bisecting fixing commit since cc4c818b2219c58af5f0ca59f3e9f02c48bc0b65 building syzkaller on cdde748628a830b9236db9890a9fea0764bde4fb testing commit cc4c818b2219c58af5f0ca59f3e9f02c48bc0b65 with gcc (GCC) 8.1.0 kernel signature: cf60e8ce71f204227c08e8a05906b86f1c16cab8caec338da946962c728c3a3e all runs: crashed: INFO: task hung in do_exit testing current HEAD 13d2ce42de8cb98ff952f8de6307f896203854c2 testing commit 13d2ce42de8cb98ff952f8de6307f896203854c2 with gcc (GCC) 8.1.0 kernel signature: cc9f2dd9b6279ae6767f594aab7aea5938d4ac8162e850de12f610312ced1970 all runs: crashed: INFO: task hung in do_exit revisions tested: 2, total time: 36m54.593220913s (build: 21m24.156319021s, test: 13m50.802265305s) the crash still happens on HEAD commit msg: Linux 4.19.163 crash: INFO: task hung in do_exit 8021q: adding VLAN 0 to HW filter on device batadv0 IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready 8021q: adding VLAN 0 to HW filter on device batadv0 8021q: adding VLAN 0 to HW filter on device batadv0 INFO: task syz-executor.0:6728 blocked for more than 140 seconds. Not tainted 4.19.163-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D28136 6728 5702 0x80000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x78c/0x1c10 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 __rwsem_down_read_failed_common kernel/locking/rwsem-xadd.c:292 [inline] rwsem_down_read_failed+0x21c/0x3e0 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:83 [inline] down_read+0x49/0xb0 kernel/locking/rwsem.c:26 exit_mm kernel/exit.c:512 [inline] do_exit+0x61f/0x2d70 kernel/exit.c:877 do_group_exit+0xf4/0x2f0 kernel/exit.c:993 get_signal+0x313/0x1a30 kernel/signal.c:2589 do_signal+0x87/0x1960 arch/x86/kernel/signal.c:821 exit_to_usermode_loop+0x114/0x200 arch/x86/entry/common.c:163 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x413/0x4e0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4598fa Code: Bad RIP value. RSP: 002b:00007ffd98a2d2b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: fffffffffffffffc RBX: 0000000000000003 RCX: 00000000004598fa RDX: 0000000000000003 RSI: 0000000000021000 RDI: 0000000000000000 RBP: ffffffffffffffff R08: ffffffffffffffff R09: 0000000000000000 R10: 0000000000020022 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000021000 R14: 0000000000020022 R15: 0000000000000000 INFO: task syz-executor.0:6730 blocked for more than 140 seconds. Not tainted 4.19.163-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D28200 6730 5702 0x80000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x78c/0x1c10 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 __rwsem_down_read_failed_common kernel/locking/rwsem-xadd.c:292 [inline] rwsem_down_read_failed+0x21c/0x3e0 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:83 [inline] down_read+0x49/0xb0 kernel/locking/rwsem.c:26 exit_mm kernel/exit.c:512 [inline] do_exit+0x61f/0x2d70 kernel/exit.c:877 do_group_exit+0xf4/0x2f0 kernel/exit.c:993 get_signal+0x313/0x1a30 kernel/signal.c:2589 do_signal+0x87/0x1960 arch/x86/kernel/signal.c:821 exit_to_usermode_loop+0x114/0x200 arch/x86/entry/common.c:163 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x413/0x4e0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4598a9 Code: Bad RIP value. RSP: 002b:00007f0744d10cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 000000000075bf28 RCX: 00000000004598a9 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000075bf28 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000075bf2c R13: 00007ffd98a2d35f R14: 00007f0744d119c0 R15: 000000000075bf2c Showing all locks held in the system: 1 lock held by khungtaskd/1044: #0: 00000000e80104e2 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4442 1 lock held by in:imklog/5338: #0: 00000000318ddd83 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 1 lock held by syz-executor.0/6728: #0: 00000000b82c7e4c (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000b82c7e4c (&mm->mmap_sem){++++}, at: do_exit+0x61f/0x2d70 kernel/exit.c:877 1 lock held by syz-executor.0/6730: #0: 00000000b82c7e4c (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000b82c7e4c (&mm->mmap_sem){++++}, at: do_exit+0x61f/0x2d70 kernel/exit.c:877 1 lock held by syz-executor.0/6745: ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1044 Comm: khungtaskd Not tainted 4.19.163-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+0x123/0x177 lib/dump_stack.c:118 nmi_cpu_backtrace.cold.4+0x3e/0x76 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xe6/0x11a 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: 23 Comm: kworker/u4:1 Not tainted 4.19.163-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_nc_worker RIP: 0010:trace_softirqs_on+0x197/0x3b0 kernel/locking/lockdep.c:2944 Code: 00 c7 83 70 08 00 00 01 00 00 00 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 09 02 00 00 48 8d bb 30 08 00 00 4c 89 ab 60 08 00 00 <48> b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 04 02 84 RSP: 0018:ffff8881f5027c28 EFLAGS: 00000046 RAX: dffffc0000000000 RBX: ffff8881f5014600 RCX: 0000000000000000 RDX: 1ffff1103ea029cc RSI: 0000000000000000 RDI: ffff8881f5014e30 RBP: ffff8881f5027c40 R08: 0000000000000001 R09: ffffed103ccdec55 R10: ffffed103ccdec55 R11: ffff8881e66f62ab R12: ffff8881f5014600 R13: ffffffff866db6b6 R14: 0000000000000000 R15: ffff8881d176e780 FS: 0000000000000000(0000) GS:ffff8881f6900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000560ae78f6140 CR3: 000000000806d001 CR4: 00000000001606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __local_bh_enable_ip+0x1d9/0x260 kernel/softirq.c:177 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:176 [inline] _raw_spin_unlock_bh+0x30/0x40 kernel/locking/spinlock.c:200 spin_unlock_bh include/linux/spinlock.h:374 [inline] batadv_nc_purge_paths+0x1d6/0x2f0 net/batman-adv/network-coding.c:482 batadv_nc_worker+0x225/0x630 net/batman-adv/network-coding.c:733 process_one_work+0x830/0x1670 kernel/workqueue.c:2155 worker_thread+0x85/0xb60 kernel/workqueue.c:2298 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415