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SubjectRe: unregister_netdevice: waiting for DEV to become free (2)
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Date
Hello people involved in commit a3e23f719f5c4a38 ("net-sysfs: call dev_hold if kobject_init_and_add success")
and commit b8eb718348b8fb30 ("net-sysfs: Fix reference count leak in rx|netdev_queue_add_kobject").

syzbot is reporting that unregister_netdevice() hangs due to underflowing
device refcount when kobject_init_and_add() failed due to -ENOMEM.

----------
11:25:02 executing program 3 (fault-call:5 fault-nth:2):
r0 = openat$tun(0xffffffffffffff9c, &(0x7f0000000100)='/dev/net/tun\x00', 0x0, 0x0)
ioctl$TUNSETIFF(r0, 0x400454ca, &(0x7f0000000000)={'vet\x00\x00\x00\x00\x00\x00\x00\x00\x00\xbdh\x00', 0x43732e5398416f1a})
ioctl$TUNSETQUEUE(r0, 0x400454d9, &(0x7f00000000c0)={'\x00', 0x400})
r1 = openat$tun(0xffffffffffffff9c, &(0x7f0000000080)='/dev/net/tun\x00', 0x0, 0x0)
ioctl$TUNSETIFF(r1, 0x400454ca, &(0x7f0000000000)={'vet\x00\x00\x00\x00\x00\x00\x00\x00\x00\xbdh\x00', 0x43732e5398416f1a})
ioctl$TUNSETQUEUE(r0, 0x400454d9, &(0x7f0000000040)={'lo\x00', 0x200})
----------

