net: deadlock between ip_expire/sch_direct_xmit

[Dmitry Vyukov]

Hello,

I've got the following deadlock report while running syzkaller fuzzer
on net-next/92cd12c5ed432c5eebd2462d666772a8d8442c3b:


[ INFO: possible circular locking dependency detected ]
4.10.0+ #29 Not tainted
-------------------------------------------------------
modprobe/12392 is trying to acquire lock:
(_xmit_ETHER#2){+.-...}, at: [<ffffffff837a8182>] spin_lock
include/linux/spinlock.h:299 [inline]
(_xmit_ETHER#2){+.-...}, at: [<ffffffff837a8182>] __netif_tx_lock
include/linux/netdevice.h:3486 [inline]
(_xmit_ETHER#2){+.-...}, at: [<ffffffff837a8182>]
sch_direct_xmit+0x282/0x6d0 net/sched/sch_generic.c:180

but task is already holding lock:
(&(&q->lock)->rlock){+.-...}, at: [<ffffffff8389a4d1>] spin_lock
include/linux/spinlock.h:299 [inline]
(&(&q->lock)->rlock){+.-...}, at: [<ffffffff8389a4d1>]
ip_expire+0x51/0x6c0 net/ipv4/ip_fragment.c:201

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&(&q->lock)->rlock){+.-...}:
validate_chain kernel/locking/lockdep.c:2267 [inline]
__lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x33/0x50 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:299 [inline]
ip_defrag+0x3a2/0x4130 net/ipv4/ip_fragment.c:669
ip_check_defrag+0x4e3/0x8b0 net/ipv4/ip_fragment.c:713
packet_rcv_fanout+0x282/0x800 net/packet/af_packet.c:1459
deliver_skb net/core/dev.c:1834 [inline]
dev_queue_xmit_nit+0x294/0xa90 net/core/dev.c:1890
xmit_one net/core/dev.c:2903 [inline]
dev_hard_start_xmit+0x16b/0xab0 net/core/dev.c:2923
sch_direct_xmit+0x31f/0x6d0 net/sched/sch_generic.c:182
__dev_xmit_skb net/core/dev.c:3092 [inline]
__dev_queue_xmit+0x13e5/0x1e60 net/core/dev.c:3358
dev_queue_xmit+0x17/0x20 net/core/dev.c:3423
neigh_resolve_output+0x6b9/0xb10 net/core/neighbour.c:1308
neigh_output include/net/neighbour.h:478 [inline]
ip_finish_output2+0x8b8/0x15a0 net/ipv4/ip_output.c:228
ip_do_fragment+0x1d93/0x2720 net/ipv4/ip_output.c:672
ip_fragment.constprop.54+0x145/0x200 net/ipv4/ip_output.c:545
ip_finish_output+0x82d/0xe10 net/ipv4/ip_output.c:314
NF_HOOK_COND include/linux/netfilter.h:246 [inline]
ip_output+0x1f0/0x7a0 net/ipv4/ip_output.c:404
dst_output include/net/dst.h:486 [inline]
ip_local_out+0x95/0x170 net/ipv4/ip_output.c:124
ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1492
ip_push_pending_frames+0x64/0x80 net/ipv4/ip_output.c:1512
raw_sendmsg+0x26de/0x3a00 net/ipv4/raw.c:655
inet_sendmsg+0x164/0x5b0 net/ipv4/af_inet.c:761
sock_sendmsg_nosec net/socket.c:633 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:643
___sys_sendmsg+0x4a3/0x9f0 net/socket.c:1985
__sys_sendmmsg+0x25c/0x750 net/socket.c:2075
SYSC_sendmmsg net/socket.c:2106 [inline]
SyS_sendmmsg+0x35/0x60 net/socket.c:2101
do_syscall_64+0x2e8/0x930 arch/x86/entry/common.c:281
return_from_SYSCALL_64+0x0/0x7a

