syzbot

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ODEBUG: free active (active state 0) object type: work_struct hint: p9_read_work+0x0/0x1060 net/9p/trans_fd.c:208
WARNING: CPU: 1 PID: 8111 at lib/debugobjects.c:329 debug_print_object+0x16a/0x210 lib/debugobjects.c:326
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 8111 Comm: syz-executor368 Not tainted 4.18.0-rc4+ #141
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+0x1c9/0x2b4 lib/dump_stack.c:113
 panic+0x238/0x4e7 kernel/panic.c:184
 __warn.cold.8+0x163/0x1ba kernel/panic.c:536
 report_bug+0x252/0x2d0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992
RIP: 0010:debug_print_object+0x16a/0x210 lib/debugobjects.c:326
Code: 1a 88 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 92 00 00 00 48 8b 14 dd a0 71 1a 88 4c 89 f6 48 c7 c7 40 67 1a 88 e8 c6 94 e6 fd <0f> 0b 83 05 d9 66 3e 06 01 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f 
RSP: 0018:ffff8801a94a72d8 EFLAGS: 00010086
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81631821 RDI: 0000000000000001
RBP: ffff8801a94a7318 R08: ffff8801c3ab81c0 R09: ffffed003b5e3ec2
R10: ffffed003b5e3ec2 R11: ffff8801daf1f617 R12: 0000000000000001
R13: ffffffff88f63820 R14: ffffffff881a6be0 R15: ffffffff814ea9c0
 __debug_check_no_obj_freed lib/debugobjects.c:783 [inline]
 debug_check_no_obj_freed+0x3b2/0x595 lib/debugobjects.c:815
 kfree+0xc7/0x260 mm/slab.c:3812
 p9_fd_close+0x416/0x5b0 net/9p/trans_fd.c:893
 p9_client_create+0xac2/0x16c9 net/9p/client.c:1076
 v9fs_session_init+0x21a/0x1a80 fs/9p/v9fs.c:400
 v9fs_mount+0x7c/0x900 fs/9p/vfs_super.c:135
 mount_fs+0xae/0x328 fs/super.c:1277
 vfs_kern_mount.part.34+0xdc/0x4e0 fs/namespace.c:1037
 vfs_kern_mount fs/namespace.c:1027 [inline]
 do_new_mount fs/namespace.c:2518 [inline]
 do_mount+0x581/0x30e0 fs/namespace.c:2848
 ksys_mount+0x12d/0x140 fs/namespace.c:3064
 __do_sys_mount fs/namespace.c:3078 [inline]
 __se_sys_mount fs/namespace.c:3075 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445d09
Code: e8 ec ba 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 ab 0e fc ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007fce16130da8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00000000006dbc24 RCX: 0000000000445d09
RDX: 00000000200000c0 RSI: 0000000020000040 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000020000100 R09: 0000000000000000
R10: 0000000000200000 R11: 0000000000000202 R12: 00000000006dbc20
R13: 64663d736e617274 R14: 0030656c69662f2e R15: 0000000000000001

======================================================
WARNING: possible circular locking dependency detected
4.18.0-rc4+ #141 Not tainted
------------------------------------------------------
syz-executor368/8111 is trying to acquire lock:
(____ptrval____) ((console_sem).lock){-...}, at: down_trylock+0x13/0x70 kernel/locking/semaphore.c:136

but task is already holding lock:
(____ptrval____) (&obj_hash[i].lock){-.-.}, at: __debug_check_no_obj_freed lib/debugobjects.c:774 [inline]
(____ptrval____) (&obj_hash[i].lock){-.-.}, at: debug_check_no_obj_freed+0x16c/0x595 lib/debugobjects.c:815

