bisecting fixing commit since c98875d930e915d01e8c40c7d3c16f00b3c8abe1 building syzkaller on b0e8efcb4b0aac61f4647a76bbe54a5d38a370ba testing commit c98875d930e915d01e8c40c7d3c16f00b3c8abe1 with gcc (GCC) 8.1.0 kernel signature: 22e766d884759c2735b6f6e883420cf1d24b31d43f0ba87c8665fe1ff0640f6e all runs: crashed: INFO: task hung in p9_fd_close testing current HEAD dce0f88600e49746b4bda873965b671a23ff4313 testing commit dce0f88600e49746b4bda873965b671a23ff4313 with gcc (GCC) 8.1.0 kernel signature: 9bc4d6d76901989287dd396e17bf1d2076f526d5f84100ed0c30b404533cef1a all runs: crashed: INFO: task hung in p9_fd_close revisions tested: 2, total time: 29m48.244318675s (build: 17m41.619025639s, test: 11m22.162544908s) the crash still happens on HEAD commit msg: Linux 4.19.132 crash: INFO: task hung in p9_fd_close 8021q: adding VLAN 0 to HW filter on device batadv0 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.4:7878 blocked for more than 140 seconds. Not tainted 4.19.132-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D27912 7878 6235 0x00000004 Call Trace: context_switch kernel/sched/core.c:2826 [inline] __schedule+0x792/0x1c20 kernel/sched/core.c:3515 schedule+0x7f/0x1b0 kernel/sched/core.c:3559 schedule_timeout+0x6d7/0xda0 kernel/time/timer.c:1782 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common kernel/sched/completion.c:115 [inline] wait_for_completion+0x282/0x460 kernel/sched/completion.c:136 __flush_work+0x3d5/0x7f0 kernel/workqueue.c:2928 __cancel_work_timer+0x2f1/0x430 kernel/workqueue.c:3015 cancel_work_sync+0xb/0x10 kernel/workqueue.c:3051 p9_conn_destroy net/9p/trans_fd.c:878 [inline] p9_fd_close+0x267/0x4e0 net/9p/trans_fd.c:913 p9_client_create+0x8f1/0x10f0 net/9p/client.c:1084 v9fs_session_init+0x1ed/0x14c0 fs/9p/v9fs.c:421 v9fs_mount+0x73/0x770 fs/9p/vfs_super.c:135 mount_fs+0x84/0x2a7 fs/super.c:1261 vfs_kern_mount.part.34+0x58/0x3d0 fs/namespace.c:961 vfs_kern_mount fs/namespace.c:951 [inline] do_new_mount fs/namespace.c:2469 [inline] do_mount+0x36e/0x2410 fs/namespace.c:2799 ksys_mount+0xba/0xe0 fs/namespace.c:3015 __do_sys_mount fs/namespace.c:3029 [inline] __se_sys_mount fs/namespace.c:3026 [inline] __x64_sys_mount+0xb9/0x150 fs/namespace.c:3026 do_syscall_64+0xd6/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x458ca9 Code: Bad RIP value. RSP: 002b:00007f50335cbc78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000458ca9 RDX: 0000000020000100 RSI: 00000000200000c0 RDI: 0000000000000000 RBP: 000000000073bf00 R08: 0000000020000140 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f50335cc6d4 R13: 00000000004c4c94 R14: 00000000004d8920 R15: 00000000ffffffff Showing all locks held in the system: 1 lock held by khungtaskd/1038: #0: 000000006757aec6 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4442 2 locks held by kworker/1:3/3220: #0: 00000000322e0981 ((wq_completion)"events"){+.+.}, at: __write_once_size include/linux/compiler.h:220 [inline] #0: 00000000322e0981 ((wq_completion)"events"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: 00000000322e0981 ((wq_completion)"events"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline] #0: 00000000322e0981 ((wq_completion)"events"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:59 [inline] #0: 00000000322e0981 ((wq_completion)"events"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline] #0: 00000000322e0981 ((wq_completion)"events"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: 00000000322e0981 ((wq_completion)"events"){+.+.}, at: process_one_work+0x762/0x1670 kernel/workqueue.c:2126 #1: 000000004bb3ccbd ((work_completion)(&m->rq)){+.+.}, at: process_one_work+0x792/0x1670 kernel/workqueue.c:2130 1 lock held by in:imklog/5711: #0: 0000000035c6bc3a (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1038 Comm: khungtaskd Not tainted 4.19.132-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+0x327/0x3f0 kernel/kthread.c:246 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:415 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 3522 Comm: systemd-journal Not tainted 4.19.132-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:___bpf_prog_run+0x79/0x51b0 kernel/bpf/core.c:1065 Code: 0f b6 04 20 38 d0 7f 08 84 c0 0f 85 c2 35 00 00 0f b6 03 48 8d 3c c5 60 85 ef 86 48 89 c6 48 89 fa 48 c1 ea 03 42 80 3c 22 00 <0f> 85 af 35 00 00 49 8b 04 c6 e9 08 6d 54 05 48 8d 7b 01 48 89 f8 RSP: 0018:ffff888094bbfa08 EFLAGS: 00000246 RAX: 00000000000000a5 RBX: ffffc90001939070 RCX: 1ffff11012977f5c RDX: 1ffffffff0ddf151 RSI: 00000000000000a5 RDI: ffffffff86ef8a88 RBP: ffff888094bbfa70 R08: ffff888094bbffc0 R09: ffff888094bbffd0 R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000 R13: ffffed1012977f5e R14: ffffffff86ef8560 R15: ffff888094bbfae0 FS: 00007fb435a038c0(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fb432dc7000 CR3: 0000000094bd9000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __bpf_prog_run32+0x91/0xd0 kernel/bpf/core.c:1436 seccomp_run_filters+0x113/0x210 kernel/seccomp.c:211 __seccomp_filter+0x9e/0xa60 kernel/seccomp.c:668 __secure_computing+0xc7/0x2e0 kernel/seccomp.c:795 syscall_trace_enter+0x3ce/0x10f0 arch/x86/entry/common.c:121 do_syscall_64+0x38c/0x4e0 arch/x86/entry/common.c:283 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7fb434c9cf17 Code: ff ff ff 48 8b 4d a0 0f b7 51 fe 48 8b 4d a8 66 89 54 08 fe e9 1a ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 b8 27 00 00 00 0f 05 0f 1f 84 00 00 00 00 00 b8 6e 00 00 00 0f 05 c3 0f 1f 84 00 00 RSP: 002b:00007ffcaf5eded8 EFLAGS: 00000206 ORIG_RAX: 0000000000000027 RAX: ffffffffffffffda RBX: 000055f4aa323200 RCX: 00007fb434c9cf17 RDX: 0000000000000000 RSI: ffffffffffffffff RDI: 000055f4aa323200 RBP: 0000000000000dc2 R08: 00007ffcaf5f1000 R09: 000000380a35a3e3 R10: 000d280b9a3fa733 R11: 0000000000000206 R12: ffffffffffffffff R13: 00007ffcaf5edf68 R14: 000055f4a8de3958 R15: 0005aa55028f4e30