bisecting fixing commit since c98875d930e915d01e8c40c7d3c16f00b3c8abe1 building syzkaller on b0e8efcb4b0aac61f4647a76bbe54a5d38a370ba testing commit c98875d930e915d01e8c40c7d3c16f00b3c8abe1 with gcc (GCC) 8.1.0 kernel signature: c59efdb3c8056af3be1683b6b71b7f134577bc73df8161b9aa5088eeb0ca553a all runs: crashed: INFO: task hung in p9_fd_close testing current HEAD 258f0cf7ac3b788a14c0d01aab3c4aea02f8c86e testing commit 258f0cf7ac3b788a14c0d01aab3c4aea02f8c86e with gcc (GCC) 8.1.0 kernel signature: 074cf8d27559bf144c19380db73bf3a1f5c5250c1657650759a4995eb4a1e3ad all runs: crashed: INFO: task hung in p9_fd_close revisions tested: 2, total time: 31m17.156233072s (build: 18m10.992855162s, test: 11m48.977406051s) the crash still happens on HEAD commit msg: Linux 4.19.123 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.2:7277 blocked for more than 140 seconds. Not tainted 4.19.123-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D27912 7277 6219 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: 0033:0x458c29 Code: 08 48 c7 44 24 10 04 00 00 00 e8 62 d8 fa ff 48 8b 44 24 18 48 8b 4c 24 30 48 83 c1 08 48 89 0c 24 48 89 44 24 08 48 c7 44 24 <10> 10 00 00 00 e8 3d d8 fa ff 48 8b 44 24 18 48 89 44 24 40 48 8b RSP: 002b:00007fc7e59bec78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000458c29 RDX: 0000000020000100 RSI: 00000000200000c0 RDI: 0000000000000000 RBP: 000000000073bf00 R08: 0000000020000140 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fc7e59bf6d4 R13: 00000000004c4c14 R14: 00000000004d88a0 R15: 00000000ffffffff Showing all locks held in the system: 1 lock held by khungtaskd/1041: #0: 00000000676a8a7e (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4442 2 locks held by kworker/0:3/6409: #0: 00000000ca325b6a ((wq_completion)"events"){+.+.}, at: __write_once_size include/linux/compiler.h:220 [inline] #0: 00000000ca325b6a ((wq_completion)"events"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: 00000000ca325b6a ((wq_completion)"events"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline] #0: 00000000ca325b6a ((wq_completion)"events"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:59 [inline] #0: 00000000ca325b6a ((wq_completion)"events"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline] #0: 00000000ca325b6a ((wq_completion)"events"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: 00000000ca325b6a ((wq_completion)"events"){+.+.}, at: process_one_work+0x762/0x1670 kernel/workqueue.c:2126 #1: 0000000076689c1a ((work_completion)(&m->rq)){+.+.}, at: process_one_work+0x792/0x1670 kernel/workqueue.c:2130 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1041 Comm: khungtaskd Not tainted 4.19.123-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 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 3510 Comm: systemd-journal Not tainted 4.19.123-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0033:0x7ff0118b10e5 Code: b1 00 00 00 4d 85 c9 0f 84 c8 00 00 00 4d 85 c0 0f 84 df 00 00 00 49 8d 2c 08 48 3b 6f 60 48 89 fb 77 42 8d 7e ff 48 8d 43 30 <83> ff 07 bf 00 00 00 00 0f 43 f7 48 83 ec 08 48 8b bb 48 01 00 00 RSP: 002b:00007fffe91cb9a0 EFLAGS: 00000283 RAX: 0000559bb9433ed0 RBX: 0000559bb9433ea0 RCX: 000000000011c2f8 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: 000000000011c349 R08: 0000000000000051 R09: 00007fffe91cb9e0 R10: 00007ff0118ddf1c R11: 000000000052545f R12: 0000000000000001 R13: 00007fffe91cba78 R14: 0000000000000001 R15: 00007fffe91cb9e0 FS: 00007ff011bc28c0 GS: 0000000000000000