======================================================
WARNING: possible circular locking dependency detected
kobject: 'kvm' (00000000a3800bbf): kobject_uevent_env
4.20.0-rc6-next-20181217+ #172 Not tainted
------------------------------------------------------
syz-executor3/8239 is trying to acquire lock:
000000002547212a (&tbl->lock){+.-.}, at: neigh_change_state+0x1dc/0x7a0 net/core/neighbour.c:141
kobject: 'kvm' (00000000a3800bbf): fill_kobj_path: path = '/devices/virtual/misc/kvm'

but task is already holding lock:
00000000de1512fb (&n->lock){++--}, at: __neigh_update+0xe6/0x1eb0 net/core/neighbour.c:1203

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&n->lock){++--}:
       __raw_write_lock include/linux/rwlock_api_smp.h:210 [inline]
       _raw_write_lock+0x2d/0x40 kernel/locking/spinlock.c:288
       neigh_periodic_work+0x3c0/0xc30 net/core/neighbour.c:894
       process_one_work+0xc90/0x1c40 kernel/workqueue.c:2153
       worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
       kthread+0x35a/0x440 kernel/kthread.c:246
       ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

-> #0 (&tbl->lock){+.-.}:
       lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3841
       __raw_write_lock_bh include/linux/rwlock_api_smp.h:203 [inline]
       _raw_write_lock_bh+0x31/0x40 kernel/locking/spinlock.c:312
       neigh_change_state+0x1dc/0x7a0 net/core/neighbour.c:141
       __neigh_update+0x478/0x1eb0 net/core/neighbour.c:1302
       neigh_add+0x613/0xd90 net/core/neighbour.c:1899
       rtnetlink_rcv_msg+0x46a/0xc20 net/core/rtnetlink.c:4971
       netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2477
       rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4989
       netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
       netlink_unicast+0x5a5/0x760 net/netlink/af_netlink.c:1336
       netlink_sendmsg+0xa18/0xfc0 net/netlink/af_netlink.c:1917
kobject: 'loop1' (00000000cc0be2c0): kobject_uevent_env
       sock_sendmsg_nosec net/socket.c:622 [inline]
       sock_sendmsg+0xd5/0x120 net/socket.c:632
       ___sys_sendmsg+0x7fd/0x930 net/socket.c:2117
       __sys_sendmsg+0x11d/0x280 net/socket.c:2155
       __do_sys_sendmsg net/socket.c:2164 [inline]
       __se_sys_sendmsg net/socket.c:2162 [inline]
       __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
       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:

kobject: 'loop1' (00000000cc0be2c0): fill_kobj_path: path = '/devices/virtual/block/loop1'
 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&n->lock);
                               lock(&tbl->lock);
                               lock(&n->lock);
  lock(&tbl->lock);

 *** DEADLOCK ***

2 locks held by syz-executor3/8239:
 #0: 000000001b7ee1aa (rtnl_mutex){+.+.}, at: rtnl_lock net/core/rtnetlink.c:77 [inline]
 #0: 000000001b7ee1aa (rtnl_mutex){+.+.}, at: rtnetlink_rcv_msg+0x40e/0xc20 net/core/rtnetlink.c:4968
 #1: 00000000de1512fb (&n->lock){++--}, at: __neigh_update+0xe6/0x1eb0 net/core/neighbour.c:1203
kobject: 'loop2' (00000000983ef0b3): kobject_uevent_env