-> #0 (_xmit_ETHER#2){+.-...}:
check_prev_add kernel/locking/lockdep.c:1830 [inline]
check_prevs_add+0xa8f/0x19f0 kernel/locking/lockdep.c:1940
validate_chain kernel/locking/lockdep.c:2267 [inline]
__lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x33/0x50 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:299 [inline]
__netif_tx_lock include/linux/netdevice.h:3486 [inline]
sch_direct_xmit+0x282/0x6d0 net/sched/sch_generic.c:180
__dev_xmit_skb net/core/dev.c:3092 [inline]
__dev_queue_xmit+0x13e5/0x1e60 net/core/dev.c:3358
dev_queue_xmit+0x17/0x20 net/core/dev.c:3423
neigh_hh_output include/net/neighbour.h:468 [inline]
neigh_output include/net/neighbour.h:476 [inline]
ip_finish_output2+0xf6c/0x15a0 net/ipv4/ip_output.c:228
ip_finish_output+0xa29/0xe10 net/ipv4/ip_output.c:316
NF_HOOK_COND include/linux/netfilter.h:246 [inline]
ip_output+0x1f0/0x7a0 net/ipv4/ip_output.c:404
dst_output include/net/dst.h:486 [inline]
ip_local_out+0x95/0x170 net/ipv4/ip_output.c:124
ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1492
ip_push_pending_frames+0x64/0x80 net/ipv4/ip_output.c:1512
icmp_push_reply+0x372/0x4d0 net/ipv4/icmp.c:394
icmp_send+0x156c/0x1c80 net/ipv4/icmp.c:754
ip_expire+0x40e/0x6c0 net/ipv4/ip_fragment.c:239
call_timer_fn+0x241/0x820 kernel/time/timer.c:1268
expire_timers kernel/time/timer.c:1307 [inline]
__run_timers+0x960/0xcf0 kernel/time/timer.c:1601
run_timer_softirq+0x21/0x80 kernel/time/timer.c:1614
__do_softirq+0x31f/0xbe7 kernel/softirq.c:284
invoke_softirq kernel/softirq.c:364 [inline]
irq_exit+0x1cc/0x200 kernel/softirq.c:405
exiting_irq arch/x86/include/asm/apic.h:657 [inline]
smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:962
apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:707
__read_once_size include/linux/compiler.h:254 [inline]
atomic_read arch/x86/include/asm/atomic.h:26 [inline]
rcu_dynticks_curr_cpu_in_eqs kernel/rcu/tree.c:350 [inline]
__rcu_is_watching kernel/rcu/tree.c:1133 [inline]
rcu_is_watching+0x83/0x110 kernel/rcu/tree.c:1147
rcu_read_lock_held+0x87/0xc0 kernel/rcu/update.c:293
radix_tree_deref_slot include/linux/radix-tree.h:238 [inline]
filemap_map_pages+0x6d4/0x1570 mm/filemap.c:2335
do_fault_around mm/memory.c:3231 [inline]
do_read_fault mm/memory.c:3265 [inline]
do_fault+0xbd5/0x2080 mm/memory.c:3370
handle_pte_fault mm/memory.c:3600 [inline]
__handle_mm_fault+0x1062/0x2cb0 mm/memory.c:3714
handle_mm_fault+0x1e2/0x480 mm/memory.c:3751
__do_page_fault+0x4f6/0xb60 arch/x86/mm/fault.c:1397
do_page_fault+0x54/0x70 arch/x86/mm/fault.c:1460
page_fault+0x28/0x30 arch/x86/entry/entry_64.S:1011

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&(&q->lock)->rlock);
lock(_xmit_ETHER#2);
lock(&(&q->lock)->rlock);
lock(_xmit_ETHER#2);

