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 1e986fe9ad15b8406034c504afc5ae76f0a8e852 testing commit 1e986fe9ad15b8406034c504afc5ae76f0a8e852 with gcc (GCC) 8.4.1 20210217 kernel signature: 24662b6f6731056d0a87fafa7ae8ee7ef43af449bf18edf379c246479cc29a81 all runs: crashed: INFO: task hung in do_exit revisions tested: 2, total time: 33m3.999975012s (build: 17m27.734131058s, test: 14m45.520837875s) the crash still happens on HEAD commit msg: Linux 4.19.191 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.4:6707 blocked for more than 140 seconds. Not tainted 4.19.191-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28168 6707 5651 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:799 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:00007ffd7ccee028 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: 00007ffd7ccee1f0 R13: 0000000000000006 R14: 0000000000000000 R15: 0000000000022000 INFO: task syz-executor.4:6708 blocked for more than 140 seconds. Not tainted 4.19.191-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28200 6708 5651 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:799 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:00007fcfaea9f218 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: 00007ffd7ccee09f R14: 00007fcfaea9f300 R15: 0000000000022000 Showing all locks held in the system: 1 lock held by khungtaskd/1047: #0: 0000000098fbef4f (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4443 1 lock held by in:imklog/5352: #0: 0000000048478b2e (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 1 lock held by syz-executor.4/6707: #0: 00000000b6f2486e (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000b6f2486e (&mm->mmap_sem){++++}, at: do_exit+0x5fc/0x2cf0 kernel/exit.c:857 1 lock held by syz-executor.4/6708: #0: 00000000b6f2486e (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000b6f2486e (&mm->mmap_sem){++++}, at: do_exit+0x5fc/0x2cf0 kernel/exit.c:857 2 locks held by syz-executor.4/6721: ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1047 Comm: khungtaskd Not tainted 4.19.191-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 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 6721 Comm: syz-executor.4 Not tainted 4.19.191-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:mark_lock+0x16/0x1340 kernel/locking/lockdep.c:3099 Code: 0f 0b e8 cd 26 45 00 eb d8 e8 e6 26 45 00 eb 87 0f 1f 40 00 55 4c 8d 46 20 89 d1 48 b8 00 00 00 00 00 fc ff df 48 89 e5 41 57 <49> 89 ff 41 56 41 89 d6 4c 89 c2 41 55 48 c1 ea 03 41 bd 01 00 00 RSP: 0018:ffff8881ddcbf668 EFLAGS: 00000046 RAX: dffffc0000000000 RBX: 00000000000006e8 RCX: 0000000000000002 RDX: 0000000000000002 RSI: ffff8881e452cb30 RDI: ffff8881e452c280 RBP: ffff8881ddcbf670 R08: ffff8881e452cb50 R09: 0000000000000001 R10: ffff8881e452cb30 R11: ffff8881e452caf4 R12: ffff8881e452cb52 R13: 0000000000000006 R14: ffff8881e452c280 R15: 0000000000000004 FS: 00007fcfaea7e700(0000) GS:ffff8881f6900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f23a9293028 CR3: 00000001df0ce002 CR4: 00000000001606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: mark_irqflags kernel/locking/lockdep.c:3024 [inline] __lock_acquire+0x6fb/0x4950 kernel/locking/lockdep.c:3373 lock_acquire+0x173/0x3d0 kernel/locking/lockdep.c:3908 __mutex_lock_common kernel/locking/mutex.c:928 [inline] __mutex_lock+0xf5/0x1200 kernel/locking/mutex.c:1075 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1090 perf_mmap+0x65b/0x1670 kernel/events/core.c:5689 call_mmap include/linux/fs.h:1826 [inline] mmap_region+0x9c0/0x14c0 mm/mmap.c:1757 do_mmap+0x6b5/0xe90 mm/mmap.c:1530 do_mmap_pgoff include/linux/mm.h:2326 [inline] vm_mmap_pgoff+0x195/0x210 mm/util.c:357 ksys_mmap_pgoff+0x3c6/0x650 mm/mmap.c:1580 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline] __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline] __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x461089 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fcfaea7e1a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: ffffffffffffffda RBX: 000000000052bfa8 RCX: 0000000000461089 RDX: 0000000000000000 RSI: 0000000000003000 RDI: 0000000020ffd000 RBP: 0000000000000006 R08: 0000000000000003 R09: 0000000000000000 R10: 0000000000001011 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000004f3488 R14: 00000000004b1b06 R15: 00007fcfaea7e6bc