bisecting fixing commit since 765675379b6253b6901563e649a2f87d28ada3ff building syzkaller on 143a10e9d6320fa7e38693bd8df375fcf4446ae6 testing commit 765675379b6253b6901563e649a2f87d28ada3ff with gcc (GCC) 8.1.0 kernel signature: b076c06d77602b9dc76500b12814e5f6b5eaa57b95683bb5fad89e4bda05d445 run #0: crashed: INFO: task hung in d_alloc_parallel run #1: OK run #2: OK run #3: OK run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK testing current HEAD a39e75458e1ceb7fefaa3a0bd9df21558713cf0d testing commit a39e75458e1ceb7fefaa3a0bd9df21558713cf0d with gcc (GCC) 8.1.0 kernel signature: ba5e272848c6a710c56548cecdf5e8cd5b11d508fa4e7efdbda0aece618a589e run #0: crashed: INFO: task hung in d_alloc_parallel run #1: crashed: INFO: task hung in d_alloc_parallel run #2: OK run #3: OK run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK revisions tested: 2, total time: 37m23.956181071s (build: 17m7.820589985s, test: 19m41.601476094s) the crash still happens on HEAD commit msg: Linux 4.19.130 crash: INFO: task hung in d_alloc_parallel INFO: task syz-executor.4:15099 blocked for more than 140 seconds. Not tainted 4.19.130-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28664 15099 6592 0x00000000 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 d_wait_lookup fs/dcache.c:2428 [inline] d_alloc_parallel+0xdc6/0x1750 fs/dcache.c:2510 lookup_open+0x46e/0x1d30 fs/namei.c:3148 do_last fs/namei.c:3327 [inline] path_openat+0x1683/0x3c60 fs/namei.c:3537 do_filp_open+0x177/0x250 fs/namei.c:3567 do_sys_open+0x1dd/0x350 fs/open.c:1085 __do_sys_open fs/open.c:1103 [inline] __se_sys_open fs/open.c:1098 [inline] __x64_sys_open+0x79/0xb0 fs/open.c:1098 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45c829 Code: Bad RIP value. RSP: 002b:00007fb52cc80c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: 00000000004f6800 RCX: 000000000045c829 RDX: 0000000000000049 RSI: 00000000000a8482 RDI: 0000000020000000 RBP: 000000000078c040 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000773 R14: 000000000052515f R15: 00007fb52cc816d4 Showing all locks held in the system: 1 lock held by khungtaskd/1071: #0: 00000000f1c0fbad (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4442 1 lock held by in:imklog/6025: #0: 00000000a4014907 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 2 locks held by syz-executor.4/15085: #0: 000000003987e3f8 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 000000003987e3f8 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 000000003987e3f8 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 00000000fd16de45 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor.4/15099: #0: 0000000092caf40b (sb_writers#16){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 0000000092caf40b (sb_writers#16){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 000000003987e3f8 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #1: 000000003987e3f8 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #1: 000000003987e3f8 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 1 lock held by syz-executor.1/20838: #0: 00000000b1ce020f (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 00000000b1ce020f (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 2 locks held by syz-executor.1/20839: #0: 00000000d92e4e54 (&rq->lock){-.-.}, at: rq_lock kernel/sched/sched.h:1823 [inline] #0: 00000000d92e4e54 (&rq->lock){-.-.}, at: __schedule+0x1f5/0x1c10 kernel/sched/core.c:3453 #1: 00000000e2694ac5 (&cfs_rq->removed.lock){-.-.}, at: update_cfs_rq_load_avg kernel/sched/fair.c:3490 [inline] #1: 00000000e2694ac5 (&cfs_rq->removed.lock){-.-.}, at: update_load_avg+0xaa8/0x1ac0 kernel/sched/fair.c:3612 1 lock held by syz-executor.0/20845: #0: 000000003fce8132 (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 000000003fce8132 (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 2 locks held by syz-executor.0/20846: #0: 00000000033c3b6c (sb_writers#16){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 00000000033c3b6c (sb_writers#16){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 00000000f1c0fbad (rcu_read_lock){....}, at: trace_sched_stat_runtime include/trace/events/sched.h:428 [inline] #1: 00000000f1c0fbad (rcu_read_lock){....}, at: update_curr+0x2e1/0x890 kernel/sched/fair.c:857 1 lock held by syz-executor.5/20860: #0: 0000000059ba191e (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 0000000059ba191e (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 2 locks held by syz-executor.5/20861: #0: 0000000045793c3d (sb_writers#16){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 0000000045793c3d (sb_writers#16){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 00000000f1c0fbad (rcu_read_lock){....}, at: trace_sched_stat_runtime include/trace/events/sched.h:428 [inline] #1: 00000000f1c0fbad (rcu_read_lock){....}, at: update_curr+0x2e1/0x890 kernel/sched/fair.c:857 1 lock held by syz-executor.4/20875: #0: 00000000d87878eb (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 00000000d87878eb (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 1 lock held by syz-executor.4/20877: #0: 00000000d87878eb (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000d87878eb (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000d87878eb (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 2 locks held by syz-executor.4/20837: #0: 00000000d87878eb (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000d87878eb (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000d87878eb (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 000000001887ead8 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1071 Comm: khungtaskd Not tainted 4.19.130-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 CPU: 0 PID: 3687 Comm: systemd-journal Not tainted 4.19.130-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0033:0x7f16cb21dc2d Code: 0c 00 ba da 00 00 00 e8 21 04 fd ff 90 48 83 ec 08 48 85 ff 74 47 85 f6 78 63 4d 85 c0 74 7e 4c 8b 4f 28 31 c0 4d 85 c9 74 06 <41> 3b 71 08 74 0d 48 83 c4 08 c3 0f 1f 84 00 00 00 00 00 39 57 0c RSP: 002b:00007ffcb5e0c200 EFLAGS: 00000206 RAX: 0000000000000000 RBX: 000000000026f4d0 RCX: 000000000026f4d0 RDX: 0000000000000003 RSI: 0000000000000010 RDI: 00005644844d1140 RBP: 00005644844cd060 R08: 0000000000000065 R09: 00005644844d0dc0 R10: 000556dcfb550062 R11: 0000000000000001 R12: 0000000000000001 R13: 0000000000000003 R14: 0000000000000010 R15: 00005644844d13a0 FS: 00007f16cb5e78c0 GS: 0000000000000000