bisecting fixing commit since cc4c818b2219c58af5f0ca59f3e9f02c48bc0b65 building syzkaller on cdde748628a830b9236db9890a9fea0764bde4fb testing commit cc4c818b2219c58af5f0ca59f3e9f02c48bc0b65 with gcc (GCC) 8.1.0 kernel signature: b909597c4de70d666e99dee72c980872be392f571c5ed1b14711ad75158dcf8d all runs: crashed: INFO: task hung in do_exit testing current HEAD a87f96283793d58b042618c689630db264715274 testing commit a87f96283793d58b042618c689630db264715274 with gcc (GCC) 8.1.0 kernel signature: 9f381578d7f7a0e62bf010d9586b02e4522a13c156577d1a14adcda1509af627 all runs: crashed: INFO: task hung in do_exit revisions tested: 2, total time: 29m41.108233773s (build: 16m17.353763272s, test: 12m36.262024333s) the crash still happens on HEAD commit msg: Linux 4.19.145 crash: INFO: task hung in do_exit 8021q: adding VLAN 0 to HW filter on device batadv0 INFO: task syz-executor.4:14996 blocked for more than 140 seconds. Not tainted 4.19.145-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28136 14996 6359 0x80000000 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/0x2d20 kernel/exit.c:874 do_group_exit+0xf4/0x2f0 kernel/exit.c:990 __do_sys_exit_group kernel/exit.c:1001 [inline] __se_sys_exit_group kernel/exit.c:999 [inline] __x64_sys_exit_group+0x39/0x40 kernel/exit.c:999 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4598a9 Code: Bad RIP value. RSP: 002b:00007ffdf56854c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 000000000000001e RCX: 00000000004598a9 RDX: 0000000000413511 RSI: fffffffffffffff7 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffffffffffffffff R09: 00007ffdf5685520 R10: 00000000007613b0 R11: 0000000000000246 R12: 0000000000000001 R13: 00007ffdf5685520 R14: 0000000000000000 R15: 00007ffdf5685530 INFO: task syz-executor.4:15000 blocked for more than 140 seconds. Not tainted 4.19.145-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D27720 15000 6359 0x80000002 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/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:00007f7f805ffc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00000000004598a9 RDX: 0000000000000004 RSI: 0000000000002405 RDI: 0000000000000003 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f7f806006d4 R13: 00000000004cd3c0 R14: 00000000004d69e8 R15: 00000000ffffffff Showing all locks held in the system: 1 lock held by khungtaskd/1043: #0: 00000000ba94bdd6 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4442 1 lock held by in:imklog/5915: #0: 00000000c8183ef9 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 1 lock held by syz-executor.4/14996: #0: 00000000857c8c60 (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000857c8c60 (&mm->mmap_sem){++++}, at: do_exit+0x61f/0x2d20 kernel/exit.c:874 1 lock held by syz-executor.4/15000: #0: 00000000857c8c60 (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000857c8c60 (&mm->mmap_sem){++++}, at: do_exit+0x61f/0x2d20 kernel/exit.c:874 1 lock held by syz-executor.4/15007: ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1043 Comm: khungtaskd Not tainted 4.19.145-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: 15007 Comm: syz-executor.4 Not tainted 4.19.145-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:lock_acquire+0x23/0x3d0 kernel/locking/lockdep.c:3896 Code: 1f 84 00 00 00 00 00 48 b8 00 00 00 00 00 fc ff df 55 48 89 e5 41 57 4d 89 cf 41 56 45 89 c6 41 55 41 89 cd 41 54 41 89 d4 53 <89> f3 48 83 ec 20 48 89 7d d0 65 48 8b 14 25 40 ee 01 00 48 8d ba RSP: 0018:ffff88808dc2f8c0 EFLAGS: 00000246 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88808df06610 RBP: ffff88808dc2f8e8 R08: 0000000000000001 R09: 0000000000000000 R10: ffff88808dc2fa98 R11: ffff88808df065b7 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000 FS: 00007f7f805df700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000da6978 CR3: 0000000094a24000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf5/0x1210 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 perf_mmap+0x65b/0x1670 kernel/events/core.c:5687 call_mmap include/linux/fs.h:1826 [inline] mmap_region+0x9b7/0x1470 mm/mmap.c:1757 do_mmap+0x6b5/0xea0 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: 0033:0x4598a9 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:00007f7f805dec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 00000000004598a9 RDX: 0000000000000000 RSI: 0000000000003000 RDI: 0000000020ffd000 RBP: 000000000075bfc8 R08: 0000000000000003 R09: 0000000000000000 R10: 0000000000001011 R11: 0000000000000246 R12: 00007f7f805df6d4 R13: 00000000004c5df1 R14: 00000000004da7c8 R15: 00000000ffffffff