*** DEADLOCK ***

10 locks held by modprobe/12392:
#0: (&mm->mmap_sem){++++++}, at: [<ffffffff81329758>]
__do_page_fault+0x2b8/0xb60 arch/x86/mm/fault.c:1336
#1: (rcu_read_lock){......}, at: [<ffffffff8188cab6>]
filemap_map_pages+0x1e6/0x1570 mm/filemap.c:2324
#2: (&(ptlock_ptr(page))->rlock#2){+.+...}, at: [<ffffffff81984a78>]
spin_lock include/linux/spinlock.h:299 [inline]
#2: (&(ptlock_ptr(page))->rlock#2){+.+...}, at: [<ffffffff81984a78>]
pte_alloc_one_map mm/memory.c:2944 [inline]
#2: (&(ptlock_ptr(page))->rlock#2){+.+...}, at: [<ffffffff81984a78>]
alloc_set_pte+0x13b8/0x1b90 mm/memory.c:3072
#3: (((&q->timer))){+.-...}, at: [<ffffffff81627e72>]
lockdep_copy_map include/linux/lockdep.h:175 [inline]
#3: (((&q->timer))){+.-...}, at: [<ffffffff81627e72>]
call_timer_fn+0x1c2/0x820 kernel/time/timer.c:1258
#4: (&(&q->lock)->rlock){+.-...}, at: [<ffffffff8389a4d1>] spin_lock
include/linux/spinlock.h:299 [inline]
#4: (&(&q->lock)->rlock){+.-...}, at: [<ffffffff8389a4d1>]
ip_expire+0x51/0x6c0 net/ipv4/ip_fragment.c:201
#5: (rcu_read_lock){......}, at: [<ffffffff8389a633>]
ip_expire+0x1b3/0x6c0 net/ipv4/ip_fragment.c:216
#6: (slock-AF_INET){+.-...}, at: [<ffffffff839b3313>] spin_trylock
include/linux/spinlock.h:309 [inline]
#6: (slock-AF_INET){+.-...}, at: [<ffffffff839b3313>] icmp_xmit_lock
net/ipv4/icmp.c:219 [inline]
#6: (slock-AF_INET){+.-...}, at: [<ffffffff839b3313>]
icmp_send+0x803/0x1c80 net/ipv4/icmp.c:681
#7: (rcu_read_lock_bh){......}, at: [<ffffffff838ab9a1>]
ip_finish_output2+0x2c1/0x15a0 net/ipv4/ip_output.c:198
#8: (rcu_read_lock_bh){......}, at: [<ffffffff836d1dee>]
__dev_queue_xmit+0x23e/0x1e60 net/core/dev.c:3324
#9: (dev->qdisc_running_key ?: &qdisc_running_key){+.....}, at:
[<ffffffff836d3a27>] dev_queue_xmit+0x17/0x20 net/core/dev.c:3423

stack backtrace:
CPU: 0 PID: 12392 Comm: modprobe Not tainted 4.10.0+ #29
Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:16 [inline]
dump_stack+0x2ee/0x3ef lib/dump_stack.c:52
print_circular_bug+0x307/0x3b0 kernel/locking/lockdep.c:1204
check_prev_add kernel/locking/lockdep.c:1830 [inline]
check_prevs_add+0xa8f/0x19f0 kernel/locking/lockdep.c:1940
validate_chain kernel/locking/lockdep.c:2267 [inline]
__lock_acquire+0x2149/0x3430 kernel/locking/lockdep.c:3340
lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x33/0x50 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:299 [inline]
__netif_tx_lock include/linux/netdevice.h:3486 [inline]
sch_direct_xmit+0x282/0x6d0 net/sched/sch_generic.c:180
__dev_xmit_skb net/core/dev.c:3092 [inline]
__dev_queue_xmit+0x13e5/0x1e60 net/core/dev.c:3358
dev_queue_xmit+0x17/0x20 net/core/dev.c:3423
neigh_hh_output include/net/neighbour.h:468 [inline]
neigh_output include/net/neighbour.h:476 [inline]
ip_finish_output2+0xf6c/0x15a0 net/ipv4/ip_output.c:228
ip_finish_output+0xa29/0xe10 net/ipv4/ip_output.c:316
NF_HOOK_COND include/linux/netfilter.h:246 [inline]
ip_output+0x1f0/0x7a0 net/ipv4/ip_output.c:404
dst_output include/net/dst.h:486 [inline]
ip_local_out+0x95/0x170 net/ipv4/ip_output.c:124
ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1492
ip_push_pending_frames+0x64/0x80 net/ipv4/ip_output.c:1512
icmp_push_reply+0x372/0x4d0 net/ipv4/icmp.c:394
icmp_send+0x156c/0x1c80 net/ipv4/icmp.c:754
ip_expire+0x40e/0x6c0 net/ipv4/ip_fragment.c:239
call_timer_fn+0x241/0x820 kernel/time/timer.c:1268
expire_timers kernel/time/timer.c:1307 [inline]
__run_timers+0x960/0xcf0 kernel/time/timer.c:1601
run_timer_softirq+0x21/0x80 kernel/time/timer.c:1614
__do_softirq+0x31f/0xbe7 kernel/softirq.c:284
invoke_softirq kernel/softirq.c:364 [inline]
irq_exit+0x1cc/0x200 kernel/softirq.c:405
exiting_irq arch/x86/include/asm/apic.h:657 [inline]
smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:962
apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:707
RIP: 0010:__read_once_size include/linux/compiler.h:254 [inline]
RIP: 0010:atomic_read arch/x86/include/asm/atomic.h:26 [inline]
RIP: 0010:rcu_dynticks_curr_cpu_in_eqs kernel/rcu/tree.c:350 [inline]
RIP: 0010:__rcu_is_watching kernel/rcu/tree.c:1133 [inline]
RIP: 0010:rcu_is_watching+0x83/0x110 kernel/rcu/tree.c:1147
RSP: 0000:ffff8801c391f120 EFLAGS: 00000a03 ORIG_RAX: ffffffffffffff10
RAX: dffffc0000000000 RBX: ffff8801c391f148 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 000055edd4374000 RDI: ffff8801dbe1ae0c
RBP: ffff8801c391f1a0 R08: 0000000000000002 R09: 0000000000000000
R10: dffffc0000000000 R11: 0000000000000002 R12: 1ffff10038723e25
R13: ffff8801dbe1ae00 R14: ffff8801c391f680 R15: dffffc0000000000
</IRQ>
rcu_read_lock_held+0x87/0xc0 kernel/rcu/update.c:293
radix_tree_deref_slot include/linux/radix-tree.h:238 [inline]
filemap_map_pages+0x6d4/0x1570 mm/filemap.c:2335
do_fault_around mm/memory.c:3231 [inline]
do_read_fault mm/memory.c:3265 [inline]
do_fault+0xbd5/0x2080 mm/memory.c:3370
handle_pte_fault mm/memory.c:3600 [inline]
__handle_mm_fault+0x1062/0x2cb0 mm/memory.c:3714
handle_mm_fault+0x1e2/0x480 mm/memory.c:3751
__do_page_fault+0x4f6/0xb60 arch/x86/mm/fault.c:1397
do_page_fault+0x54/0x70 arch/x86/mm/fault.c:1460
page_fault+0x28/0x30 arch/x86/entry/entry_64.S:1011
RIP: 0033:0x7f83172f2786
RSP: 002b:00007fffe859ae80 EFLAGS: 00010293
RAX: 000055edd4373040 RBX: 00007f83175111c8 RCX: 000055edd4373238
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007f8317510970
RBP: 00007fffe859afd0 R08: 0000000000000009 R09: 0000000000000000
R10: 0000000000000064 R11: 0000000000000000 R12: 000055edd4373040
R13: 0000000000000000 R14: 00007fffe859afe8 R15: 0000000000000000