----------
[ 60.043899] IPVS: ftp: loaded support on port[0] = 21
[ 60.275782] chnl_net:caif_netlink_parms(): no params data found
[ 60.305039] bridge0: port 1(bridge_slave_0) entered blocking state
[ 60.305551] bridge0: port 1(bridge_slave_0) entered disabled state
[ 60.306366] device bridge_slave_0 entered promiscuous mode
[ 60.311776] bridge0: port 2(bridge_slave_1) entered blocking state
[ 60.312032] bridge0: port 2(bridge_slave_1) entered disabled state
[ 60.312858] device bridge_slave_1 entered promiscuous mode
[ 60.336705] bond0: (slave bond_slave_0): Enslaving as an active interface with an up link
[ 60.338321] bond0: (slave bond_slave_1): Enslaving as an active interface with an up link
[ 60.357851] team0: Port device team_slave_0 added
[ 60.359250] team0: Port device team_slave_1 added
[ 60.522829] device hsr_slave_0 entered promiscuous mode
[ 60.651798] device hsr_slave_1 entered promiscuous mode
[ 60.790287] netdevsim netdevsim0 netdevsim0: renamed from eth0
[ 60.854953] netdevsim netdevsim0 netdevsim1: renamed from eth1
[ 60.911733] netdevsim netdevsim0 netdevsim2: renamed from eth2
[ 60.974063] netdevsim netdevsim0 netdevsim3: renamed from eth3
[ 61.109590] bridge0: port 2(bridge_slave_1) entered blocking state
[ 61.109922] bridge0: port 2(bridge_slave_1) entered forwarding state
[ 61.110384] bridge0: port 1(bridge_slave_0) entered blocking state
[ 61.110556] bridge0: port 1(bridge_slave_0) entered forwarding state
[ 61.151643] 8021q: adding VLAN 0 to HW filter on device bond0
[ 61.156692] IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
[ 61.164101] bridge0: port 1(bridge_slave_0) entered disabled state
[ 61.190521] bridge0: port 2(bridge_slave_1) entered disabled state
[ 61.230466] IPv6: ADDRCONF(NETDEV_CHANGE): bond0: link becomes ready
[ 61.283759] 8021q: adding VLAN 0 to HW filter on device team0
[ 61.364323] IPv6: ADDRCONF(NETDEV_CHANGE): bridge_slave_0: link becomes ready
[ 61.366383] bridge0: port 1(bridge_slave_0) entered blocking state
[ 61.366568] bridge0: port 1(bridge_slave_0) entered forwarding state
[ 61.367033] IPv6: ADDRCONF(NETDEV_CHANGE): bridge_slave_1: link becomes ready
[ 61.367556] bridge0: port 2(bridge_slave_1) entered blocking state
[ 61.367727] bridge0: port 2(bridge_slave_1) entered forwarding state
[ 61.372342] IPv6: ADDRCONF(NETDEV_CHANGE): team_slave_0: link becomes ready
[ 61.377760] IPv6: ADDRCONF(NETDEV_CHANGE): team_slave_1: link becomes ready
[ 61.381755] IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_0: link becomes ready
[ 61.383474] IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_1: link becomes ready
[ 61.386511] IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes ready
[ 61.405483] 8021q: adding VLAN 0 to HW filter on device batadv0
[ 61.408968] IPv6: ADDRCONF(NETDEV_CHANGE): team0: link becomes ready
[ 61.412478] IPv6: ADDRCONF(NETDEV_CHANGE): vxcan1: link becomes ready
[ 61.414712] IPv6: ADDRCONF(NETDEV_CHANGE): vxcan0: link becomes ready
[ 61.466051] FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 1
[ 61.468544] CPU: 6 PID: 6365 Comm: syz-executor Not tainted 5.4.0+ #223
[ 61.469778] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/29/2019
[ 61.473052] Call Trace:
[ 61.475277] dump_stack+0x163/0x1d5
[ 61.476597] should_fail+0x655/0x740
[ 61.477847] ? fault_create_debugfs_attr+0x170/0x170
