bisecting fixing commit since cc4c818b2219c58af5f0ca59f3e9f02c48bc0b65 building syzkaller on cdde748628a830b9236db9890a9fea0764bde4fb testing commit cc4c818b2219c58af5f0ca59f3e9f02c48bc0b65 with gcc (GCC) 8.4.1 20210217 kernel signature: a1bb834164b2d6b522303c38486ae327d635f78bcc25d23d49bb16afffeb9d40 all runs: crashed: INFO: task hung in do_exit testing current HEAD 255b58a2b3af0baa0ee11507390349217b8b73b0 testing commit 255b58a2b3af0baa0ee11507390349217b8b73b0 with gcc (GCC) 8.4.1 20210217 kernel signature: 3ca57a32ad3fed69f65eabd60515123ce7d964fdcc364aa160f8a7b95086f3f3 all runs: crashed: INFO: task hung in do_exit revisions tested: 2, total time: 30m7.494387148s (build: 15m2.643233505s, test: 14m7.518535754s) the crash still happens on HEAD commit msg: Linux 4.19.176 crash: INFO: task hung in do_exit IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes ready 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 INFO: task syz-executor.4:6607 blocked for more than 140 seconds. Not tainted 4.19.176-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28168 6607 5678 0x80000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0xdb5/0x1d40 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+0x5fc/0x2cf0 kernel/exit.c:857 do_group_exit+0xf4/0x2f0 kernel/exit.c:967 get_signal+0x316/0x19e0 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: 0033:0x4610d2 Code: Bad RIP value. RSP: 002b:00007ffecd11ed98 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: fffffffffffffffc RBX: 0000000000020022 RCX: 00000000004610d2 RDX: 0000000000000000 RSI: 0000000000021000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 00000000ffffffff R09: 0000000000000000 R10: 0000000000020022 R11: 0000000000000246 R12: 00007ffecd11ef60 R13: 0000000000000006 R14: 0000000000000000 R15: 0000000000022000 INFO: task syz-executor.4:6608 blocked for more than 140 seconds. Not tainted 4.19.176-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28200 6608 5678 0x80000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0xdb5/0x1d40 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+0x5fc/0x2cf0 kernel/exit.c:857 do_group_exit+0xf4/0x2f0 kernel/exit.c:967 get_signal+0x316/0x19e0 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: 0033:0x461089 Code: Bad RIP value. RSP: 002b:00007f0b99570218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 000000000052bf08 RCX: 0000000000461089 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000052bf08 RBP: 000000000052bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000052bf0c R13: 00007ffecd11ee0f R14: 00007f0b99570300 R15: 0000000000022000 INFO: task syz-executor.0:6615 blocked for more than 140 seconds. Not tainted 4.19.176-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D28168 6615 5683 0x80000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0xdb5/0x1d40 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+0x5fc/0x2cf0 kernel/exit.c:857 do_group_exit+0xf4/0x2f0 kernel/exit.c:967 get_signal+0x316/0x19e0 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: 0033:0x4610d2 Code: Bad RIP value. RSP: 002b:00007fff6b61d748 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: fffffffffffffffc RBX: 0000000000020022 RCX: 00000000004610d2 RDX: 0000000000000000 RSI: 0000000000021000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 00000000ffffffff R09: 0000000000000000 R10: 0000000000020022 R11: 0000000000000246 R12: 00007fff6b61d910 R13: 0000000000000006 R14: 0000000000000000 R15: 0000000000022000 INFO: task syz-executor.0:6617 blocked for more than 140 seconds. Not tainted 4.19.176-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D28200 6617 5683 0x80000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0xdb5/0x1d40 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+0x5fc/0x2cf0 kernel/exit.c:857 do_group_exit+0xf4/0x2f0 kernel/exit.c:967 get_signal+0x316/0x19e0 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: 0033:0x461089 Code: Bad RIP value. RSP: 002b:00007fb39140d218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 000000000052bf08 RCX: 0000000000461089 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000052bf08 RBP: 000000000052bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000052bf0c R13: 00007fff6b61d7bf R14: 00007fb39140d300 R15: 0000000000022000 Showing all locks held in the system: 1 lock held by khungtaskd/1044: #0: 00000000f6dc2aff (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4442 1 lock held by in:imklog/5338: #0: 000000009d02c582 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 1 lock held by syz-executor.4/6607: #0: 00000000d4dde5e1 (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000d4dde5e1 (&mm->mmap_sem){++++}, at: do_exit+0x5fc/0x2cf0 kernel/exit.c:857 1 lock held by syz-executor.4/6608: #0: 00000000d4dde5e1 (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000d4dde5e1 (&mm->mmap_sem){++++}, at: do_exit+0x5fc/0x2cf0 kernel/exit.c:857 1 lock held by syz-executor.4/6611: 1 lock held by syz-executor.0/6615: #0: 00000000492927ff (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000492927ff (&mm->mmap_sem){++++}, at: do_exit+0x5fc/0x2cf0 kernel/exit.c:857 1 lock held by syz-executor.0/6617: #0: 00000000492927ff (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000492927ff (&mm->mmap_sem){++++}, at: do_exit+0x5fc/0x2cf0 kernel/exit.c:857 1 lock held by syz-executor.0/6621: ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1044 Comm: khungtaskd Not tainted 4.19.176-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+0x123/0x171 lib/dump_stack.c:118 nmi_cpu_backtrace.cold.4+0x3e/0x76 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xe6/0x120 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 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 31 Comm: kworker/u4:2 Not tainted 4.19.176-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_nc_worker RIP: 0010:debug_lockdep_rcu_enabled.part.3+0x3b/0x60 kernel/rcu/update.c:253 Code: 8b 1c 25 40 ee 01 00 48 8d bb 84 08 00 00 48 89 fa 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 10 <8b> 93 84 08 00 00 31 c0 5b 5d 85 d2 0f 94 c0 c3 e8 20 0f 40 00 eb RSP: 0018:ffff8881f50cfce0 EFLAGS: 00000246 RAX: 0000000000000007 RBX: ffff8881f50c2100 RCX: 1ffff1103ea1853f RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8881f50c2984 RBP: ffff8881f50cfce8 R08: ffff8881f50c29f8 R09: 0000000000000002 R10: ffff8881f50c29d8 R11: 0000000000000001 R12: ffff8881ea07c440 R13: 00000000000002b3 R14: ffff8881e9957258 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8881f6800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f22c6a9d000 CR3: 000000000806d004 CR4: 00000000001606f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: debug_lockdep_rcu_enabled+0x77/0x90 kernel/rcu/update.c:253 rcu_read_lock include/linux/rcupdate.h:628 [inline] batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:419 [inline] batadv_nc_worker+0xf1/0x630 net/batman-adv/network-coding.c:730 process_one_work+0x830/0x1670 kernel/workqueue.c:2152 worker_thread+0x85/0xb60 kernel/workqueue.c:2295 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415