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&obj_hash[i].lock){-.-.}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
       __debug_object_init+0x127/0x12e0 lib/debugobjects.c:381
       debug_object_init+0x16/0x20 lib/debugobjects.c:429
       debug_hrtimer_init kernel/time/hrtimer.c:410 [inline]
       debug_init kernel/time/hrtimer.c:458 [inline]
       hrtimer_init+0x97/0x480 kernel/time/hrtimer.c:1308
       init_dl_task_timer+0x1b/0x50 kernel/sched/deadline.c:1056
       __sched_fork+0x2ae/0x590 kernel/sched/core.c:2185
       init_idle+0x75/0x7a0 kernel/sched/core.c:5405
       sched_init+0xbf3/0xd2c kernel/sched/core.c:6103
       start_kernel+0x47d/0x949 init/main.c:602
       x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:452
       x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:433
       secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:242

-> #2 (&rq->lock){-.-.}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
       _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:144
       rq_lock kernel/sched/sched.h:1812 [inline]
       task_fork_fair+0x93/0x680 kernel/sched/fair.c:9952
       sched_fork+0x446/0xb40 kernel/sched/core.c:2381
       copy_process.part.39+0x1c09/0x7220 kernel/fork.c:1773
       copy_process kernel/fork.c:1616 [inline]
       _do_fork+0x291/0x12a0 kernel/fork.c:2099
       kernel_thread+0x34/0x40 kernel/fork.c:2158
       rest_init+0x22/0xe4 init/main.c:408
       start_kernel+0x90e/0x949 init/main.c:738
       x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:452
       x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:433
       secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:242

-> #1 (&p->pi_lock){-.-.}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
       try_to_wake_up+0xd2/0x12b0 kernel/sched/core.c:1985
       wake_up_process+0x10/0x20 kernel/sched/core.c:2148
       __up.isra.1+0x1c0/0x2a0 kernel/locking/semaphore.c:262
       up+0x13c/0x1c0 kernel/locking/semaphore.c:187
       __up_console_sem+0xbe/0x1b0 kernel/printk/printk.c:242
       console_unlock+0x7a2/0x10b0 kernel/printk/printk.c:2411
       vprintk_emit+0x6c6/0xdf0 kernel/printk/printk.c:1907
       vprintk_default+0x28/0x30 kernel/printk/printk.c:1948
       vprintk_func+0x7a/0xe7 kernel/printk/printk_safe.c:382
       printk+0xa7/0xcf kernel/printk/printk.c:1981
       load_umh+0x51/0xbd net/bpfilter/bpfilter_kern.c:98
       do_one_initcall+0x127/0x913 init/main.c:884
       do_initcall_level init/main.c:952 [inline]
       do_initcalls init/main.c:960 [inline]
       do_basic_setup init/main.c:978 [inline]
       kernel_init_freeable+0x49b/0x58e init/main.c:1135
       kernel_init+0x11/0x1b3 init/main.c:1061
       ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

-> #0 ((console_sem).lock){-...}:
       lock_acquire+0x1e4/0x540 kernel/locking/lockdep.c:3924
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
       down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
       __down_trylock_console_sem+0xae/0x200 kernel/printk/printk.c:225
       console_trylock+0x15/0xa0 kernel/printk/printk.c:2230
       console_trylock_spinning kernel/printk/printk.c:1643 [inline]
       vprintk_emit+0x6ad/0xdf0 kernel/printk/printk.c:1906
       vprintk_default+0x28/0x30 kernel/printk/printk.c:1948
       vprintk_func+0x7a/0xe7 kernel/printk/printk_safe.c:382
       printk+0xa7/0xcf kernel/printk/printk.c:1981
       __warn_printk+0x8c/0xe0 kernel/panic.c:590
       debug_print_object+0x16a/0x210 lib/debugobjects.c:326
       __debug_check_no_obj_freed lib/debugobjects.c:783 [inline]
       debug_check_no_obj_freed+0x3b2/0x595 lib/debugobjects.c:815
       kfree+0xc7/0x260 mm/slab.c:3812
       p9_fd_close+0x416/0x5b0 net/9p/trans_fd.c:893
       p9_client_create+0xac2/0x16c9 net/9p/client.c:1076
       v9fs_session_init+0x21a/0x1a80 fs/9p/v9fs.c:400
       v9fs_mount+0x7c/0x900 fs/9p/vfs_super.c:135
       mount_fs+0xae/0x328 fs/super.c:1277
       vfs_kern_mount.part.34+0xdc/0x4e0 fs/namespace.c:1037
       vfs_kern_mount fs/namespace.c:1027 [inline]
       do_new_mount fs/namespace.c:2518 [inline]
       do_mount+0x581/0x30e0 fs/namespace.c:2848
       ksys_mount+0x12d/0x140 fs/namespace.c:3064
       __do_sys_mount fs/namespace.c:3078 [inline]
       __se_sys_mount fs/namespace.c:3075 [inline]
       __x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
       do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
  (console_sem).lock --> &rq->lock --> &obj_hash[i].lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&obj_hash[i].lock);
                               lock(&rq->lock);
                               lock(&obj_hash[i].lock);
  lock((console_sem).lock);

