=============================
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.6.895/7823:
 #0: ffffc90000007bc0 ((&d->timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline]
 #0: ffffc90000007bc0 ((&d->timer)){+.-.}-{0:0}, at: call_timer_fn+0xca/0x540 kernel/time/timer.c:1638
 #1: ffffffff8d11efa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
 #2: ffffffff8d11f000 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
 #3: ffff88807b8ae108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
 #3: ffff88807b8ae108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3925 [inline]
 #3: ffff88807b8ae108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xa2b/0x2e50 net/core/dev.c:4267
 #4: ffff88807b8ae148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: tipc_l2_send_msg+0x2eb/0x3a0 net/tipc/bearer.c:519
 #5: ffffffff8d11efa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312

stack backtrace:
CPU: 0 PID: 7823 Comm: syz.6.895 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 qdisc_lookup+0xa6/0x640 net/sched/sch_api.c:304
 qdisc_tree_reduce_backlog+0x188/0x480 net/sched/sch_api.c:800
 cake_dequeue+0x1ddf/0x4a50 net/sched/sch_cake.c:2201
 netem_dequeue+0x12d3/0x1410 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+0x22f/0x14b0 net/sched/sch_generic.c:418
 __dev_xmit_skb net/core/dev.c:3956 [inline]
 __dev_queue_xmit+0xdce/0x2e50 net/core/dev.c:4267
 tipc_l2_send_msg+0x2eb/0x3a0 net/tipc/bearer.c:519
 tipc_bearer_xmit_skb+0x292/0x3c0 net/tipc/bearer.c:578
 tipc_disc_timeout+0x5e1/0x740 net/tipc/discover.c:340
 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
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__sanitizer_cov_trace_pc+0x41/0x60 kernel/kcov.c:210
Code: ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 34 16 00 00 00 74 2c 8b 91 10 16 00 00 83 fa 02 75 21 48 8b 91 18 16 00 00 48 8b 32 <48> 8d 7e 01 8b 89 14 16 00 00 48 39 cf 73 08 48 89 44 f2 08 48 89
RSP: 0000:ffffc9000529f6b8 EFLAGS: 00000246
RAX: ffffffff87fb255e RBX: ffffffff8d11efa0 RCX: ffff88802382bb80
RDX: ffffc90016061000 RSI: 0000000000066e82 RDI: 0000000000066e82
RBP: ffffc9000529f770 R08: ffff88802382bb87 R09: 1ffff11004705770
R10: dffffc0000000000 R11: ffffed1004705771 R12: 0000000000000000
R13: 0000000000000001 R14: dffffc0000000000 R15: ffff88807cd71800
 rcu_lock_acquire+0xe/0x30 include/linux/rcupdate.h:313
 rcu_read_lock include/linux/rcupdate.h:740 [inline]
 sk_filter_trim_cap+0x14e/0x7d0 net/core/filter.c:146
 sk_filter include/linux/filter.h:935 [inline]
 unix_dgram_sendmsg+0xbcd/0x19c0 net/unix/af_unix.c:1840
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 ____sys_sendmsg+0x5be/0x8f0 net/socket.c:2446
 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2500
 __sys_sendmmsg+0x2ba/0x500 net/socket.c:2586
 __do_sys_sendmmsg net/socket.c:2615 [inline]
 __se_sys_sendmmsg net/socket.c:2612 [inline]
 __x64_sys_sendmmsg+0x9c/0xb0 net/socket.c:2612
 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: 0033:0x7fc77e38bb19
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:00007fc77c5e2028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007fc77e611fa0 RCX: 00007fc77e38bb19
RDX: 0000000000000651 RSI: 0000200000000600 RDI: 0000000000000005
RBP: 00007fc77e423b70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc77e612038 R14: 00007fc77e611fa0 R15: 00007fffe1864688
 </TASK>
----------------
Code disassembly (best guess):
   0:	ff 00                	incl   (%rax)
   2:	74 11                	je     0x15
   4:	81 fa 00 01 00 00    	cmp    $0x100,%edx
   a:	75 35                	jne    0x41
   c:	83 b9 34 16 00 00 00 	cmpl   $0x0,0x1634(%rcx)
  13:	74 2c                	je     0x41
  15:	8b 91 10 16 00 00    	mov    0x1610(%rcx),%edx
  1b:	83 fa 02             	cmp    $0x2,%edx
  1e:	75 21                	jne    0x41
  20:	48 8b 91 18 16 00 00 	mov    0x1618(%rcx),%rdx
  27:	48 8b 32             	mov    (%rdx),%rsi
* 2a:	48 8d 7e 01          	lea    0x1(%rsi),%rdi <-- trapping instruction
  2e:	8b 89 14 16 00 00    	mov    0x1614(%rcx),%ecx
  34:	48 39 cf             	cmp    %rcx,%rdi
  37:	73 08                	jae    0x41
  39:	48 89 44 f2 08       	mov    %rax,0x8(%rdx,%rsi,8)
  3e:	48                   	rex.W
  3f:	89                   	.byte 0x89