[Eric Dumazet]

This looks a false positive.
An ICMP message can not be possibly fragmented.

Following patch should fix the lockdep issue.

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index bbe7f72db9c157ba2d6c5292637c2f58ad39a123..b3cdeec85f1f2c612c362590e828f50596a5c247 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -198,6 +198,7 @@ static void ip_expire(unsigned long arg)
qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
net = container_of(qp->q.net, struct net, ipv4.frags);

+ rcu_read_lock();
spin_lock(&qp->q.lock);

if (qp->q.flags & INET_FRAG_COMPLETE)
@@ -207,7 +208,7 @@ static void ip_expire(unsigned long arg)
__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);

if (!inet_frag_evicting(&qp->q)) {
- struct sk_buff *head = qp->q.fragments;
+ struct sk_buff *clone, *head = qp->q.fragments;
const struct iphdr *iph;
int err;

@@ -216,32 +217,40 @@ static void ip_expire(unsigned long arg)
if (!(qp->q.flags & INET_FRAG_FIRST_IN) || !qp->q.fragments)
goto out;

- rcu_read_lock();
head->dev = dev_get_by_index_rcu(net, qp->iif);
if (!head->dev)
- goto out_rcu_unlock;
+ goto out;
+

/* skb has no dst, perform route lookup again */
iph = ip_hdr(head);
err = ip_route_input_noref(head, iph->daddr, iph->saddr,
iph->tos, head->dev);
if (err)
- goto out_rcu_unlock;
+ goto out;

/* Only an end host needs to send an ICMP
* "Fragment Reassembly Timeout" message, per RFC792.
*/
if (frag_expire_skip_icmp(qp->user) &&
(skb_rtable(head)->rt_type != RTN_LOCAL))
- goto out_rcu_unlock;
+ goto out;
+
+ clone = skb_clone(head, GFP_ATOMIC);