[ 61.479192] ? ___might_sleep+0x1de/0x500
[ 61.480520] __should_failslab+0xde/0x130
[ 61.481834] should_failslab+0x9/0x14
[ 61.483145] kmem_cache_alloc+0x28e/0x770
[ 61.484448] ? memcpy+0x45/0x50
[ 61.486397] ? kstrdup+0x59/0x70
[ 61.488702] __kernfs_new_node+0xde/0x6f0
[ 61.490999] ? kernfs_dop_revalidate+0x380/0x380
[ 61.493038] ? __put_user_ns+0x60/0x60
[ 61.495621] ? mark_lock+0x11f/0xc60
[ 61.497768] ? put_dec+0xc0/0xc0
[ 61.499926] kernfs_new_node+0x97/0x110
[ 61.501971] kernfs_create_dir_ns+0x4d/0x150
[ 61.504019] sysfs_create_dir_ns+0x13b/0x2a0
[ 61.505973] ? sysfs_create_mount_point+0xb0/0xb0
[ 61.507978] ? rwlock_bug.part.2+0x90/0x90
[ 61.509917] ? lock_acquire+0x19f/0x3f0
[ 61.511893] ? __kasan_check_read+0x11/0x20
[ 61.513887] ? do_raw_spin_unlock+0x54/0x260
[ 61.515829] kobject_add_internal+0x223/0x9a0
[ 61.517825] kobject_init_and_add+0xff/0x170
[ 61.519811] ? kset_create_and_add+0x180/0x180
[ 61.521849] ? lock_acquire+0x19f/0x3f0
[ 61.523865] ? rtnl_lock+0x17/0x20
[ 61.525787] netdev_queue_update_kobjects+0xeb/0x370
[ 61.527816] netif_set_real_num_tx_queues+0x188/0x740
[ 61.530219] ? mutex_lock_io_nested+0x14b0/0x14b0
[ 61.532255] tun_attach+0x4bd/0x1250
[ 61.534231] ? lock_acquire+0x19f/0x3f0
[ 61.536130] __tun_chr_ioctl+0x6fd/0x3b50
[ 61.537960] ? tun_flow_update+0xba0/0xba0
[ 61.539709] ? __kasan_check_read+0x11/0x20
[ 61.541376] ? mark_lock+0x11f/0xc60
[ 61.543057] ? _kstrtoull+0x11c/0x1c0
[ 61.544725] ? __kasan_check_read+0x11/0x20
[ 61.546556] ? __lock_acquire+0xc5c/0x3b30
[ 61.548282] ? __kasan_check_read+0x11/0x20
[ 61.550033] ? mark_lock+0x11f/0xc60
[ 61.551749] ? __kasan_check_read+0x11/0x20
[ 61.553502] ? __lock_acquire+0xc5c/0x3b30
[ 61.555247] ? __fget+0x31c/0x4d0
[ 61.556976] ? tun_chr_compat_ioctl+0x50/0x50
[ 61.558743] tun_chr_ioctl+0x2a/0x40
[ 61.560255] ? tun_chr_ioctl+0x2a/0x40
[ 61.562490] do_vfs_ioctl+0x1a2/0x1150
[ 61.564138] ? rcu_read_lock_held+0x9c/0xb0
[ 61.565830] ? ioctl_preallocate+0x1e0/0x1e0
[ 61.567495] ? __fget+0x33e/0x4d0
[ 61.569168] ? do_dup2+0x4d0/0x4d0
[ 61.570928] ? fput_many+0xe6/0x150
[ 61.572618] ? fput+0x1a/0x20
[ 61.574382] ? security_file_ioctl+0x81/0xb0
[ 61.576049] ksys_ioctl+0x94/0xb0
[ 61.577783] __x64_sys_ioctl+0x73/0xb0
[ 61.579526] do_syscall_64+0xde/0x6c0
[ 61.581302] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 61.583010] RIP: 0033:0x45a729
[ 61.584734] Code: bd b1 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 8b b1 fb ff c3 66 2e 0f 1f 84 00 00 00 00
[ 61.590407] RSP: 002b:00007f25d540ec88 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[ 61.592488] RAX: ffffffffffffffda RBX: 000000000071bf00 RCX: 000000000045a729
[ 61.594552] RDX: 0000000020000040 RSI: 00000000400454d9 RDI: 0000000000000003
[ 61.596829] RBP: 00007f25d540eca0 R08: 0000000000000000 R09: 0000000000000000
[ 61.598540] R10: 0000000000000000 R11: 0000000000000246 R12: 00007f25d540f6d4
[ 61.600278] R13: 00000000004ac5a5 R14: 00000000006ee8a0 R15: 0000000000000005
[ 61.655323] kobject_add_internal failed for tx-1 (error: -12 parent: queues)
[ 71.760970] unregister_netdevice: waiting for vet to become free. Usage count = -1
[ 82.028434] unregister_netdevice: waiting for vet to become free. Usage count = -1
[ 92.140031] unregister_netdevice: waiting for vet to become free. Usage count = -1
----------