 *** DEADLOCK ***

1 lock held by syz-executor368/8111:
 #0: (____ptrval____) (&obj_hash[i].lock){-.-.}, at: __debug_check_no_obj_freed lib/debugobjects.c:774 [inline]
 #0: (____ptrval____) (&obj_hash[i].lock){-.-.}, at: debug_check_no_obj_freed+0x16c/0x595 lib/debugobjects.c:815

stack backtrace:
CPU: 1 PID: 8111 Comm: syz-executor368 Not tainted 4.18.0-rc4+ #141
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+0x1c9/0x2b4 lib/dump_stack.c:113
 print_circular_bug.isra.36.cold.57+0x1bd/0x27d kernel/locking/lockdep.c:1227
 check_prev_add kernel/locking/lockdep.c:1867 [inline]
 check_prevs_add kernel/locking/lockdep.c:1980 [inline]
 validate_chain kernel/locking/lockdep.c:2421 [inline]
 __lock_acquire+0x3449/0x5020 kernel/locking/lockdep.c:3435
 lock_acquire+0x1e4/0x540 kernel/locking/lockdep.c:3924
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
 down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
 __down_trylock_console_sem+0xae/0x200 kernel/printk/printk.c:225
 console_trylock+0x15/0xa0 kernel/printk/printk.c:2230
 console_trylock_spinning kernel/printk/printk.c:1643 [inline]
 vprintk_emit+0x6ad/0xdf0 kernel/printk/printk.c:1906
 vprintk_default+0x28/0x30 kernel/printk/printk.c:1948
 vprintk_func+0x7a/0xe7 kernel/printk/printk_safe.c:382
 printk+0xa7/0xcf kernel/printk/printk.c:1981
 __warn_printk+0x8c/0xe0 kernel/panic.c:590
 debug_print_object+0x16a/0x210 lib/debugobjects.c:326
 __debug_check_no_obj_freed lib/debugobjects.c:783 [inline]
 debug_check_no_obj_freed+0x3b2/0x595 lib/debugobjects.c:815
 kfree+0xc7/0x260 mm/slab.c:3812
 p9_fd_close+0x416/0x5b0 net/9p/trans_fd.c:893
 p9_client_create+0xac2/0x16c9 net/9p/client.c:1076
 v9fs_session_init+0x21a/0x1a80 fs/9p/v9fs.c:400
 v9fs_mount+0x7c/0x900 fs/9p/vfs_super.c:135
 mount_fs+0xae/0x328 fs/super.c:1277
 vfs_kern_mount.part.34+0xdc/0x4e0 fs/namespace.c:1037
 vfs_kern_mount fs/namespace.c:1027 [inline]
 do_new_mount fs/namespace.c:2518 [inline]
 do_mount+0x581/0x30e0 fs/namespace.c:2848
 ksys_mount+0x12d/0x140 fs/namespace.c:3064
 __do_sys_mount fs/namespace.c:3078 [inline]
 __se_sys_mount fs/namespace.c:3075 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445d09
Code: e8 ec ba 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 ab 0e fc ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007fce16130da8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00000000006dbc24 RCX: 0000000000445d09
RDX: 00000000200000c0 RSI: 0000000020000040 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000020000100 R09: 0000000000000000
R10: 0000000000200000 R11: 0000000000000202 R12: 00000000006dbc20
R13: 64663d736e617274 R14: 0030656c69662f2e R15: 0000000000000001
Shutting down cpus with NMI
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..