/* Send an ICMP "Fragment Reassembly Timeout" message. */
- icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
-out_rcu_unlock:
- rcu_read_unlock();
+ if (clone) {
+ spin_unlock(&qp->q.lock);
+ icmp_send(clone, ICMP_TIME_EXCEEDED,
+ ICMP_EXC_FRAGTIME, 0);
+ consume_skb(clone);
+ goto out_rcu_unlock;
+ }
}
out:
spin_unlock(&qp->q.lock);
+out_rcu_unlock:
+ rcu_read_unlock();
ipq_put(qp);
}

[Dmitry Vyukov]

I am confused. Lockdep has observed both of these stacks:

CPU0 CPU1
---- ----
lock(&(&q->lock)->rlock);
lock(_xmit_ETHER#2);
lock(&(&q->lock)->rlock);
lock(_xmit_ETHER#2);

So it somehow happened. Or what do you mean?

[Eric Dumazet]

On Tue, Mar 14, 2017 at 7:46 AM, Dmitry Vyukov <dvy...@google.com> wrote:

> I am confused. Lockdep has observed both of these stacks:
>
> CPU0 CPU1
> ---- ----
> lock(&(&q->lock)->rlock);
> lock(_xmit_ETHER#2);
> lock(&(&q->lock)->rlock);
> lock(_xmit_ETHER#2);
>
>
> So it somehow happened. Or what do you mean?
>

Lockdep said " possible circular locking dependency detected " .
It is not an actual deadlock, but lockdep machinery firing.

For a dead lock to happen, this would require that he ICMP message
sent by ip_expire() is itself fragmented and reassembled.
This cannot be, because ICMP messages are not candidates for
fragmentation, but lockdep can not know that of course...

[Dmitry Vyukov]

Ah, I see. Thanks.

[Paolo Abeni]

I'm wondering if we really need to keep the fragment queue lock held
while sending the icmp packet ? we hold a reference to the struct, so
it can't be deleted, and AFAICS after ipq_kill() nobody else could
access/modify that queue.

That lock is there pretty much forever, but perhaps is only a leftover
and we can release it just after ipq_kill() ?

Paolo

[Eric Dumazet]

On Tue, Mar 14, 2017 at 8:03 AM, Paolo Abeni <pab...@redhat.com> wrote:

> I'm wondering if we really need to keep the fragment queue lock held
> while sending the icmp packet ? we hold a reference to the struct, so
> it can't be deleted, and AFAICS after ipq_kill() nobody else could
> access/modify that queue.
>
> That lock is there pretty much forever, but perhaps is only a leftover
> and we can release it just after ipq_kill() ?

Maybe, but for peace of mind I would make sure this code path owns the
skb (head) before releasing the lock.

Seems something to try for net-next ?

[Paolo Abeni]

Agreed.

I asked because I was in doubt I missed something obvious.

Thank you,

Paolo

[Cong Wang]

It doesn't have to be ICMP, as long as get the same hash for
the inet_frag_queue, we will need to take the same lock and
deadlock will happen.

hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);

So it is really up to this hash function.

[Dmitry Vyukov]

Is the following the same issue?
It mentions dev->qdisc_tx_busylock, but I am not sure if it's relevant
if there already a cycle between _xmit_ETHER#2 -->
&(&q->lock)->rlock#2.


[ INFO: possible circular locking dependency detected ]
4.11.0-rc2+ #340 Not tainted
-------------------------------------------------------
swapper/1/0 is trying to acquire lock:
(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-...}, at:
[<ffffffff834cff12>] spin_lock include/linux/spinlock.h:299 [inline]
(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-...}, at:
[<ffffffff834cff12>] __dev_xmit_skb net/core/dev.c:3077 [inline]
(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-...}, at:
[<ffffffff834cff12>] __dev_queue_xmit+0x11b2/0x1ed0
net/core/dev.c:3359

but task is already holding lock:

(&(&q->lock)->rlock#2){+.-...}, at: [<ffffffff8368dc21>] spin_lock
include/linux/spinlock.h:299 [inline]
(&(&q->lock)->rlock#2){+.-...}, at: [<ffffffff8368dc21>]
ip_expire+0x51/0x6d0 net/ipv4/ip_fragment.c:201

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&(&q->lock)->rlock#2){+.-...}:
lock_acquire+0x217/0x5e0 kernel/locking/lockdep.c:3762