Worrisome part is that tun_attach() calls tun_set_real_num_queues() at the end of tun_attach()
but tun_set_real_num_queues() is not handling netif_set_real_num_tx_queues() failure.
That is, tun_attach() is returning success even if netdev_queue_update_kobjects() from
netif_set_real_num_tx_queues() failed.

static void tun_set_real_num_queues(struct tun_struct *tun)
{
netif_set_real_num_tx_queues(tun->dev, tun->numqueues);
netif_set_real_num_rx_queues(tun->dev, tun->numqueues);
}

And I guess that ignoring that failure causes clean-up function to drop a refcount
which was not held by initialization function. Applying below diff seems to avoid
this problem. Please check.

----------
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index ae3bcb1540ec..562d06c274aa 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1459,14 +1459,14 @@ static int netdev_queue_add_kobject(struct net_device *dev, int index)
struct kobject *kobj = &queue->kobj;
int error = 0;

+ dev_hold(queue->dev);
+
kobj->kset = dev->queues_kset;
error = kobject_init_and_add(kobj, &netdev_queue_ktype, NULL,
"tx-%u", index);
if (error)
goto err;

- dev_hold(queue->dev);
-
#ifdef CONFIG_BQL
error = sysfs_create_group(kobj, &dql_group);
if (error)
----------
----------
[ 64.482925] IPVS: ftp: loaded support on port[0] = 21
[ 64.684701] chnl_net:caif_netlink_parms(): no params data found
[ 64.757440] bridge0: port 1(bridge_slave_0) entered blocking state
[ 64.757596] bridge0: port 1(bridge_slave_0) entered disabled state
[ 64.760043] device bridge_slave_0 entered promiscuous mode
[ 64.761799] bridge0: port 2(bridge_slave_1) entered blocking state
[ 64.762025] bridge0: port 2(bridge_slave_1) entered disabled state
[ 64.793334] device bridge_slave_1 entered promiscuous mode
[ 64.818373] bond0: (slave bond_slave_0): Enslaving as an active interface with an up link
[ 64.822950] bond0: (slave bond_slave_1): Enslaving as an active interface with an up link
[ 64.843403] team0: Port device team_slave_0 added
[ 64.844859] team0: Port device team_slave_1 added
[ 64.933830] device hsr_slave_0 entered promiscuous mode
[ 64.972990] device hsr_slave_1 entered promiscuous mode
[ 65.048057] netdevsim netdevsim0 netdevsim0: renamed from eth0
[ 65.113612] netdevsim netdevsim0 netdevsim1: renamed from eth1
[ 65.191758] netdevsim netdevsim0 netdevsim2: renamed from eth2
[ 65.262611] netdevsim netdevsim0 netdevsim3: renamed from eth3
[ 65.339507] bridge0: port 2(bridge_slave_1) entered blocking state
[ 65.339821] bridge0: port 2(bridge_slave_1) entered forwarding state
[ 65.340340] bridge0: port 1(bridge_slave_0) entered blocking state
[ 65.340514] bridge0: port 1(bridge_slave_0) entered forwarding state
[ 65.486729] 8021q: adding VLAN 0 to HW filter on device bond0
[ 65.545043] IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
[ 65.567266] bridge0: port 1(bridge_slave_0) entered disabled state
[ 65.592695] bridge0: port 2(bridge_slave_1) entered disabled state
[ 65.631471] IPv6: ADDRCONF(NETDEV_CHANGE): bond0: link becomes ready
[ 65.656557] 8021q: adding VLAN 0 to HW filter on device team0
[ 65.660768] IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_bridge: link becomes ready
[ 65.661411] IPv6: ADDRCONF(NETDEV_CHANGE): bridge_slave_0: link becomes ready
[ 65.661949] bridge0: port 1(bridge_slave_0) entered blocking state
[ 65.662127] bridge0: port 1(bridge_slave_0) entered forwarding state
[ 65.693984] IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bridge: link becomes ready
[ 65.697297] IPv6: ADDRCONF(NETDEV_CHANGE): bridge_slave_1: link becomes ready
[ 65.701488] bridge0: port 2(bridge_slave_1) entered blocking state
[ 65.703895] bridge0: port 2(bridge_slave_1) entered forwarding state
[ 65.706370] IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_bond: link becomes ready
[ 65.724296] hsr0: Slave A (hsr_slave_0) is not up; please bring it up to get a fully working HSR network
[ 65.728690] hsr0: Slave B (hsr_slave_1) is not up; please bring it up to get a fully working HSR network
[ 65.777203] IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bond: link becomes ready
[ 65.782476] IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_team: link becomes ready
[ 65.785989] IPv6: ADDRCONF(NETDEV_CHANGE): team_slave_0: link becomes ready
[ 65.789006] IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_team: link becomes ready
[ 65.796973] IPv6: ADDRCONF(NETDEV_CHANGE): team_slave_1: link becomes ready
[ 65.801313] IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_hsr: link becomes ready
[ 65.804748] IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_0: link becomes ready
[ 65.807939] IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_hsr: link becomes ready
