bisecting fixing commit since dafd634415a7f9892a6fcc99c540fe567ab42c92 building syzkaller on 8c88c9c1c99c8cd8dabc951164c820b9c9f25114 testing commit dafd634415a7f9892a6fcc99c540fe567ab42c92 with gcc (GCC) 8.1.0 kernel signature: 2088bdfff2420d327ed88958722a4a0c51b0af3a 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 fb683b5e3f53a73e761952735736180939a313df testing commit fb683b5e3f53a73e761952735736180939a313df with gcc (GCC) 8.1.0 kernel signature: 8157632d6926b95afaba1a5c15fc1971e55c1800 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: 39m20.69118722s (build: 16m51.498277545s, test: 22m1.648717755s) the crash still happens on HEAD commit msg: Linux 4.19.88 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.5:7239 blocked for more than 140 seconds. Not tainted 4.19.88-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D23832 7239 1 0x00000004 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 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3617 __mutex_lock_common kernel/locking/mutex.c:1002 [inline] __mutex_lock+0x806/0x1210 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 fuse_lookup+0x89/0x3b0 fs/fuse/dir.c:360 __lookup_slow+0x216/0x400 fs/namei.c:1671 lookup_slow+0x51/0x70 fs/namei.c:1688 walk_component+0x694/0x2320 fs/namei.c:1810 link_path_walk.part.41+0x9d7/0x1550 fs/namei.c:2141 link_path_walk fs/namei.c:2072 [inline] path_mountpoint+0xaa/0x1ac0 fs/namei.c:2694 filename_mountpoint.part.59+0x146/0x2f0 fs/namei.c:2717 filename_mountpoint fs/namei.c:2714 [inline] user_path_mountpoint_at+0x35/0x40 fs/namei.c:2747 ksys_umount+0x12e/0xcc0 fs/namespace.c:1645 __do_sys_umount fs/namespace.c:1671 [inline] __se_sys_umount fs/namespace.c:1669 [inline] __x64_sys_umount+0x4f/0x70 fs/namespace.c:1669 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45c487 Code: Bad RIP value. RSP: 002b:00007fffa5424398 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6 RAX: ffffffffffffffda RBX: 000000000001e3be RCX: 000000000045c487 RDX: 0000000000403550 RSI: 0000000000000002 RDI: 00007fffa5424440 RBP: 0000000000000002 R08: 0000000000000000 R09: 000000000000000a R10: 0000000000000006 R11: 0000000000000206 R12: 00007fffa54254d0 R13: 000000000166b940 R14: 0000000000000000 R15: 00007fffa54254d0 Showing all locks held in the system: 1 lock held by khungtaskd/1039: #0: 00000000563dfe3a (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4438 3 locks held by kworker/u4:5/2762: #0: 000000009fc38446 (&rq->lock){-.-.}, at: rq_lock kernel/sched/sched.h:1817 [inline] #0: 000000009fc38446 (&rq->lock){-.-.}, at: __schedule+0x1f5/0x1c10 kernel/sched/core.c:3453 #1: 00000000563dfe3a (rcu_read_lock){....}, at: __update_idle_core+0x45/0x3f0 kernel/sched/fair.c:5989 #2: 0000000090dc3545 (&base->lock){-.-.}, at: lock_timer_base+0xc8/0x160 kernel/time/timer.c:938 1 lock held by rsyslogd/6869: 2 locks held by getty/6991: #0: 00000000f9b02b6b (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000efd9b511 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by getty/6992: #0: 00000000d5bc3ebd (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000be944e62 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by getty/6993: #0: 00000000a29ef59b (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000000daaf2d7 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by getty/6994: #0: 0000000010f48bf6 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000f889fffa (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by getty/6995: #0: 00000000dd9c3439 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000abadc282 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by getty/6996: #0: 000000007f7110e9 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 0000000065abf807 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by getty/6997: #0: 00000000d78c6565 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000001b28ca90 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x18d0 drivers/tty/n_tty.c:2154 2 locks held by syz-executor.5/7239: #0: 0000000033dd664c (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:757 [inline] #0: 0000000033dd664c (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x43/0x70 fs/namei.c:1687 #1: 00000000d65fa1e8 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor.5/7321: #0: 0000000033dd664c (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:757 [inline] #0: 0000000033dd664c (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x43/0x70 fs/namei.c:1687 #1: 00000000d65fa1e8 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor.1/7349: #0: 0000000099627da7 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:757 [inline] #0: 0000000099627da7 (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x43/0x70 fs/namei.c:1687 #1: 00000000d4f86906 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1039 Comm: khungtaskd Not tainted 4.19.88-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 skipped: idling at native_safe_halt+0x12/0x20 arch/x86/include/asm/irqflags.h:60