============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.3.4508/16091 is trying to acquire lock:
ffff88802bc8fa18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
ffff88802bc8fa18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3922 [inline]
ffff88802bc8fa18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_queue_xmit+0x1e69/0x2e50 net/core/dev.c:4266
but task is already holding lock:
ffff88807aff0258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: spin_trylock include/linux/spinlock.h:374 [inline]
ffff88807aff0258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:174 [inline]
ffff88807aff0258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3884 [inline]
ffff88807aff0258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_queue_xmit+0x108d/0x2e50 net/core/dev.c:4266
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);
lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);
*** DEADLOCK ***
May be due to missing lock nesting notation
13 locks held by syz.3.4508/16091:
#0: ffff888053797828 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:136 [inline]
#0: ffff888053797828 (&mm->mmap_lock){++++}-{3:3}, at: do_user_addr_fault+0x2bb/0xc90 arch/x86/mm/fault.c:1296
#1: ffffffff8c31ef60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
#2: ffffffff8c31ef60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
#3: ffffc90000dd0bc0 ((&ndev->rs_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline]
#3: ffffc90000dd0bc0 ((&ndev->rs_timer)){+.-.}-{0:0}, at: call_timer_fn+0xca/0x540 kernel/time/timer.c:1638
#4: ffffffff8c31ef60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
#5: ffffffff8c31efc0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#6: ffffffff8c31efc0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#7: ffff88807aff0258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: spin_trylock include/linux/spinlock.h:374 [inline]
#7: ffff88807aff0258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:174 [inline]
#7: ffff88807aff0258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3884 [inline]
#7: ffff88807aff0258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_queue_xmit+0x108d/0x2e50 net/core/dev.c:4266
#8: ffff88807650d060 (k-slock-AF_INET6){+.-.}-{2:2}, at: spin_trylock include/linux/spinlock.h:374 [inline]
#8: ffff88807650d060 (k-slock-AF_INET6){+.-.}-{2:2}, at: icmpv6_xmit_lock net/ipv6/icmp.c:118 [inline]
#8: ffff88807650d060 (k-slock-AF_INET6){+.-.}-{2:2}, at: icmp6_send+0xbe5/0x19a0 net/ipv6/icmp.c:551
#9: ffffffff8c31ef60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
#10: ffffffff8c31ef60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#11: ffffffff8c31efc0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#12: ffffffff8c31efc0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
stack backtrace:
CPU: 1 PID: 16091 Comm: syz.3.4508 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
__lock_acquire+0x1247/0x7b50 kernel/locking/lockdep.c:-1
lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5625
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:364 [inline]
__dev_xmit_skb net/core/dev.c:3922 [inline]
__dev_queue_xmit+0x1e69/0x2e50 net/core/dev.c:4266
neigh_hh_output include/net/neighbour.h:493 [inline]
neigh_output include/net/neighbour.h:507 [inline]
ip6_finish_output2+0x1134/0x1640 net/ipv6/ip6_output.c:132
ip6_send_skb+0x1af/0x350 net/ipv6/ip6_output.c:1886
icmp6_send+0x134a/0x19a0 net/ipv6/icmp.c:630
__icmpv6_send include/linux/icmpv6.h:28 [inline]
icmpv6_send include/linux/icmpv6.h:49 [inline]
ip6_pkt_drop+0x55a/0x690 net/ipv6/route.c:4535
ip6_pkt_discard_out+0xee/0x110 net/ipv6/route.c:4548
ip6tunnel_xmit+0x1ac/0x3d0 include/net/ip6_tunnel.h:160
ip6_tnl_xmit+0x1b65/0x2260 net/ipv6/ip6_tunnel.c:1267
__gre6_xmit+0x960/0xc70 net/ipv6/ip6_gre.c:787
ip6gre_xmit_ipv6 net/ipv6/ip6_gre.c:843 [inline]
