bisecting fixing commit since b98aebd298246df37b472c52a2ee1023256d02e3 building syzkaller on b24d2b8a213c09b511478e7eab5fa343e4a198de testing commit b98aebd298246df37b472c52a2ee1023256d02e3 with gcc (GCC) 8.1.0 kernel signature: eb5268ebaa279d48a241b6983d353d534b42c89cf539923e48f63b8ea070f80e run #0: crashed: INFO: task hung in fuse_lookup run #1: crashed: INFO: task hung in fuse_lookup run #2: crashed: INFO: task hung in fuse_lookup run #3: crashed: INFO: task hung in fuse_lookup run #4: crashed: INFO: task hung in fuse_lookup run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK testing current HEAD 12cd844a39ed16aa183a820a54fe6f9a0bb4cd14 testing commit 12cd844a39ed16aa183a820a54fe6f9a0bb4cd14 with gcc (GCC) 8.1.0 kernel signature: a3ee5d5348979d3fb878a8b7bdfdb1dad2108e3af8fe7b4b80377956a4434dd0 run #0: crashed: INFO: task hung in fuse_lookup run #1: crashed: INFO: task hung in fuse_lookup run #2: crashed: INFO: task hung in fuse_lookup run #3: crashed: INFO: task hung in fuse_lookup run #4: crashed: INFO: task hung in fuse_lookup run #5: crashed: INFO: task hung in fuse_lookup run #6: OK run #7: OK run #8: OK run #9: OK revisions tested: 2, total time: 40m21.782327002s (build: 17m27.893798768s, test: 22m7.045244955s) the crash still happens on HEAD commit msg: Linux 4.14.173 crash: INFO: task hung in fuse_lookup team0 (unregistering): Port device team_slave_0 removed bond0 (unregistering): Releasing backup interface bond_slave_1 bond0 (unregistering): Releasing backup interface bond_slave_0 bond0 (unregistering): Released all slaves INFO: task syz-executor.3:7329 blocked for more than 140 seconds. Not tainted 4.14.173-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.3 D24504 7329 1 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 fuse_lock_inode+0x9f/0xd0 fs/fuse/inode.c:365 fuse_lookup+0x7a/0x380 fs/fuse/dir.c:367 lookup_slow+0x20f/0x3f0 fs/namei.c:1696 walk_component+0x680/0x21a0 fs/namei.c:1825 link_path_walk+0x9be/0x1540 fs/namei.c:2154 path_mountpoint+0xa3/0x1a40 fs/namei.c:2718 filename_mountpoint.part.54+0x141/0x2d0 fs/namei.c:2745 filename_mountpoint fs/namei.c:2742 [inline] user_path_mountpoint_at+0x35/0x40 fs/namei.c:2775 SYSC_umount fs/namespace.c:1730 [inline] SyS_umount+0x109/0x3a0 fs/namespace.c:1714 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45c487 RSP: 002b:00007fff3e4c3438 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6 RAX: ffffffffffffffda RBX: 000000000003deea RCX: 000000000045c487 RDX: 0000000000403550 RSI: 0000000000000002 RDI: 00007fff3e4c34e0 RBP: 0000000000000002 R08: 0000000000000000 R09: 000000000000000e R10: 000000000000000a R11: 0000000000000206 R12: 00007fff3e4c4570 R13: 00000000027c9940 R14: 0000000000000000 R15: 00007fff3e4c4570 INFO: task syz-executor.1:7370 blocked for more than 140 seconds. Not tainted 4.14.173-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D24872 7370 1 0x00000004 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 fuse_lock_inode+0x9f/0xd0 fs/fuse/inode.c:365 fuse_lookup+0x7a/0x380 fs/fuse/dir.c:367 lookup_slow+0x20f/0x3f0 fs/namei.c:1696 walk_component+0x680/0x21a0 fs/namei.c:1825 link_path_walk+0x9be/0x1540 fs/namei.c:2154 path_mountpoint+0xa3/0x1a40 fs/namei.c:2718 filename_mountpoint.part.54+0x141/0x2d0 fs/namei.c:2745 filename_mountpoint fs/namei.c:2742 [inline] user_path_mountpoint_at+0x35/0x40 fs/namei.c:2775 SYSC_umount fs/namespace.c:1730 [inline] SyS_umount+0x109/0x3a0 fs/namespace.c:1714 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45c487 RSP: 002b:00007ffdec543728 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6 RAX: ffffffffffffffda RBX: 000000000003f352 RCX: 000000000045c487 RDX: 0000000000403550 RSI: 0000000000000002 RDI: 00007ffdec5437d0 RBP: 0000000000000002 R08: 0000000000000000 R09: 000000000000000e R10: 000000000000000a R11: 0000000000000206 R12: 00007ffdec544860 R13: 0000000000ac7940 R14: 0000000000000000 R15: 00007ffdec544860 Showing all locks held in the system: 1 lock held by khungtaskd/1017: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4544 2 locks held by getty/6850: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6851: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6852: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6853: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6854: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6855: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6856: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.3/7329: #0: (&type->i_mutex_dir_key#7){++++}, at: [] inode_lock_shared include/linux/fs.h:728 [inline] #0: (&type->i_mutex_dir_key#7){++++}, at: [] lookup_slow+0x123/0x3f0 fs/namei.c:1674 #1: (&fi->mutex){+.+.}, at: [] fuse_lock_inode+0x9f/0xd0 fs/fuse/inode.c:365 2 locks held by syz-executor.3/7365: #0: (&type->i_mutex_dir_key#7){++++}, at: [] inode_lock_shared include/linux/fs.h:728 [inline] #0: (&type->i_mutex_dir_key#7){++++}, at: [] lookup_slow+0x123/0x3f0 fs/namei.c:1674 #1: (&fi->mutex){+.+.}, at: [] fuse_lock_inode+0x9f/0xd0 fs/fuse/inode.c:365 2 locks held by syz-executor.1/7370: #0: (&type->i_mutex_dir_key#7){++++}, at: [] inode_lock_shared include/linux/fs.h:728 [inline] #0: (&type->i_mutex_dir_key#7){++++}, at: [] lookup_slow+0x123/0x3f0 fs/namei.c:1674 #1: (&fi->mutex){+.+.}, at: [] fuse_lock_inode+0x9f/0xd0 fs/fuse/inode.c:365 2 locks held by syz-executor.1/7406: #0: (&type->i_mutex_dir_key#7){++++}, at: [] inode_lock_shared include/linux/fs.h:728 [inline] #0: (&type->i_mutex_dir_key#7){++++}, at: [] lookup_slow+0x123/0x3f0 fs/namei.c:1674 #1: (&fi->mutex){+.+.}, at: [] fuse_lock_inode+0x9f/0xd0 fs/fuse/inode.c:365 2 locks held by syz-executor.4/7413: #0: (&type->i_mutex_dir_key#7){++++}, at: [] inode_lock_shared include/linux/fs.h:728 [inline] #0: (&type->i_mutex_dir_key#7){++++}, at: [] lookup_slow+0x123/0x3f0 fs/namei.c:1674 #1: (&fi->mutex){+.+.}, at: [] fuse_lock_inode+0x9f/0xd0 fs/fuse/inode.c:365 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1017 Comm: khungtaskd Not tainted 4.14.173-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xf7/0x13b lib/dump_stack.c:58 nmi_cpu_backtrace.cold.4+0x3e/0x76 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xe5/0x119 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:140 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline] watchdog+0x522/0xb40 kernel/hung_task.c:274 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff86221842