============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.6.1501/8826 is trying to acquire lock:
ffff8880608e7218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
ffff8880608e7218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3922 [inline]
ffff8880608e7218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_queue_xmit+0x1fd1/0x2f80 net/core/dev.c:4266
but task is already holding lock:
ffff888018199258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: spin_trylock include/linux/spinlock.h:374 [inline]
ffff888018199258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline]
ffff888018199258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3884 [inline]
ffff888018199258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_queue_xmit+0x1120/0x2f80 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
9 locks held by syz.6.1501/8826:
#0: ffff88806221d9d8 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#0: ffff88806221d9d8 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: zap_pte_range mm/memory.c:1342 [inline]
#0: ffff88806221d9d8 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: zap_pmd_range mm/memory.c:1505 [inline]
#0: ffff88806221d9d8 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: zap_pud_range mm/memory.c:1534 [inline]
#0: ffff88806221d9d8 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: zap_p4d_range mm/memory.c:1555 [inline]
#0: ffff88806221d9d8 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: unmap_page_range+0x94a/0x2500 mm/memory.c:1576
#1: ffffc90000dd0be0 ((&ndev->rs_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline]
#1: ffffc90000dd0be0 ((&ndev->rs_timer)){+.-.}-{0:0}, at: call_timer_fn+0xca/0x540 kernel/time/timer.c:1638
#2: ffffffff8c31eb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
#3: ffffffff8c31eb80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#4: ffffffff8c31eb80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#5: ffff888018199258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: spin_trylock include/linux/spinlock.h:374 [inline]
#5: ffff888018199258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline]
#5: ffff888018199258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3884 [inline]
#5: ffff888018199258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_queue_xmit+0x1120/0x2f80 net/core/dev.c:4266
#6: ffffffff8c31eb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#7: ffffffff8c31eb80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#8: ffffffff8c31eb80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
stack backtrace:
CPU: 1 PID: 8826 Comm: syz.6.1501 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
__lock_acquire+0x1236/0x7d10 kernel/locking/lockdep.c:-1
lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
__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+0x1fd1/0x2f80 net/core/dev.c:4266
neigh_hh_output include/net/neighbour.h:493 [inline]
neigh_output include/net/neighbour.h:507 [inline]
ip_finish_output2+0xc87/0x10a0 net/ipv4/ip_output.c:228
NF_HOOK_COND include/linux/netfilter.h:291 [inline]
ip_output+0x2c0/0x3e0 net/ipv4/ip_output.c:434
iptunnel_xmit+0x4d6/0x8e0 net/ipv4/ip_tunnel_core.c:82
ip_tunnel_xmit+0x1905/0x2280 net/ipv4/ip_tunnel.c:824
__gre_xmit net/ipv4/ip_gre.c:474 [inline]
gre_tap_xmit+0x4f9/0x6e0 net/ipv4/ip_gre.c:751
__netdev_start_xmit include/linux/netdevice.h:5036 [inline]
netdev_start_xmit include/linux/netdevice.h:5050 [inline]
xmit_one net/core/dev.c:3662 [inline]
dev_hard_start_xmit+0x2a5/0x7e0 net/core/dev.c:3678
sch_direct_xmit+0x25a/0x4b0 net/sched/sch_generic.c:345
__dev_xmit_skb net/core/dev.c:3897 [inline]
__dev_queue_xmit+0x179f/0x2f80 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+0x1051/0x1510 net/ipv6/ip6_output.c:130
dst_output include/net/dst.h:452 [inline]
NF_HOOK include/linux/netfilter.h:302 [inline]
ndisc_send_skb+0xc2a/0x1500 net/ipv6/ndisc.c:513
addrconf_rs_timer+0x2d1/0x630 net/ipv6/addrconf.c:3956
call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
expire_timers kernel/time/timer.c:1699 [inline]
__run_timers+0x53e/0x800 kernel/time/timer.c:1970
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
handle_softirqs+0x339/0x830 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_release+0x5a4/0x8a0 kernel/locking/lockdep.c:5647
Code: 80 00 00 00 f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 2c 04 f8 75 6f 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 2c 00 00 00 00 43 c7 44 2c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc900033e7440 EFLAGS: 00000206
RAX: 0000000000000001 RBX: e668264dc84383e6 RCX: 88597b8cadff2600
RDX: 0000000000000001 RSI: ffffffff8a2b3aa0 RDI: ffffffff8a79fe40
RBP: ffffc900033e7550 R08: ffffffff8d89f06f R09: 1ffffffff1b13e0d
R10: dffffc0000000000 R11: fffffbfff1b13e0e R12: 1ffff9200067ce94
R13: dffffc0000000000 R14: ffff888076c4e420 R15: 0000000000000246
zap_pte_range mm/memory.c:1384 [inline]
zap_pmd_range mm/memory.c:1505 [inline]
zap_pud_range mm/memory.c:1534 [inline]
zap_p4d_range mm/memory.c:1555 [inline]
unmap_page_range+0xf96/0x2500 mm/memory.c:1576
unmap_vmas+0x131/0x250 mm/memory.c:1653
exit_mmap+0x3b9/0x640 mm/mmap.c:3216
__mmput+0x115/0x3b0 kernel/fork.c:1127
exit_mm+0x588/0x6e0 kernel/exit.c:550
do_exit+0x5a9/0x20c0 kernel/exit.c:870
do_group_exit+0x12e/0x300 kernel/exit.c:997
get_signal+0x6ca/0x12c0 kernel/signal.c:2900
arch_do_signal_or_restart+0xe7/0x12c0 arch/x86/kernel/signal.c:867
handle_signal_work kernel/entry/common.c:154 [inline]
exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f21881cfdd9
Code: Unable to access opcode bytes at RIP 0x7f21881cfdaf.
RSP: 002b:00007f21864290e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f2188448fa8 RCX: 00007f21881cfdd9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f2188448fa8
RBP: 00007f2188448fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2188449038 R14: 00007ffcecaa6e40 R15: 00007ffcecaa6f28
----------------
Code disassembly (best guess):
0: 80 00 00 addb $0x0,(%rax)
3: 00 f7 add %dh,%bh
5: 84 24 80 test %ah,(%rax,%rax,4)
8: 00 00 add %al,(%rax)
a: 00 00 add %al,(%rax)
c: 02 00 add (%rax),%al
e: 00 43 c6 add %al,-0x3a(%rbx)
11: 44 2c 04 rex.R sub $0x4,%al
14: f8 clc
15: 75 6f jne 0x86
17: 41 f7 c7 00 02 00 00 test $0x200,%r15d
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 04 2c 00 00 00 movq $0x0,(%r12,%r13,1) <-- trapping instruction
31: 00
32: 43 c7 44 2c 08 00 00 movl $0x0,0x8(%r12,%r13,1)
39: 00 00
3b: 65 gs
3c: 48 rex.W
3d: 8b .byte 0x8b
3e: 04 25 add $0x25,%al