ip6gre_tunnel_xmit+0xcad/0x1080 net/ipv6/ip6_gre.c:895
__netdev_start_xmit include/linux/netdevice.h:5049 [inline]
netdev_start_xmit include/linux/netdevice.h:5063 [inline]
xmit_one net/core/dev.c:3662 [inline]
dev_hard_start_xmit+0x297/0x7d0 net/core/dev.c:3678
sch_direct_xmit+0x24d/0x4a0 net/sched/sch_generic.c:345
__dev_xmit_skb net/core/dev.c:3897 [inline]
__dev_queue_xmit+0x1694/0x2e50 net/core/dev.c:4266
neigh_hh_output include/net/neighbour.h:493 [inline]
neigh_output include/net/neighbour.h:507 [inline]
ip6_finish_output2+0x1134/0x1640 net/ipv6/ip6_output.c:132
dst_output include/net/dst.h:452 [inline]
NF_HOOK include/linux/netfilter.h:302 [inline]
ndisc_send_skb+0xb7c/0x1410 net/ipv6/ndisc.c:513
addrconf_rs_timer+0x367/0x640 net/ipv6/addrconf.c:3966
call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
expire_timers kernel/time/timer.c:1699 [inline]
__run_timers+0x56c/0x810 kernel/time/timer.c:1970
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
handle_softirqs+0x336/0x830 kernel/softirq.c:576
__do_softirq kernel/softirq.c:610 [inline]
invoke_softirq kernel/softirq.c:450 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:lock_acquire+0x208/0x400 kernel/locking/lockdep.c:5629
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3d 04 f8 0f 85 f1 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 43 c7 44 3d 08 00 00 00 00 65 48 8b 04
RSP: 0000:ffffc9000303f840 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ba6c6498ffd5bc00
RDX: 0000000000000000 RSI: ffffffff8a2b3e80 RDI: ffffffff8a7a48c0
RBP: ffffc9000303f950 R08: dffffc0000000000 R09: 1ffffffff203e218
R10: dffffc0000000000 R11: fffffbfff203e219 R12: ffffffff8c31ef60
R13: 1ffff92000607f14 R14: 0000000000000246 R15: dffffc0000000000
rcu_lock_acquire+0x20/0x30 include/linux/rcupdate.h:313
rcu_read_lock include/linux/rcupdate.h:740 [inline]
percpu_ref_tryget_many include/linux/percpu-refcount.h:241 [inline]
percpu_ref_tryget+0x12/0x150 include/linux/percpu-refcount.h:266
css_tryget include/linux/cgroup.h:355 [inline]
get_mem_cgroup_from_objcg+0xa4/0x120 mm/memcontrol.c:2815
obj_cgroup_charge_pages+0x76/0x190 mm/memcontrol.c:3016
__memcg_kmem_charge_page+0x2fe/0x380 mm/memcontrol.c:3058
__alloc_pages+0x222/0x480 mm/page_alloc.c:5518
pmd_alloc_one include/asm-generic/pgalloc.h:126 [inline]
__pmd_alloc+0xa6/0x750 mm/memory.c:4958
pmd_alloc include/linux/mm.h:2191 [inline]
__handle_mm_fault mm/memory.c:4747 [inline]
handle_mm_fault+0xbd3/0x4440 mm/memory.c:4883
do_user_addr_fault+0x494/0xc90 arch/x86/mm/fault.c:1355
handle_page_fault arch/x86/mm/fault.c:1443 [inline]
exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1496
asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0033:0x7ff471d93aa3
Code: 80 00 00 00 8b b4 24 c0 00 00 00 89 30 e9 a0 fa ff ff 48 89 c2 48 8d 35 14 a3 1c 00 48 8d 3d ca a3 1c 00 31 c0 e8 5d 79 fe ff <89> 32 e9 58 ef ff ff 48 8d 05 57 4c 37 00 48 8d 3d 68 9c ee 00 c6
RSP: 002b:00007ffd2677edb0 EFLAGS: 00010246
RAX: 00000000005ffde8 RBX: 0000000000000000 RCX: 0000001b32364000
RDX: 0000001b32324000 RSI: 0000000000600000 RDI: 00007ff472108708
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 00007ffd2677f040
vkms_vblank_simulate: vblank timer overrun
GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog
----------------
Code disassembly (best guess):
0: f7 84 24 80 00 00 00 testl $0x200,0x80(%rsp)
7: 00 02 00 00
b: 43 c6 44 3d 04 f8 movb $0xf8,0x4(%r13,%r15,1)
11: 0f 85 f1 00 00 00 jne 0x108
17: 41 f7 c6 00 02 00 00 test $0x200,%r14d
1e: 74 01 je 0x21
20: fb sti
21: 48 c7 44 24 60 0e 36 movq $0x45e0360e,0x60(%rsp)
28: e0 45
* 2a: 4b c7 44 3d 00 00 00 movq $0x0,0x0(%r13,%r15,1) <-- trapping instruction
31: 00 00
33: 43 c7 44 3d 08 00 00 movl $0x0,0x8(%r13,%r15,1)
3a: 00 00
3c: 65 gs
3d: 48 rex.W
3e: 8b .byte 0x8b
3f: 04 .byte 0x4