bisecting fixing commit since cc4c818b2219c58af5f0ca59f3e9f02c48bc0b65 building syzkaller on cdde748628a830b9236db9890a9fea0764bde4fb testing commit cc4c818b2219c58af5f0ca59f3e9f02c48bc0b65 with gcc (GCC) 8.1.0 kernel signature: 470fa028227e52347f6a48630743d17ac33a161796145cb7e9173b3065e2de40 all runs: crashed: INFO: task hung in do_exit testing current HEAD 17a87580a8856170d59aab302226811a4ae69149 testing commit 17a87580a8856170d59aab302226811a4ae69149 with gcc (GCC) 8.1.0 kernel signature: 4f0af1c64844f1434cea422270642896a9f16cf15193595b5e43cc34c6c8fa9c all runs: crashed: INFO: task hung in do_exit revisions tested: 2, total time: 31m15.836836218s (build: 18m14.24324784s, test: 11m54.206371632s) the crash still happens on HEAD commit msg: Linux 4.19.133 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.2:7448 blocked for more than 140 seconds. Not tainted 4.19.133-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D27688 7448 6389 0x80000004 Call Trace: context_switch kernel/sched/core.c:2826 [inline] __schedule+0x78c/0x1c10 kernel/sched/core.c:3515 schedule+0x7f/0x1b0 kernel/sched/core.c:3559 __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/0x2d20 kernel/exit.c:874 do_group_exit+0xf4/0x2f0 kernel/exit.c:990 get_signal+0x313/0x1a30 kernel/signal.c:2588 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:00007fffdf8eef38 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.2:7454 blocked for more than 140 seconds. Not tainted 4.19.133-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D28200 7454 6389 0x80000004 Call Trace: context_switch kernel/sched/core.c:2826 [inline] __schedule+0x78c/0x1c10 kernel/sched/core.c:3515 schedule+0x7f/0x1b0 kernel/sched/core.c:3559 __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/0x2d20 kernel/exit.c:874 do_group_exit+0xf4/0x2f0 kernel/exit.c:990 get_signal+0x313/0x1a30 kernel/signal.c:2588 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:00007feae14cecf8 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: 00007fffdf8eefdf R14: 00007feae14cf9c0 R15: 000000000075bf2c INFO: task syz-executor.4:7493 blocked for more than 140 seconds. Not tainted 4.19.133-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28136 7493 6398 0x80000004 Call Trace: context_switch kernel/sched/core.c:2826 [inline] __schedule+0x78c/0x1c10 kernel/sched/core.c:3515 schedule+0x7f/0x1b0 kernel/sched/core.c:3559 __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/0x2d20 kernel/exit.c:874 do_group_exit+0xf4/0x2f0 kernel/exit.c:990 get_signal+0x313/0x1a30 kernel/signal.c:2588 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:00007ffe6f34aaf8 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.4:7495 blocked for more than 140 seconds. Not tainted 4.19.133-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28200 7495 6398 0x80000004 Call Trace: context_switch kernel/sched/core.c:2826 [inline] __schedule+0x78c/0x1c10 kernel/sched/core.c:3515 schedule+0x7f/0x1b0 kernel/sched/core.c:3559 __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/0x2d20 kernel/exit.c:874 do_group_exit+0xf4/0x2f0 kernel/exit.c:990 get_signal+0x313/0x1a30 kernel/signal.c:2588 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: 7d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 4b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffa7bd15cf8 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: 00007ffe6f34ab9f R14: 00007ffa7bd169c0 R15: 000000000075bf2c Showing all locks held in the system: 1 lock held by khungtaskd/1041: #0: 00000000282ae066 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4442 1 lock held by in:imklog/5878: #0: 00000000ad1e2e01 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 1 lock held by syz-executor.2/7448: #0: 0000000010486bbd (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 0000000010486bbd (&mm->mmap_sem){++++}, at: do_exit+0x61f/0x2d20 kernel/exit.c:874 1 lock held by syz-executor.2/7454: #0: 0000000010486bbd (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 0000000010486bbd (&mm->mmap_sem){++++}, at: do_exit+0x61f/0x2d20 kernel/exit.c:874 2 locks held by syz-executor.2/7459: 1 lock held by syz-executor.4/7493: #0: 00000000e6671460 (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000e6671460 (&mm->mmap_sem){++++}, at: do_exit+0x61f/0x2d20 kernel/exit.c:874 1 lock held by syz-executor.4/7495: #0: 00000000e6671460 (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000e6671460 (&mm->mmap_sem){++++}, at: do_exit+0x61f/0x2d20 kernel/exit.c:874 1 lock held by syz-executor.4/7501: ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1041 Comm: khungtaskd Not tainted 4.19.133-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+0x324/0x3e0 kernel/kthread.c:246 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: 10 Comm: rcu_preempt Not tainted 4.19.133-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:mark_lock+0xb7/0x1340 kernel/locking/lockdep.c:3106 Code: d4 7a 89 49 8d 7c 24 30 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 aa 0e 00 00 4d 85 6c 24 30 74 5f <41> bd 01 00 00 00 48 83 c4 20 44 89 e8 5b 41 5c 41 5d 41 5e 41 5f RSP: 0018:ffff8880aa3777c8 EFLAGS: 00000006 RAX: dffffc0000000000 RBX: ffff8880aa364b08 RCX: 1ffff1101546c965 RDX: 1ffffffff12f5a9e RSI: ffff8880aa364b08 RDI: ffffffff897ad4f0 RBP: ffff8880aa377810 R08: ffff8880aa364b28 R09: 0000000000000000 R10: ffff8880aa364b08 R11: ffff8880aa364af4 R12: ffffffff897ad4c0 R13: 0000000000000100 R14: 0000000000000008 R15: ffff8880aa364280 FS: 0000000000000000(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f768ff35020 CR3: 0000000092868000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __lock_acquire+0x792/0x4980 kernel/locking/lockdep.c:3376 lock_acquire+0x173/0x3d0 kernel/locking/lockdep.c:3907 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152 debug_object_assert_init+0xec/0x370 lib/debugobjects.c:676 debug_timer_assert_init kernel/time/timer.c:724 [inline] debug_assert_init kernel/time/timer.c:776 [inline] try_to_del_timer_sync+0x68/0x100 kernel/time/timer.c:1223 del_timer_sync+0x156/0x1e0 kernel/time/timer.c:1293 schedule_timeout+0x3b3/0xda0 kernel/time/timer.c:1807 rcu_gp_kthread+0xce6/0x23d0 kernel/rcu/tree.c:2202 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415