stack backtrace:
CPU: 1 PID: 8239 Comm: syz-executor3 Not tainted 4.20.0-rc6-next-20181217+ #172
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+0x244/0x39d lib/dump_stack.c:113
kobject: 'loop2' (00000000983ef0b3): fill_kobj_path: path = '/devices/virtual/block/loop2'
 print_circular_bug.isra.36.cold.58+0x1bd/0x27d kernel/locking/lockdep.c:1224
 check_prev_add kernel/locking/lockdep.c:1866 [inline]
 check_prevs_add kernel/locking/lockdep.c:1979 [inline]
 validate_chain kernel/locking/lockdep.c:2350 [inline]
 __lock_acquire+0x3399/0x4c20 kernel/locking/lockdep.c:3338
 lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3841
 __raw_write_lock_bh include/linux/rwlock_api_smp.h:203 [inline]
 _raw_write_lock_bh+0x31/0x40 kernel/locking/spinlock.c:312
 neigh_change_state+0x1dc/0x7a0 net/core/neighbour.c:141
kobject: 'kvm' (00000000a3800bbf): kobject_uevent_env
kobject: 'kvm' (00000000a3800bbf): fill_kobj_path: path = '/devices/virtual/misc/kvm'
 __neigh_update+0x478/0x1eb0 net/core/neighbour.c:1302
 neigh_add+0x613/0xd90 net/core/neighbour.c:1899
 rtnetlink_rcv_msg+0x46a/0xc20 net/core/rtnetlink.c:4971
 netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2477
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4989
 netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
 netlink_unicast+0x5a5/0x760 net/netlink/af_netlink.c:1336
 netlink_sendmsg+0xa18/0xfc0 net/netlink/af_netlink.c:1917
kobject: 'loop1' (00000000cc0be2c0): kobject_uevent_env
kobject: 'loop1' (00000000cc0be2c0): fill_kobj_path: path = '/devices/virtual/block/loop1'
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:632
 ___sys_sendmsg+0x7fd/0x930 net/socket.c:2117
kobject: 'kvm' (00000000a3800bbf): kobject_uevent_env
kobject: 'kvm' (00000000a3800bbf): fill_kobj_path: path = '/devices/virtual/misc/kvm'
 __sys_sendmsg+0x11d/0x280 net/socket.c:2155
kobject: 'kvm' (00000000a3800bbf): kobject_uevent_env
 __do_sys_sendmsg net/socket.c:2164 [inline]
 __se_sys_sendmsg net/socket.c:2162 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
kobject: 'kvm' (00000000a3800bbf): fill_kobj_path: path = '/devices/virtual/misc/kvm'
kobject: 'kvm' (00000000a3800bbf): kobject_uevent_env
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457669
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
kobject: 'kvm' (00000000a3800bbf): fill_kobj_path: path = '/devices/virtual/misc/kvm'
RSP: 002b:00007f58e9727c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457669
RDX: 0000000000000000 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f58e97286d4
R13: 00000000004c3e94 R14: 00000000004d6d20 R15: 00000000ffffffff
kobject: 'loop0' (00000000bdf78471): kobject_uevent_env
kobject: 'kvm' (00000000a3800bbf): kobject_uevent_env
kobject: 'kvm' (00000000a3800bbf): fill_kobj_path: path = '/devices/virtual/misc/kvm'
kobject: 'loop0' (00000000bdf78471): fill_kobj_path: path = '/devices/virtual/block/loop0'
kobject: 'loop3' (00000000e3cb11a9): kobject_uevent_env
kobject: 'loop3' (00000000e3cb11a9): fill_kobj_path: path = '/devices/virtual/block/loop3'
kobject: 'kvm' (00000000a3800bbf): kobject_uevent_env
kobject: 'loop1' (00000000cc0be2c0): kobject_uevent_env
kobject: 'loop1' (00000000cc0be2c0): fill_kobj_path: path = '/devices/virtual/block/loop1'
kobject: 'kvm' (00000000a3800bbf): fill_kobj_path: path = '/devices/virtual/misc/kvm'
kobject: 'loop5' (00000000f4178d66): kobject_uevent_env
kobject: 'loop5' (00000000f4178d66): fill_kobj_path: path = '/devices/virtual/block/loop5'
kobject: 'loop3' (00000000e3cb11a9): kobject_uevent_env
==================================================================
BUG: KASAN: slab-out-of-bounds in memset include/linux/string.h:337 [inline]
BUG: KASAN: slab-out-of-bounds in fpstate_init+0x50/0x160 arch/x86/kernel/fpu/core.c:178
Write of size 832 at addr ffff8881b12a2bc0 by task syz-executor0/8273

CPU: 0 PID: 8273 Comm: syz-executor0 Not tainted 4.20.0-rc6-next-20181217+ #172
kobject: 'kvm' (00000000a3800bbf): kobject_uevent_env
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+0x244/0x39d lib/dump_stack.c:113
kobject: 'kvm' (00000000a3800bbf): fill_kobj_path: path = '/devices/virtual/misc/kvm'
 print_address_description.cold.4+0x9/0x1ff mm/kasan/report.c:187
 kasan_report.cold.5+0x1b/0x39 mm/kasan/report.c:317
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x13e/0x1b0 mm/kasan/generic.c:191
 memset+0x23/0x40 mm/kasan/common.c:113
 memset include/linux/string.h:337 [inline]
 fpstate_init+0x50/0x160 arch/x86/kernel/fpu/core.c:178
 fx_init arch/x86/kvm/x86.c:8646 [inline]
 kvm_arch_vcpu_init+0x3e9/0x870 arch/x86/kvm/x86.c:9006
 kvm_vcpu_init+0x2fa/0x420 arch/x86/kvm/../../../virt/kvm/kvm_main.c:315
 vmx_create_vcpu+0x1b7/0x2695 arch/x86/kvm/vmx/vmx.c:6375
 kvm_arch_vcpu_create+0xe5/0x220 arch/x86/kvm/x86.c:8679
 kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:2555 [inline]
 kvm_vm_ioctl+0x526/0x2030 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3084
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x1de/0x1790 fs/ioctl.c:696
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457669
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f177b43ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457669
RDX: 0000000000000000 RSI: 000000000000ae41 RDI: 0000000000000004
RBP: 000000000072c040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f177b43b6d4
R13: 00000000004c00ff R14: 00000000004d1170 R15: 00000000ffffffff

Allocated by task 8273:
 save_stack+0x43/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 kasan_kmalloc+0xcb/0xd0 mm/kasan/common.c:482
 kasan_slab_alloc+0x12/0x20 mm/kasan/common.c:397
 kmem_cache_alloc+0x130/0x730 mm/slab.c:3541
 kmem_cache_zalloc include/linux/slab.h:730 [inline]
 vmx_create_vcpu+0x110/0x2695 arch/x86/kvm/vmx/vmx.c:6366
 kvm_arch_vcpu_create+0xe5/0x220 arch/x86/kvm/x86.c:8679
 kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:2555 [inline]
 kvm_vm_ioctl+0x526/0x2030 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3084
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x1de/0x1790 fs/ioctl.c:696
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8881b12a2b80
 which belongs to the cache x86_fpu of size 832
The buggy address is located 64 bytes inside of
 832-byte region [ffff8881b12a2b80, ffff8881b12a2ec0)
The buggy address belongs to the page:
page:ffffea0006c4a880 count:1 mapcount:0 mapping:ffff8881d7930680 index:0x0
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 ffff8881d71b3248 ffff8881d71b3248 ffff8881d7930680
raw: 0000000000000000 ffff8881b12a2040 0000000100000004 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881b12a2d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881b12a2e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8881b12a2e80: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
                                           ^
 ffff8881b12a2f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881b12a2f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
kobject: 'loop3' (00000000e3cb11a9): fill_kobj_path: path = '/devices/virtual/block/loop3'