bisecting fixing commit since dafd634415a7f9892a6fcc99c540fe567ab42c92 building syzkaller on 8c88c9c1c99c8cd8dabc951164c820b9c9f25114 testing commit dafd634415a7f9892a6fcc99c540fe567ab42c92 with gcc (GCC) 8.1.0 kernel signature: d97b49e5f5fa2dcb38b7bf7d6bf9aefff803f92c208be694465433985068d4c5 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 testing current HEAD 5692097116094a4a7045abcc1dbc172dbdc5657e testing commit 5692097116094a4a7045abcc1dbc172dbdc5657e with gcc (GCC) 8.1.0 kernel signature: 9e74620296ed82ab2006579481ae9743dbc781b95a04157401152c4ae1d5c61e 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: OK run #4: OK 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: 40m31.584637487s (build: 17m37.710769784s, test: 22m7.072342501s) the crash still happens on HEAD commit msg: Linux 4.19.109 crash: INFO: task hung in fuse_lookup INFO: task syz-executor.2:7706 blocked for more than 140 seconds. Not tainted 4.19.109-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D24056 7706 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: Bad RIP value. RSP: 002b:00007fff03e3eaa8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a6 RAX: ffffffffffffffda RBX: 000000000005a187 RCX: 000000000045c487 RDX: 0000000000403550 RSI: 0000000000000002 RDI: 00007fff03e3eb50 RBP: 0000000000000002 R08: 0000000000000000 R09: 000000000000000e R10: 000000000000000a R11: 0000000000000202 R12: 00007fff03e3fbe0 R13: 0000000001a63940 R14: 0000000000000000 R15: 00007fff03e3fbe0 Showing all locks held in the system: 2 locks held by init/1: #0: 00000000bb0f9a0f (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:757 [inline] #0: 00000000bb0f9a0f (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x43/0x70 fs/namei.c:1688 #1: 00000000a13be5dc (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 1 lock held by khungtaskd/1019: #0: 00000000c65ec850 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4438 1 lock held by rsyslogd/6949: #0: 000000001f59f52b (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 2 locks held by cron/6999: #0: 00000000bb0f9a0f (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:757 [inline] #0: 00000000bb0f9a0f (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x43/0x70 fs/namei.c:1688 #1: 00000000a13be5dc (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by getty/7071: #0: 000000007a6b7771 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000009024026c (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/7072: #0: 0000000023e3056e (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000f864435a (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/7073: #0: 00000000d4148e95 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000494b9c1f (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/7074: #0: 00000000defe05a9 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 0000000027fb9102 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/7075: #0: 0000000021b220f2 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000005f6fe7cf (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/7076: #0: 00000000b0729825 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000b9bc5122 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/7077: #0: 000000004c132480 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 0000000020019b82 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by syz-executor.2/7706: #0: 0000000088d62c3d (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:757 [inline] #0: 0000000088d62c3d (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x43/0x70 fs/namei.c:1688 #1: 000000003c143d39 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor.2/7764: #0: 0000000088d62c3d (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:757 [inline] #0: 0000000088d62c3d (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x43/0x70 fs/namei.c:1688 #1: 000000003c143d39 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor.5/7783: #0: 0000000050bad8ea (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:757 [inline] #0: 0000000050bad8ea (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x43/0x70 fs/namei.c:1688 #1: 000000007fd355eb (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor186/7824: #0: 00000000bb0f9a0f (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:757 [inline] #0: 00000000bb0f9a0f (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x43/0x70 fs/namei.c:1688 #1: 00000000a13be5dc (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor186/7829: #0: 00000000bb0f9a0f (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:757 [inline] #0: 00000000bb0f9a0f (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x43/0x70 fs/namei.c:1688 #1: 00000000a13be5dc (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1019 Comm: khungtaskd Not tainted 4.19.109-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 CPU: 1 PID: 611 Comm: kworker/u4:4 Not tainted 4.19.109-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_purge_orig RIP: 0010:__lock_acquire+0x1e4/0x4980 kernel/locking/lockdep.c:3290 Code: 0f 85 2a 30 00 00 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 80 3c 02 00 <0f> 85 28 32 00 00 49 81 7d 00 a0 d1 ea 88 0f 84 4a ff ff ff 83 fe RSP: 0018:ffff8880a8d77a10 EFLAGS: 00000046 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 1ffff1100dbfc303 RSI: 0000000000000000 RDI: ffffffff87f20740 RBP: ffff8880a8d77bf8 R08: 0000000000000001 R09: 0000000000000000 R10: ffffed1015d64732 R11: ffff8880aeb23993 R12: 0000000000000000 R13: ffff88806dfe1818 R14: ffff8880a8e583c0 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004ae90f CR3: 0000000098c8a000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: lock_acquire+0x173/0x3d0 kernel/locking/lockdep.c:3903 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168 spin_lock_bh include/linux/spinlock.h:334 [inline] batadv_purge_orig_ref+0x101/0xe80 net/batman-adv/originator.c:1363 batadv_purge_orig+0x14/0x60 net/batman-adv/originator.c:1392 process_one_work+0x830/0x1670 kernel/workqueue.c:2153 worker_thread+0x85/0xb60 kernel/workqueue.c:2296 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415