bisecting fixing commit since dafd634415a7f9892a6fcc99c540fe567ab42c92 building syzkaller on 8c88c9c1c99c8cd8dabc951164c820b9c9f25114 testing commit dafd634415a7f9892a6fcc99c540fe567ab42c92 with gcc (GCC) 8.1.0 kernel signature: daa4f5b6714bfa32ac5d0a02366114f360d208819e8afbd725dae9a69f8b5824 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: crashed: INFO: task hung in fuse_lookup run #7: OK run #8: OK run #9: OK testing current HEAD b499cf4b3a901e87e1f933df04abf69b54de4457 testing commit b499cf4b3a901e87e1f933df04abf69b54de4457 with gcc (GCC) 8.1.0 kernel signature: b73afa2626aea94b6a5b010c9c7121fcfee5b5b702b4d22a2ad69f1303f91d8a 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 revisions tested: 2, total time: 39m31.285860328s (build: 16m55.573644085s, test: 22m11.598884037s) the crash still happens on HEAD commit msg: Linux 4.19.102 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.3:7529 blocked for more than 140 seconds. Not tainted 4.19.102-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.3 D23832 7529 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:367 __lookup_slow+0x216/0x400 fs/namei.c:1672 lookup_slow+0x51/0x70 fs/namei.c:1689 walk_component+0x694/0x2320 fs/namei.c:1811 link_path_walk.part.40+0x9d7/0x1550 fs/namei.c:2142 link_path_walk fs/namei.c:2073 [inline] path_mountpoint+0xaa/0x1ac0 fs/namei.c:2695 filename_mountpoint.part.58+0x146/0x2f0 fs/namei.c:2718 filename_mountpoint fs/namei.c:2715 [inline] user_path_mountpoint_at+0x35/0x40 fs/namei.c:2748 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: 24 08 48 8d 44 24 68 48 89 44 24 10 e8 42 b9 fa ff eb 0e 48 8d 44 24 68 48 89 04 24 e8 12 bc fa ff 48 8b 44 24 68 48 85 c0 74 <57> 48 8b 4c 24 70 48 8b 09 48 8b 58 08 48 8b 00 48 8b 09 48 85 c9 RSP: 002b:00007ffd434ee7c8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6 RAX: ffffffffffffffda RBX: 000000000003cf8d RCX: 000000000045c487 RDX: 0000000000403550 RSI: 0000000000000002 RDI: 00007ffd434ee870 RBP: 0000000000000002 R08: 0000000000000000 R09: 000000000000000a R10: 0000000000000006 R11: 0000000000000206 R12: 00007ffd434ef900 R13: 0000000001be8940 R14: 0000000000000000 R15: 00007ffd434ef900 Showing all locks held in the system: 1 lock held by khungtaskd/1039: #0: 000000000d8901fd (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4438 1 lock held by rsyslogd/6943: 2 locks held by getty/7067: #0: 00000000f47c65b0 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000a75bf586 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/7068: #0: 000000000fa8dc7b (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 0000000013ce9e4d (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/7069: #0: 00000000acdc3c44 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000006a85e362 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/7070: #0: 00000000ace73688 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 0000000067dd8096 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/7071: #0: 000000008b543be3 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000c09158cb (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/7072: #0: 0000000060852db6 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000148f95f7 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/7073: #0: 000000007eb6f139 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000009bd65687 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by syz-executor.3/7529: #0: 000000007e54852e (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:757 [inline] #0: 000000007e54852e (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x43/0x70 fs/namei.c:1688 #1: 000000008cdbcda8 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor.3/7597: #0: 000000007e54852e (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:757 [inline] #0: 000000007e54852e (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x43/0x70 fs/namei.c:1688 #1: 000000008cdbcda8 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1039 Comm: khungtaskd Not tainted 4.19.102-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 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x12/0x20 arch/x86/include/asm/irqflags.h:60