__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x33/0x50 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:299 [inline]

ip_defrag+0x395/0x4070 net/ipv4/ip_fragment.c:669
ip_check_defrag+0x4e7/0x890 net/ipv4/ip_fragment.c:713
packet_rcv_fanout+0x26b/0x7f0 net/packet/af_packet.c:1459
deliver_skb net/core/dev.c:1835 [inline]
dev_queue_xmit_nit+0x2a6/0xaa0 net/core/dev.c:1891
xmit_one net/core/dev.c:2904 [inline]
dev_hard_start_xmit+0x16b/0xb20 net/core/dev.c:2924
sch_direct_xmit+0x31d/0x6d0 net/sched/sch_generic.c:182
__dev_xmit_skb net/core/dev.c:3093 [inline]
__dev_queue_xmit+0x166a/0x1ed0 net/core/dev.c:3359
dev_queue_xmit+0x17/0x20 net/core/dev.c:3424

neigh_hh_output include/net/neighbour.h:468 [inline]
neigh_output include/net/neighbour.h:476 [inline]

ip_finish_output2+0xe91/0x13f0 net/ipv4/ip_output.c:228
ip_do_fragment+0x1d17/0x25f0 net/ipv4/ip_output.c:672
ip_fragment.constprop.53+0x145/0x200 net/ipv4/ip_output.c:545
ip_finish_output+0x5c1/0xb40 net/ipv4/ip_output.c:314
NF_HOOK_COND include/linux/netfilter.h:246 [inline]
ip_output+0x1d0/0x870 net/ipv4/ip_output.c:404

dst_output include/net/dst.h:486 [inline]
ip_local_out+0x95/0x170 net/ipv4/ip_output.c:124
ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1492
ip_push_pending_frames+0x64/0x80 net/ipv4/ip_output.c:1512

raw_sendmsg+0x25e9/0x3870 net/ipv4/raw.c:655
inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:762

sock_sendmsg_nosec net/socket.c:633 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:643

___sys_sendmsg+0x35e/0x860 net/socket.c:1986
__sys_sendmmsg+0x1e6/0x5f0 net/socket.c:2076
SYSC_sendmmsg net/socket.c:2107 [inline]
SyS_sendmmsg+0x35/0x60 net/socket.c:2102
do_syscall_64+0x26c/0x810 arch/x86/entry/common.c:281
return_from_SYSCALL_64+0x0/0x7a

-> #1 (_xmit_ETHER#2){+.-...}:
lock_acquire+0x217/0x5e0 kernel/locking/lockdep.c:3762

__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x33/0x50 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:299 [inline]
__netif_tx_lock include/linux/netdevice.h:3486 [inline]

sch_direct_xmit+0x280/0x6d0 net/sched/sch_generic.c:180
__dev_xmit_skb net/core/dev.c:3093 [inline]
__dev_queue_xmit+0x166a/0x1ed0 net/core/dev.c:3359
dev_queue_xmit+0x17/0x20 net/core/dev.c:3424

neigh_hh_output include/net/neighbour.h:468 [inline]
neigh_output include/net/neighbour.h:476 [inline]

ip6_finish_output2+0x1421/0x2270 net/ipv6/ip6_output.c:123
ip6_fragment+0x2c6c/0x3920 net/ipv6/ip6_output.c:724
ip6_finish_output+0x319/0x950 net/ipv6/ip6_output.c:147
NF_HOOK_COND include/linux/netfilter.h:246 [inline]
ip6_output+0x1b6/0x890 net/ipv6/ip6_output.c:163
dst_output include/net/dst.h:486 [inline]
ip6_local_out+0x95/0x170 net/ipv6/output_core.c:172
ip6_send_skb+0xa1/0x340 net/ipv6/ip6_output.c:1739
ip6_push_pending_frames+0xb3/0xe0 net/ipv6/ip6_output.c:1759
rawv6_push_pending_frames net/ipv6/raw.c:613 [inline]
rawv6_sendmsg+0x2d7c/0x3ee0 net/ipv6/raw.c:930
inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:762

sock_sendmsg_nosec net/socket.c:633 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:643

___sys_sendmsg+0x738/0x860 net/socket.c:1986
__sys_sendmsg+0xe5/0x210 net/socket.c:2020
SYSC_sendmsg net/socket.c:2031 [inline]
SyS_sendmsg+0x2d/0x50 net/socket.c:2027
entry_SYSCALL_64_fastpath+0x1f/0xc2

