bisecting fixing commit since 765675379b6253b6901563e649a2f87d28ada3ff building syzkaller on 143a10e9d6320fa7e38693bd8df375fcf4446ae6 testing commit 765675379b6253b6901563e649a2f87d28ada3ff with gcc (GCC) 8.1.0 kernel signature: 108032e86f074479f1e704541c7307ab02a7d15a5b92dd5a8573fb51e5994d76 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 205a42ce2861f2d0dea8eb5090d05262e1cfa049 testing commit 205a42ce2861f2d0dea8eb5090d05262e1cfa049 with gcc (GCC) 8.1.0 kernel signature: 6e378e74d42c3a83c1e6bf18db1884f8e8b4678af1f61d8a4adfe3f39ef15778 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: crashed: INFO: task hung in d_alloc_parallel run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK revisions tested: 2, total time: 41m47.502189267s (build: 18m42.577694593s, test: 21m52.870349295s) the crash still happens on HEAD commit msg: Linux 4.19.135 crash: INFO: task hung in d_alloc_parallel INFO: task syz-executor.3:15013 blocked for more than 140 seconds. Not tainted 4.19.135-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.3 D28664 15013 6589 0x00000000 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x78c/0x1c10 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 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: 0033:0x45c8a9 Code: Bad RIP value. RSP: 002b:00007fb5e3148c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: 00000000004f6880 RCX: 000000000045c8a9 RDX: 0000000000000049 RSI: 00000000000a8482 RDI: 0000000020000000 RBP: 000000000078c040 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000773 R14: 00000000005251df R15: 00007fb5e31496d4 Showing all locks held in the system: 1 lock held by khungtaskd/1077: #0: 0000000090243b08 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4442 1 lock held by in:imklog/6122: #0: 000000005729f30c (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 1 lock held by syz-executor.0/6581: #0: 00000000a596d1d1 (rcu_preempt_state.exp_mutex){+.+.}, at: exp_funnel_lock kernel/rcu/tree_exp.h:297 [inline] #0: 00000000a596d1d1 (rcu_preempt_state.exp_mutex){+.+.}, at: _synchronize_rcu_expedited+0x3a0/0x8a0 kernel/rcu/tree_exp.h:667 1 lock held by syz-executor.2/6587: #0: 00000000a596d1d1 (rcu_preempt_state.exp_mutex){+.+.}, at: exp_funnel_lock kernel/rcu/tree_exp.h:329 [inline] #0: 00000000a596d1d1 (rcu_preempt_state.exp_mutex){+.+.}, at: _synchronize_rcu_expedited+0x616/0x8a0 kernel/rcu/tree_exp.h:667 2 locks held by syz-executor.3/14981: #0: 00000000095e6e98 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000095e6e98 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000095e6e98 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 00000000f125dbeb (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor.3/15013: #0: 00000000207c8beb (sb_writers#16){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 00000000207c8beb (sb_writers#16){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 00000000095e6e98 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #1: 00000000095e6e98 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #1: 00000000095e6e98 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 1 lock held by syz-executor.4/20286: #0: 00000000317d0285 (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 00000000317d0285 (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 1 lock held by syz-executor.4/20289: #0: 00000000317d0285 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000317d0285 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000317d0285 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 2 locks held by syz-executor.4/20251: #0: 00000000317d0285 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000317d0285 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000317d0285 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 00000000966ce340 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 1 lock held by syz-executor.3/20320: #0: 0000000096ee3034 (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 0000000096ee3034 (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 2 locks held by syz-executor.3/20321: #0: 00000000f1a905e6 (sb_writers#16){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 00000000f1a905e6 (sb_writers#16){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 0000000096ee3034 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #1: 0000000096ee3034 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #1: 0000000096ee3034 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 1 lock held by syz-executor.5/20327: #0: 000000005655842e (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 000000005655842e (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 2 locks held by syz-executor.5/20328: #0: 000000002c753e8c (sb_writers#16){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 000000002c753e8c (sb_writers#16){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 000000005655842e (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #1: 000000005655842e (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #1: 000000005655842e (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 1 lock held by syz-executor.5/20330: #0: 000000005655842e (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 000000005655842e (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 000000005655842e (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 2 locks held by syz-executor.3/20277: #0: 0000000096ee3034 (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 0000000096ee3034 (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 0000000096ee3034 (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 00000000065675e5 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 2 locks held by syz-executor.5/20281: #0: 000000005655842e (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 000000005655842e (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 000000005655842e (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 000000006e05fb90 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 1 lock held by syz-executor.1/20334: #0: 00000000871a70ad (&type->i_mutex_dir_key#8){++++}, at: inode_lock include/linux/fs.h:748 [inline] #0: 00000000871a70ad (&type->i_mutex_dir_key#8){++++}, at: lock_mount+0x82/0x290 fs/namespace.c:2039 2 locks held by syz-executor.1/20335: #0: 000000009f8c73a8 (sb_writers#16){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 000000009f8c73a8 (sb_writers#16){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 00000000871a70ad (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #1: 00000000871a70ad (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #1: 00000000871a70ad (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 2 locks held by syz-executor.1/20302: #0: 00000000871a70ad (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:758 [inline] #0: 00000000871a70ad (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3326 [inline] #0: 00000000871a70ad (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1667/0x3c60 fs/namei.c:3537 #1: 00000000836ed069 (&fi->mutex){+.+.}, at: fuse_lock_inode+0x9a/0xc0 fs/fuse/inode.c:365 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1077 Comm: khungtaskd Not tainted 4.19.135-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: 3695 Comm: systemd-journal Not tainted 4.19.135-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:trace_hardirqs_on+0x36/0x190 kernel/trace/trace_preemptirq.c:31 Code: 53 48 83 ec 08 65 8b 05 b8 4f 9c 7e 85 c0 75 1b 48 8b 5d 08 48 89 df e8 f8 6b e5 ff 48 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d 65 8b 05 b2 c2 9b 7e a9 00 00 10 00 74 11 48 8b 5d 08 65 c7 05 RSP: 0018:ffff8880938aff18 EFLAGS: 00000086 RAX: 0000000000000007 RBX: 0000000000000027 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8880938a4a04 RBP: ffff8880938aff48 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880938aff58 R13: ffffffff885205d8 R14: 0000000000000000 R15: 0000000000000000 FS: 00007f38b28878c0(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000562e7a91cb18 CR3: 00000000938e7000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f38b1b20f17 Code: ff ff ff 48 8b 4d a0 0f b7 51 fe 48 8b 4d a8 66 89 54 08 fe e9 1a ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 b8 27 00 00 00 0f 05 0f 1f 84 00 00 00 00 00 b8 6e 00 00 00 0f 05 c3 0f 1f 84 00 00 RSP: 002b:00007ffd0234ac78 EFLAGS: 00000206 ORIG_RAX: 0000000000000027 RAX: ffffffffffffffda RBX: 0000563893306200 RCX: 00007f38b1b20f17 RDX: 00000000ffffffff RSI: 00007ffd0234ad00 RDI: 0000563893306200 RBP: 0000000000000e6f R08: 00007ffd0235b000 R09: 000000697bf31ead R10: 0011ee5696e49002 R11: 0000000000000206 R12: 00007ffd0234ad00 R13: 00007ffd0234acf8 R14: 0000563893071958 R15: 0005abb1c2759a1d