bisecting fixing commit since c98875d930e915d01e8c40c7d3c16f00b3c8abe1 building syzkaller on b0e8efcb4b0aac61f4647a76bbe54a5d38a370ba testing commit c98875d930e915d01e8c40c7d3c16f00b3c8abe1 with gcc (GCC) 8.1.0 kernel signature: 97bb2342cf80690f7cb3ec6547fbc8d4ec635688f41f9724456ad61d955717c3 all runs: crashed: INFO: task hung in p9_fd_close testing current HEAD 3fc898571b974f9a05e4e5c1fe17b18548207091 testing commit 3fc898571b974f9a05e4e5c1fe17b18548207091 with gcc (GCC) 8.1.0 kernel signature: bf5b98f9fa38f680039432670eae70b72cbe2140cfb60788ae048230cce2fedb all runs: crashed: INFO: task hung in p9_fd_close revisions tested: 2, total time: 28m13.757390964s (build: 16m23.186373129s, test: 11m21.076008179s) the crash still happens on HEAD commit msg: Linux 4.19.128 crash: INFO: task hung in p9_fd_close 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 8021q: adding VLAN 0 to HW filter on device batadv0 INFO: task syz-executor.0:7247 blocked for more than 140 seconds. Not tainted 4.19.128-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D27912 7247 6253 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: Bad RIP value. RSP: 002b:00007fdde218ac78 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: 00007fdde218b6d4 R13: 00000000004c4c14 R14: 00000000004d88a0 R15: 00000000ffffffff Showing all locks held in the system: 1 lock held by khungtaskd/1037: #0: 0000000049ab9188 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4442 2 locks held by kworker/0:2/3516: #0: 0000000063b560b3 ((wq_completion)"events"){+.+.}, at: __write_once_size include/linux/compiler.h:220 [inline] #0: 0000000063b560b3 ((wq_completion)"events"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: 0000000063b560b3 ((wq_completion)"events"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline] #0: 0000000063b560b3 ((wq_completion)"events"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:59 [inline] #0: 0000000063b560b3 ((wq_completion)"events"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline] #0: 0000000063b560b3 ((wq_completion)"events"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: 0000000063b560b3 ((wq_completion)"events"){+.+.}, at: process_one_work+0x762/0x1670 kernel/workqueue.c:2126 #1: 00000000a58079fa ((work_completion)(&m->rq)){+.+.}, at: process_one_work+0x792/0x1670 kernel/workqueue.c:2130 1 lock held by in:imklog/5729: #0: 00000000d77076d2 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1037 Comm: khungtaskd Not tainted 4.19.128-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: 137 Comm: kworker/u4:2 Not tainted 4.19.128-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_nc_worker RIP: 0010:lock_release+0x3f4/0x850 kernel/locking/lockdep.c:3928 Code: 77 01 00 00 65 4c 8b 24 25 40 ee 01 00 49 8d bc 24 84 08 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 14 02 <48> 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 32 03 00 00 48 RSP: 0018:ffff8880a9487c58 EFLAGS: 00000807 RAX: dffffc0000000000 RBX: 1ffff11015290f8f RCX: 1ffff1101528b99f RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffff8880a945cd04 RBP: ffff8880a9487d00 R08: 0000000000000000 R09: ffffed1015d64732 R10: ffffed1015d64732 R11: ffff8880aeb23993 R12: ffff8880a945c480 R13: 0000000000000002 R14: 764cce0ee22c2ac3 R15: ffff8880a945c480 FS: 0000000000000000(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f3553f26000 CR3: 0000000095571000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: rcu_lock_release include/linux/rcupdate.h:247 [inline] rcu_read_unlock include/linux/rcupdate.h:681 [inline] batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:423 [inline] batadv_nc_worker+0x191/0x630 net/batman-adv/network-coding.c:730 process_one_work+0x835/0x1670 kernel/workqueue.c:2155 worker_thread+0x85/0xb60 kernel/workqueue.c:2298 kthread+0x327/0x3f0 kernel/kthread.c:246 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:415