UP): hsr0: link is not ready IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes ready IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready 8021q: adding VLAN 0 to HW filter on device batadv0 INFO: task syz-executor.4:8187 blocked for more than 140 seconds. Not tainted 4.14.175-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28264 8187 6251 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:00007ffdf0dc6b28 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 000000000000001e RCX: 0000000000459829 RDX: 0000000000413511 RSI: fffffffffffffff7 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffffffffffffffff R09: 00007ffdf0dc6b80 R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000001 R13: 00007ffdf0dc6b80 R14: 0000000000000000 R15: 00007ffdf0dc6b90 INFO: task syz-executor.4:8190 blocked for more than 140 seconds. Not tainted 4.14.175-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28848 8190 6251 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:00007fd7bdc88cf8 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: 00007ffdf0dc691f R14: 00007fd7bdc899c0 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 1 lock held by syz-executor.4/8187: #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.4/8190: #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 4.14.175-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: 8196 Comm: syz-executor.4 Not tainted 4.14.175-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8880a89f0180 task.stack: ffff888082430000 RIP: 0010:match_held_lock+0x2d0/0x740 kernel/locking/lockdep.c:3586 RSP: 0018:ffff8880824378c8 EFLAGS: 00000096 RAX: 0000000000000000 RBX: ffff8880a89f0a00 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff87990fa0 RDI: ffff8880a89f0a22 RBP: ffff8880824378e8 R08: ffffffff816b812c R09: 0000000000000000 R10: ffff888082437b88 R11: 0000000000000000 R12: 0000000000000000 R13: ffff8880a89f0a00 R14: ffffffff87990fa0 R15: ffff8880824378c0 FS: 00007fd7bdc68700(0000) GS:ffff8880aef00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005569f8deff68 CR3: 0000000092c03000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __lock_is_held+0xb5/0x140 kernel/locking/lockdep.c:3814 lock_is_held_type+0x118/0x210 kernel/locking/lockdep.c:4032 lock_is_held include/linux/lockdep.h:437 [inline] ___might_sleep+0x1fe/0x2a0 kernel/sched/core.c:6006 __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/0x1340 kernel/events/core.c:5414 call_mmap include/linux/fs.h:1783 [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:00007fd7bdc67c78 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: 00007fd7bdc686d4 R13: 00000000004c5d59 R14: 00000000004da6d0 R15: 00000000ffffffff Code: e8 36 de ff ff 45 31 e4 48 b8 00 00 00 00 00 fc ff df 48 01 c3 44 89 e0 48 c7 03 00 00 00 00 c7 43 08 00 00 00 00 48 83 c4 78 5b <41> 5c 41 5d 41 5e 41 5f 5d c3 41 bc 01 00 00 00 eb cb 48 8d 78