=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
net/sched/sch_api.c:304 suspicious rcu_dereference_protected() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
6 locks held by syz.2.1288/9194:
#0: ffffc90000dd0be0 ((&d->timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline]
#0: ffffc90000dd0be0 ((&d->timer)){+.-.}-{0:0}, at: call_timer_fn+0xca/0x540 kernel/time/timer.c:1638
#1: ffffffff8c31eb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
#2: ffffffff8c31eb80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#3: ffff888078368108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#3: ffff888078368108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3924 [inline]
#3: ffff888078368108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xa2a/0x2f80 net/core/dev.c:4266
#4: ffff888078368148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: tipc_l2_send_msg+0x30a/0x3c0 net/tipc/bearer.c:518
#5: ffffffff8c31eb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
stack backtrace:
CPU: 1 PID: 9194 Comm: syz.2.1288 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
qdisc_lookup+0xa6/0x650 net/sched/sch_api.c:304
qdisc_tree_reduce_backlog+0x190/0x430 net/sched/sch_api.c:783
cake_dequeue+0x1bd6/0x4b10 net/sched/sch_cake.c:2205
netem_dequeue+0x12d2/0x1410 net/sched/sch_netem.c:766
dequeue_skb net/sched/sch_generic.c:295 [inline]
qdisc_restart net/sched/sch_generic.c:400 [inline]
__qdisc_run+0x236/0x1490 net/sched/sch_generic.c:418
__dev_xmit_skb net/core/dev.c:3955 [inline]
__dev_queue_xmit+0xe3d/0x2f80 net/core/dev.c:4266
tipc_l2_send_msg+0x30a/0x3c0 net/tipc/bearer.c:518
tipc_bearer_xmit_skb+0x292/0x3c0 net/tipc/bearer.c:577
tipc_disc_timeout+0x57d/0x6d0 net/tipc/discover.c:338
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:finish_lock_switch+0x134/0x280 kernel/sched/core.c:4804
Code: be ff ff ff ff e8 3c 62 68 08 85 c0 74 4a 4d 85 ff 75 66 0f 1f 44 00 00 48 89 df e8 e6 cd 71 08 e8 61 e6 2a 00 fb 48 83 c4 08 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 48 89 df e8 c9 09 fe ff 43 80 3c
RSP: 0018:ffffc9000329f2c8 EFLAGS: 00000282
RAX: 6978eae3d22f2d00 RBX: ffff8880b913a340 RCX: 6978eae3d22f2d00
RDX: dffffc0000000000 RSI: ffffffff8a2b2800 RDI: ffffffff8a79fe40
RBP: 1ffff11017227613 R08: ffff8880b913a343 R09: 1ffff11017227468
R10: dffffc0000000000 R11: ffffed1017227469 R12: 1ffff110172275c1
R13: dffffc0000000000 R14: ffff8880b913ae08 R15: 0000000000000000
finish_task_switch+0x12f/0x640 kernel/sched/core.c:4921
context_switch kernel/sched/core.c:5052 [inline]
__schedule+0x11f7/0x43c0 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_timeout+0xbd/0x2d0 kernel/time/timer.c:2093
unix_wait_for_peer+0x1f2/0x2e0 net/unix/af_unix.c:1315
unix_dgram_sendmsg+0x1083/0x18a0 net/unix/af_unix.c:1910
sock_sendmsg_nosec net/socket.c:706 [inline]
__sock_sendmsg net/socket.c:718 [inline]
____sys_sendmsg+0x5b7/0x8f0 net/socket.c:2445
___sys_sendmsg+0x236/0x2e0 net/socket.c:2499
__sys_sendmmsg+0x2ba/0x500 net/socket.c:2585
__do_sys_sendmmsg net/socket.c:2614 [inline]
__se_sys_sendmmsg net/socket.c:2611 [inline]
__x64_sys_sendmmsg+0x9c/0xb0 net/socket.c:2611
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f2b311d9dd9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2b2f433028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f2b31452fa0 RCX: 00007f2b311d9dd9
RDX: 0000000000000318 RSI: 00002000000bd000 RDI: 0000000000000004
RBP: 00007f2b3126fd69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2b31453038 R14: 00007f2b31452fa0 R15: 00007ffeffbc8f68
----------------
Code disassembly (best guess):
0: be ff ff ff ff mov $0xffffffff,%esi
5: e8 3c 62 68 08 call 0x8686246
a: 85 c0 test %eax,%eax
c: 74 4a je 0x58
e: 4d 85 ff test %r15,%r15
11: 75 66 jne 0x79
13: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
18: 48 89 df mov %rbx,%rdi
1b: e8 e6 cd 71 08 call 0x871ce06
20: e8 61 e6 2a 00 call 0x2ae686
25: fb sti
26: 48 83 c4 08 add $0x8,%rsp
* 2a: 5b pop %rbx <-- trapping instruction
2b: 41 5c pop %r12
2d: 41 5d pop %r13
2f: 41 5e pop %r14
31: 41 5f pop %r15
33: 5d pop %rbp
34: c3 ret
35: 48 89 df mov %rbx,%rdi
38: e8 c9 09 fe ff call 0xfffe0a06
3d: 43 rex.XB
3e: 80 .byte 0x80
3f: 3c .byte 0x3c