bisecting fixing commit since 6500aa436df40a46998f7a56a32e8199a3513e6d building syzkaller on 442206d76b974cca2d83ec763d4cf5ee829eb7d6 testing commit 6500aa436df40a46998f7a56a32e8199a3513e6d with gcc (GCC) 8.1.0 kernel signature: 70c02cb99b4cd7d9cfbf8138bba50515feaa61c2 all runs: crashed: INFO: task hung in do_exit testing current HEAD 174651bdf802a2139065e8e31ce950e2f3fc4a94 testing commit 174651bdf802a2139065e8e31ce950e2f3fc4a94 with gcc (GCC) 8.1.0 kernel signature: 0b3ed8311558c952599217ba287ae5db71835d12 all runs: crashed: INFO: task hung in do_exit revisions tested: 2, total time: 29m32.734315022s (build: 16m45.285252416s, test: 11m45.140402441s) the crash still happens on HEAD commit msg: Linux 4.19.87 crash: INFO: task hung in do_exit IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready 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.4:7095 blocked for more than 140 seconds. Not tainted 4.19.87-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28136 7095 6940 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+0x3b7/0x2d40 kernel/exit.c:863 do_group_exit+0xf4/0x2f0 kernel/exit.c:979 get_signal+0x313/0x1a00 kernel/signal.c:2578 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: 0033:0x45931a Code: Bad RIP value. RSP: 002b:00007ffd0bf80a88 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: fffffffffffffffc RBX: 0000000000000003 RCX: 000000000045931a 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.4:7096 blocked for more than 140 seconds. Not tainted 4.19.87-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28200 7096 6940 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+0x3b7/0x2d40 kernel/exit.c:863 do_group_exit+0xf4/0x2f0 kernel/exit.c:979 get_signal+0x313/0x1a00 kernel/signal.c:2578 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: 0033:0x4592c9 Code: Bad RIP value. RSP: 002b:00007fbb36c7ccf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 000000000075bf28 RCX: 00000000004592c9 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000075bf28 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000075bf2c R13: 00007ffd0bf80b2f R14: 00007fbb36c7d9c0 R15: 000000000075bf2c Showing all locks held in the system: 1 lock held by khungtaskd/1037: #0: 00000000b5f1c969 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4438 1 lock held by rsyslogd/6689: #0: 000000009611696d (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 2 locks held by getty/6811: #0: 000000007f34baca (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000eaff8628 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by getty/6812: #0: 00000000239f6f47 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000f6fdf005 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by getty/6813: #0: 00000000eb1908d5 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000bc2840af (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by getty/6814: #0: 000000000d89c624 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 0000000076891c99 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by getty/6815: #0: 00000000b36860f8 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 0000000010a1ca90 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by getty/6816: #0: 000000003c1f7b8a (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000dca9fb39 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by getty/6817: #0: 0000000097bff1d4 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000941fdc63 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 1 lock held by syz-executor.4/7095: #0: 00000000cf7921c6 (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000cf7921c6 (&mm->mmap_sem){++++}, at: do_exit+0x3b7/0x2d40 kernel/exit.c:863 1 lock held by syz-executor.4/7096: #0: 00000000cf7921c6 (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 00000000cf7921c6 (&mm->mmap_sem){++++}, at: do_exit+0x3b7/0x2d40 kernel/exit.c:863 1 lock held by syz-executor.4/7107: ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1037 Comm: khungtaskd Not tainted 4.19.87-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 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 7107 Comm: syz-executor.4 Not tainted 4.19.87-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__mutex_lock_common kernel/locking/mutex.c:925 [inline] RIP: 0010:__mutex_lock+0xe0/0x1210 kernel/locking/mutex.c:1072 Code: 04 25 28 00 00 00 48 89 45 c8 31 c0 e8 a9 4d c6 fa bf 01 00 00 00 e8 9f f2 c5 fa 49 8d 45 60 31 c9 31 d2 48 89 85 98 fe ff ff <48> 89 c7 4d 89 e1 89 de 41 57 41 b8 01 00 00 00 e8 db 46 cf fa 4c RSP: 0018:ffff888098fff900 EFLAGS: 00000246 RAX: ffff88809b6e58d0 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff87f99c60 RDI: ffff88809c3a5568 RBP: ffff888098fffa80 R08: ffffffff8175eccb R09: ffffed10136dcb0e R10: ffff888098fffa98 R11: ffff88809b6e5877 R12: 0000000000000000 R13: ffff88809b6e5870 R14: dffffc0000000000 R15: ffffffff8175eccb FS: 00007fbb36c5c700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f08f97bb140 CR3: 000000008b813000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 perf_mmap+0x65b/0x1660 kernel/events/core.c:5678 call_mmap include/linux/fs.h:1825 [inline] mmap_region+0x9b7/0x1470 mm/mmap.c:1763 do_mmap+0x6b5/0xea0 mm/mmap.c:1536 do_mmap_pgoff include/linux/mm.h:2314 [inline] vm_mmap_pgoff+0x195/0x210 mm/util.c:357 ksys_mmap_pgoff+0x3c6/0x650 mm/mmap.c:1586 __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: 0033:0x4592c9 Code: fd 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fbb36c5bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 00000000004592c9 RDX: 0000000000000000 RSI: 0000000000001000 RDI: 0000000020fff000 RBP: 000000000075bfc8 R08: 0000000000000003 R09: 0000000000000000 R10: 0000000000001011 R11: 0000000000000246 R12: 00007fbb36c5c6d4 R13: 00000000004c5625 R14: 00000000004d9a10 R15: 00000000ffffffff