-> #0 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-...}:
check_prev_add kernel/locking/lockdep.c:1830 [inline]
check_prevs_add kernel/locking/lockdep.c:1940 [inline]
validate_chain kernel/locking/lockdep.c:2267 [inline]
__lock_acquire+0x2f07/0x3a80 kernel/locking/lockdep.c:3347
lock_acquire+0x217/0x5e0 kernel/locking/lockdep.c:3762

__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x33/0x50 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:299 [inline]

__dev_xmit_skb net/core/dev.c:3077 [inline]
__dev_queue_xmit+0x11b2/0x1ed0 net/core/dev.c:3359
dev_queue_xmit+0x17/0x20 net/core/dev.c:3424

neigh_hh_output include/net/neighbour.h:468 [inline]
neigh_output include/net/neighbour.h:476 [inline]

ip_finish_output2+0xe91/0x13f0 net/ipv4/ip_output.c:228
ip_finish_output+0x7a3/0xb40 net/ipv4/ip_output.c:316
NF_HOOK_COND include/linux/netfilter.h:246 [inline]
ip_output+0x1d0/0x870 net/ipv4/ip_output.c:404

dst_output include/net/dst.h:486 [inline]
ip_local_out+0x95/0x170 net/ipv4/ip_output.c:124
ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1492
ip_push_pending_frames+0x64/0x80 net/ipv4/ip_output.c:1512

icmp_push_reply+0x372/0x4c0 net/ipv4/icmp.c:394
icmp_send+0x12f5/0x1920 net/ipv4/icmp.c:754
ip_expire+0x420/0x6d0 net/ipv4/ip_fragment.c:239
call_timer_fn+0x254/0x940 kernel/time/timer.c:1268
expire_timers kernel/time/timer.c:1307 [inline]
__run_timers+0x716/0xbb0 kernel/time/timer.c:1601
run_timer_softirq+0x21/0x80 kernel/time/timer.c:1614
__do_softirq+0x2fc/0xbf6 kernel/softirq.c:284

invoke_softirq kernel/softirq.c:364 [inline]
irq_exit+0x1cc/0x200 kernel/softirq.c:405
exiting_irq arch/x86/include/asm/apic.h:657 [inline]
smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:962

apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:487
native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
arch_safe_halt arch/x86/include/asm/paravirt.h:98 [inline]
default_idle+0xba/0x480 arch/x86/kernel/process.c:275
arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:266
default_idle_call+0x44/0xa0 kernel/sched/idle.c:97
cpuidle_idle_call kernel/sched/idle.c:155 [inline]
do_idle+0x296/0x410 kernel/sched/idle.c:244
cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:346
start_secondary+0x2a7/0x340 arch/x86/kernel/smpboot.c:275
verify_cpu+0x0/0xfc

other info that might help us debug this:

Chain exists of:
dev->qdisc_tx_busylock ?: &qdisc_tx_busylock --> _xmit_ETHER#2 -->
&(&q->lock)->rlock#2

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&(&q->lock)->rlock#2);
lock(_xmit_ETHER#2);
lock(&(&q->lock)->rlock#2);
lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);

*** DEADLOCK ***

6 locks held by swapper/1/0:
#0: (((&q->timer))){+.-...}, at: [<ffffffff815d9716>]
lockdep_copy_map include/linux/lockdep.h:175 [inline]
#0: (((&q->timer))){+.-...}, at: [<ffffffff815d9716>]
call_timer_fn+0x1c6/0x940 kernel/time/timer.c:1258
#1: (&(&q->lock)->rlock#2){+.-...}, at: [<ffffffff8368dc21>]
spin_lock include/linux/spinlock.h:299 [inline]
#1: (&(&q->lock)->rlock#2){+.-...}, at: [<ffffffff8368dc21>]
ip_expire+0x51/0x6d0 net/ipv4/ip_fragment.c:201
#2: (rcu_read_lock){......}, at: [<ffffffff8368dd95>]
ip_expire+0x1c5/0x6d0 net/ipv4/ip_fragment.c:216
#3: (k-slock-AF_INET){+.-...}, at: [<ffffffff83797f54>] spin_trylock
include/linux/spinlock.h:309 [inline]
#3: (k-slock-AF_INET){+.-...}, at: [<ffffffff83797f54>]
icmp_xmit_lock net/ipv4/icmp.c:219 [inline]
#3: (k-slock-AF_INET){+.-...}, at: [<ffffffff83797f54>]
icmp_send+0x6e4/0x1920 net/ipv4/icmp.c:681
#4: (rcu_read_lock_bh){......}, at: [<ffffffff8369e5ed>]
ip_finish_output2+0x22d/0x13f0 net/ipv4/ip_output.c:198
#5: (rcu_read_lock_bh){......}, at: [<ffffffff834cefb4>]
__dev_queue_xmit+0x254/0x1ed0 net/core/dev.c:3325

stack backtrace:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.11.0-rc2+ #340
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011

Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:16 [inline]

dump_stack+0x1b8/0x28d lib/dump_stack.c:52
print_circular_bug+0x358/0x400 kernel/locking/lockdep.c:1204
check_prev_add kernel/locking/lockdep.c:1830 [inline]
check_prevs_add kernel/locking/lockdep.c:1940 [inline]
validate_chain kernel/locking/lockdep.c:2267 [inline]
__lock_acquire+0x2f07/0x3a80 kernel/locking/lockdep.c:3347
lock_acquire+0x217/0x5e0 kernel/locking/lockdep.c:3762

__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x33/0x50 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:299 [inline]

__dev_xmit_skb net/core/dev.c:3077 [inline]
__dev_queue_xmit+0x11b2/0x1ed0 net/core/dev.c:3359
dev_queue_xmit+0x17/0x20 net/core/dev.c:3424

neigh_hh_output include/net/neighbour.h:468 [inline]
neigh_output include/net/neighbour.h:476 [inline]

ip_finish_output2+0xe91/0x13f0 net/ipv4/ip_output.c:228
ip_finish_output+0x7a3/0xb40 net/ipv4/ip_output.c:316
NF_HOOK_COND include/linux/netfilter.h:246 [inline]
ip_output+0x1d0/0x870 net/ipv4/ip_output.c:404

dst_output include/net/dst.h:486 [inline]
ip_local_out+0x95/0x170 net/ipv4/ip_output.c:124
ip_send_skb+0x3c/0xc0 net/ipv4/ip_output.c:1492
ip_push_pending_frames+0x64/0x80 net/ipv4/ip_output.c:1512

icmp_push_reply+0x372/0x4c0 net/ipv4/icmp.c:394
icmp_send+0x12f5/0x1920 net/ipv4/icmp.c:754
ip_expire+0x420/0x6d0 net/ipv4/ip_fragment.c:239
call_timer_fn+0x254/0x940 kernel/time/timer.c:1268
expire_timers kernel/time/timer.c:1307 [inline]
__run_timers+0x716/0xbb0 kernel/time/timer.c:1601
run_timer_softirq+0x21/0x80 kernel/time/timer.c:1614
__do_softirq+0x2fc/0xbf6 kernel/softirq.c:284

invoke_softirq kernel/softirq.c:364 [inline]
irq_exit+0x1cc/0x200 kernel/softirq.c:405
exiting_irq arch/x86/include/asm/apic.h:657 [inline]
smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:962

apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:487
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
RSP: 0018:ffff88003e027db0 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff10
RAX: dffffc0000000000 RBX: 1ffff10007c04fb9 RCX: 0000000000000000
RDX: 1ffffffff09d8ed4 RSI: 0000000000000001 RDI: ffffffff84ec76a0
RBP: ffff88003e027db0 R08: ffffed0007c03461 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff84ec7690
R13: ffff88003e027e68 R14: 0000000000000000 R15: 0000000000000001
</IRQ>
arch_safe_halt arch/x86/include/asm/paravirt.h:98 [inline]
default_idle+0xba/0x480 arch/x86/kernel/process.c:275
arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:266
default_idle_call+0x44/0xa0 kernel/sched/idle.c:97
cpuidle_idle_call kernel/sched/idle.c:155 [inline]
do_idle+0x296/0x410 kernel/sched/idle.c:244
cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:346
start_secondary+0x2a7/0x340 arch/x86/kernel/smpboot.c:275
start_cpu+0x14/0x14 arch/x86/kernel/head_64.S:306

[Eric Dumazet]

False positive again.

veth needs to use netdev_lockdep_set_classes(), assuming you use veth ?

I will provide a patch, thanks.

cf515802043cccecfe9ab75065f8fc71e6ec9bab missed a few drivers.