bisecting fixing commit since 765675379b6253b6901563e649a2f87d28ada3ff building syzkaller on 143a10e9d6320fa7e38693bd8df375fcf4446ae6 testing commit 765675379b6253b6901563e649a2f87d28ada3ff with gcc (GCC) 8.1.0 kernel signature: 2a4470ba7479751e34b543ebd44368d21a05610c42b15911be9950d65ce439ba 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 2d16cf4817bc6944a2adb5bf4db607c8258e87da testing commit 2d16cf4817bc6944a2adb5bf4db607c8258e87da with gcc (GCC) 8.1.0 kernel signature: 6869b95cbd253dc9fe508e4593bbdb68cf048d51a8cd9f9aa8d4516425132b32 run #0: crashed: INFO: task hung in d_alloc_parallel run #1: crashed: INFO: task hung in d_alloc_parallel run #2: crashed: INFO: task hung in d_alloc_parallel run #3: crashed: INFO: task hung in d_alloc_parallel run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK revisions tested: 2, total time: 37m50.801240839s (build: 17m40.174727807s, test: 19m27.730085282s) the crash still happens on HEAD commit msg: Linux 4.19.125 crash: INFO: task hung in d_alloc_parallel INFO: task syz-executor.4:13866 blocked for more than 140 seconds. Not tainted 4.19.125-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28664 13866 6575 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: 0d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f69fd66cc78 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: 00007f69fd66d6d4 Showing all locks held in the system: 1 lock held by khungtaskd/1083: #0: 00000000babc857e (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4442 2 locks held by in:imklog/6026: #0: 00000000167e810a (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 #1: 00000000fb5cf27c (&rq->lock){-.-.}, at: rq_lock kernel/sched/sched.h:1823 [inline] #1: 00000000fb5cf27c (&rq->lock){-.-.}, at: __schedule+0x1f5/0x1c10 kernel/sched/core.c:3453 2 locks held by syz-executor.4/13830: #0: 00000000a8a68233 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000a8a68233 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000a8a68233 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 000000005e75f3f8 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor.4/13866: #0: 000000007d984c34 (sb_writers#15){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 000000007d984c34 (sb_writers#15){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 00000000a8a68233 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #1: 00000000a8a68233 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #1: 00000000a8a68233 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 1 lock held by syz-executor.5/19453: #0: 000000004c81acb3 (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 000000004c81acb3 (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 2 locks held by syz-executor.5/19454: #0: 00000000337c2241 (sb_writers#15){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 00000000337c2241 (sb_writers#15){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 000000004c81acb3 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #1: 000000004c81acb3 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #1: 000000004c81acb3 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 1 lock held by syz-executor.5/19459: #0: 000000004c81acb3 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 000000004c81acb3 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 000000004c81acb3 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 2 locks held by syz-executor.5/19410: #0: 000000004c81acb3 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 000000004c81acb3 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 000000004c81acb3 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 00000000cc06370d (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 1 lock held by syz-executor.0/19460: #0: 00000000cfff868b (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 00000000cfff868b (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 2 locks held by syz-executor.0/19461: #0: 00000000a8cc9769 (sb_writers#15){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 00000000a8cc9769 (sb_writers#15){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 00000000cfff868b (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #1: 00000000cfff868b (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #1: 00000000cfff868b (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 1 lock held by syz-executor.0/19462: #0: 00000000cfff868b (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000cfff868b (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000cfff868b (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 2 locks held by syz-executor.0/19426: #0: 00000000cfff868b (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000cfff868b (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000cfff868b (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 000000006b5e8636 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 1 lock held by syz-executor.3/19467: #0: 00000000e9a9f237 (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 00000000e9a9f237 (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 2 locks held by syz-executor.3/19468: #0: 000000006fa9a2e2 (sb_writers#15){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 000000006fa9a2e2 (sb_writers#15){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 00000000e9a9f237 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #1: 00000000e9a9f237 