[ 65.811874] IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_1: link becomes ready
[ 65.814814] IPv6: ADDRCONF(NETDEV_CHANGE): team0: link becomes ready
[ 65.824311] IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes ready
[ 65.835888] 8021q: adding VLAN 0 to HW filter on device batadv0
[ 65.840711] IPv6: ADDRCONF(NETDEV_CHANGE): vxcan1: link becomes ready
[ 65.843289] IPv6: ADDRCONF(NETDEV_CHANGE): vxcan0: link becomes ready
[ 66.055083] FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 1
[ 66.058933] CPU: 1 PID: 6375 Comm: syz-executor Not tainted 5.4.0+ #224
[ 66.060904] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/29/2019
[ 66.065868] Call Trace:
[ 66.068993] dump_stack+0x163/0x1d5
[ 66.071611] should_fail+0x655/0x740
[ 66.074082] ? fault_create_debugfs_attr+0x170/0x170
[ 66.076772] ? ___might_sleep+0x1de/0x500
[ 66.079324] __should_failslab+0xde/0x130
[ 66.082540] should_failslab+0x9/0x14
[ 66.084806] kmem_cache_alloc+0x28e/0x770
[ 66.087262] ? memcpy+0x45/0x50
[ 66.089712] ? kstrdup+0x59/0x70
[ 66.092133] __kernfs_new_node+0xde/0x6f0
[ 66.094512] ? kernfs_dop_revalidate+0x380/0x380
[ 66.096934] ? __put_user_ns+0x60/0x60
[ 66.099303] ? mark_lock+0x11f/0xc60
[ 66.101585] ? put_dec+0xc0/0xc0
[ 66.104388] kernfs_new_node+0x97/0x110
[ 66.106537] kernfs_create_dir_ns+0x4d/0x150
[ 66.108622] sysfs_create_dir_ns+0x13b/0x2a0
[ 66.110584] ? sysfs_create_mount_point+0xb0/0xb0
[ 66.112769] ? rwlock_bug.part.2+0x90/0x90
[ 66.114866] ? lock_acquire+0x19f/0x3f0
[ 66.116925] ? __kasan_check_read+0x11/0x20
[ 66.118888] ? do_raw_spin_unlock+0x54/0x260
[ 66.120909] kobject_add_internal+0x223/0x9a0
[ 66.122835] kobject_init_and_add+0xff/0x170
[ 66.124860] ? kset_create_and_add+0x180/0x180
[ 66.126944] ? lock_acquire+0x19f/0x3f0
[ 66.129143] ? rtnl_lock+0x17/0x20
[ 66.131087] netdev_queue_update_kobjects+0x118/0x390
[ 66.133028] ? __kasan_check_read+0x11/0x20
[ 66.134944] netif_set_real_num_tx_queues+0x188/0x740
[ 66.137012] ? mutex_lock_io_nested+0x14b0/0x14b0
[ 66.139043] tun_attach+0x4bd/0x1250
[ 66.140950] ? lock_acquire+0x19f/0x3f0
[ 66.142870] __tun_chr_ioctl+0x6fd/0x3b50
[ 66.144724] ? tun_flow_update+0xba0/0xba0
[ 66.146532] ? __kasan_check_read+0x11/0x20
[ 66.148821] ? mark_lock+0x11f/0xc60
[ 66.150635] ? _kstrtoull+0x11c/0x1c0
[ 66.152399] ? __kasan_check_read+0x11/0x20
[ 66.154056] ? __lock_acquire+0xc5c/0x3b30
[ 66.155701] ? __kasan_check_read+0x11/0x20
[ 66.157438] ? mark_lock+0x11f/0xc60
[ 66.159265] ? __kasan_check_read+0x11/0x20
[ 66.161032] ? __lock_acquire+0xc5c/0x3b30
[ 66.162885] ? __fget+0x31c/0x4d0
[ 66.164619] ? tun_chr_compat_ioctl+0x50/0x50
[ 66.166104] tun_chr_ioctl+0x2a/0x40
[ 66.167538] ? tun_chr_ioctl+0x2a/0x40
[ 66.169199] do_vfs_ioctl+0x1a2/0x1150
[ 66.170969] ? rcu_read_lock_held+0x9c/0xb0
[ 66.172735] ? ioctl_preallocate+0x1e0/0x1e0
[ 66.174487] ? __fget+0x33e/0x4d0
[ 66.176170] ? do_dup2+0x4d0/0x4d0
[ 66.177866] ? fput_many+0xe6/0x150
[ 66.179520] ? fput+0x1a/0x20
[ 66.181176] ? security_file_ioctl+0x81/0xb0
[ 66.182909] ksys_ioctl+0x94/0xb0
[ 66.184452] __x64_sys_ioctl+0x73/0xb0
[ 66.186169] do_syscall_64+0xde/0x6c0
[ 66.187908] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 66.189678] RIP: 0033:0x45a729
[ 66.191328] Code: bd b1 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 8b b1 fb ff c3 66 2e 0f 1f 84 00 00 00 00
[ 66.196839] RSP: 002b:00007f08f9987c88 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[ 66.198849] RAX: ffffffffffffffda RBX: 000000000071bf00 RCX: 000000000045a729
[ 66.200876] RDX: 0000000020000040 RSI: 00000000400454d9 RDI: 0000000000000003
[ 66.202947] RBP: 00007f08f9987ca0 R08: 0000000000000000 R09: 0000000000000000
[ 66.204491] R10: 0000000000000000 R11: 0000000000000246 R12: 00007f08f99886d4
[ 66.205688] R13: 00000000004ac5a5 R14: 00000000006ee8a0 R15: 0000000000000005
[ 66.277453] kobject_add_internal failed for tx-1 (error: -12 parent: queues)
[ 67.499501] syz-executor (6368) used greatest stack depth: 23704 bytes left
[ 70.237146] tipc: TX() has been purged, node left!
[ 75.794671] device bridge_slave_1 left promiscuous mode
[ 75.797354] bridge0: port 2(bridge_slave_1) entered disabled state
[ 75.861863] device bridge_slave_0 left promiscuous mode
[ 75.864646] bridge0: port 1(bridge_slave_0) entered disabled state
[ 79.752910] device hsr_slave_0 left promiscuous mode
[ 79.841067] device hsr_slave_1 left promiscuous mode
[ 79.939879] team0 (unregistering): Port device team_slave_1 removed
[ 79.963767] team0 (unregistering): Port device team_slave_0 removed
[ 79.985156] bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
[ 80.090348] bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
[ 80.352617] bond0 (unregistering): Released all slaves
----------
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