============================= 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 5 locks held by syz.2.330/5494: #0: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #1: ffffffff8c31eb00 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #2: ffffffff8c31eb00 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #3: ffff888144d1f108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] #3: ffff888144d1f108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3911 [inline] #3: ffff888144d1f108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xa2a/0x2fd0 net/core/dev.c:4253 #4: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312 stack backtrace: CPU: 0 PID: 5494 Comm: syz.2.330 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 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 sfq_enqueue+0x14ad/0x2280 net/sched/sch_sfq.c:-1 qdisc_enqueue include/net/sch_generic.h:832 [inline] tbf_enqueue+0x224/0x6e0 net/sched/sch_tbf.c:243 dev_qdisc_enqueue+0x48/0x210 net/core/dev.c:3852 __dev_xmit_skb net/core/dev.c:3936 [inline] __dev_queue_xmit+0xc25/0x2fd0 net/core/dev.c:4253 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 ip6_send_skb+0x1b9/0x360 net/ipv6/ip6_output.c:1952 udp_v6_send_skb+0xa28/0x1680 net/ipv6/udp.c:1285 udpv6_sendmsg+0x1e11/0x2650 net/ipv6/udp.c:1586 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: 0033:0x7f482fd86cb9 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:00007f482dfa0028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00007f4830002180 RCX: 00007f482fd86cb9 RDX: 00000000000004ff RSI: 00002000000092c0 RDI: 0000000000000005 RBP: 00007f482fdf4bf7 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f4830002218 R14: 00007f4830002180 R15: 00007ffcf600ce98