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #1: 00000000e9a9f237 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 1 lock held by syz-executor.3/19476: #0: 00000000e9a9f237 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000e9a9f237 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000e9a9f237 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 1 lock held by syz-executor.1/19470: #0: 000000004832b225 (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 000000004832b225 (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 2 locks held by syz-executor.1/19471: #0: 0000000055151a56 (sb_writers#15){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 0000000055151a56 (sb_writers#15){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 000000004832b225 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #1: 000000004832b225 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #1: 000000004832b225 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 1 lock held by syz-executor.1/19480: #0: 000000004832b225 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 000000004832b225 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 000000004832b225 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 1 lock held by syz-executor.4/19474: #0: 00000000aeefc14b (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 00000000aeefc14b (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 2 locks held by syz-executor.4/19481: #0: 0000000042d5523a (sb_writers#15){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 0000000042d5523a (sb_writers#15){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 00000000aeefc14b (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #1: 00000000aeefc14b (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #1: 00000000aeefc14b (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 1 lock held by syz-executor.4/19486: #0: 00000000aeefc14b (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000aeefc14b (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000aeefc14b (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 2 locks held by syz-executor.3/19440: #0: 00000000e9a9f237 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000e9a9f237 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000e9a9f237 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 0000000099f971fd (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor.1/19443: #0: 000000004832b225 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 000000004832b225 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 000000004832b225 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 00000000e7625912 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor.4/19446: #0: 00000000aeefc14b (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000aeefc14b (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000aeefc14b (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 00000000ed9d0166 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1083 Comm: khungtaskd Not tainted 4.19.125-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: 6572 Comm: syz-executor.2 Not tainted 4.19.125-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:util_est_dequeue kernel/sched/fair.c:3760 [inline] RIP: 0010:dequeue_task_fair+0x24e/0x6e0 kernel/sched/fair.c:5282 Code: 03 42 0f b6 14 38 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 e3 03 00 00 41 8b 96 c0 01 00 00 85 d2 0f 84 62 ff ff ff <48> 8b 45 c8 4c 8d b0 78 01 00 00 48 b8 00 00 00 00 00 fc ff df 4c RSP: 0018:ffff88809b42f810 EFLAGS: 00000006 RAX: ffff8880aea2c280 RBX: 0000000000000000 RCX: 1ffff11010c308ba RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8880aea2c2b8 RBP: ffff88809b42f858 R08: 0000000000000000 R09: 00000000000002d5 R10: 00000052801bd473 R11: ffff8880aea23993 R12: 0000000000000009 R13: dffffc0000000000 R14: 0000000000000158 R15: ffff8880aea2c340 FS: 0000000002c8f940(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f9416506018 CR3: 000000009ee4d000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: dequeue_task kernel/sched/core.c:739 [inline] deactivate_task+0xee/0x340 kernel/sched/core.c:755 __schedule+0x8e6/0x1c10 kernel/sched/core.c:3465 schedule+0x7f/0x1b0 kernel/sched/core.c:3559 schedule_timeout+0x6d5/0xda0 kernel/time/timer.c:1782 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common kernel/sched/completion.c:115 [inline] wait_for_completion+0x282/0x460 kernel/sched/completion.c:136 __wait_rcu_gp+0x260/0x350 kernel/rcu/update.c:368 synchronize_rcu.part.63+0xe0/0xf0 kernel/rcu/tree_plugin.h:820 synchronize_rcu+0x27/0xa0 kernel/rcu/tree_plugin.h:821 namespace_unlock+0xd7/0xf0 fs/namespace.c:1363 do_umount fs/namespace.c:1565 [inline] ksys_umount+0x5e1/0xcc0 fs/namespace.c:1660 __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: 0033:0x45f257 Code: 64 89 04 25 d0 02 00 00 58 5f ff d0 48 89 c7 e8 8f be ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 ad 8c fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fff2a4caad8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6 RAX: ffffffffffffffda RBX: 000000000005a9ce RCX: 000000000045f257 RDX: 0000000000402ff8 RSI: 0000000000000002 RDI: 00007fff2a4cab80 RBP: 00000000000003f0 R08: 0000000000000000 R09: 000000000000000b R10: 0000000000000005 R11: 0000000000000206 R12: 00007fff2a4cbc10 R13: 0000000002c90940 R14: 0000000000000000 R15: 00007fff2a4cbc10