device syzkaller0 entered promiscuous mode ============================= 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.0.451/6160: #0: ffffffff8c11c7c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #1: ffffffff8c11c7c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #2: ffff88807395b108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] #2: ffff88807395b108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3911 [inline] #2: ffff88807395b108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xb8a/0x2ed0 net/core/dev.c:4253 #3: ffff88807395b148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: neigh_output include/net/neighbour.h:509 [inline] #3: ffff88807395b148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: ip_finish_output2+0xca1/0x1080 net/ipv4/ip_output.c:228 #4: ffffffff8c11c760 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312 stack backtrace: CPU: 1 PID: 6160 Comm: syz.0.451 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: dump_stack_lvl+0x168/0x230 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:793 sfq_enqueue+0x148e/0x2260 net/sched/sch_sfq.c:-1 qdisc_enqueue include/net/sch_generic.h:832 [inline] netem_dequeue+0xd39/0x1400 net/sched/sch_netem.c:737 dequeue_skb net/sched/sch_generic.c:292 [inline] qdisc_restart net/sched/sch_generic.c:397 [inline] __qdisc_run+0x237/0x1480 net/sched/sch_generic.c:415 __dev_xmit_skb net/core/dev.c:3942 [inline] __dev_queue_xmit+0xeb9/0x2ed0 net/core/dev.c:4253 neigh_output include/net/neighbour.h:509 [inline] ip_finish_output2+0xca1/0x1080 net/ipv4/ip_output.c:228 dst_output include/net/dst.h:452 [inline] ip_local_out net/ipv4/ip_output.c:126 [inline] ip_send_skb+0x129/0x1c0 net/ipv4/ip_output.c:1581 udp_send_skb+0x94a/0x1330 net/ipv4/udp.c:991 udp_sendmsg+0x1aaa/0x2340 net/ipv4/udp.c:1279 udpv6_sendmsg+0x92f/0x2320 net/ipv6/udp.c:1395 sock_sendmsg_nosec net/socket.c:706 [inline] __sock_sendmsg net/socket.c:718 [inline] ____sys_sendmsg+0x5a2/0x8c0 net/socket.c:2446 ___sys_sendmsg+0x1f0/0x260 net/socket.c:2500 __sys_sendmmsg+0x27c/0x4a0 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: 0033:0x7f42742f8749 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f427255f038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00007f427454efa0 RCX: 00007f42742f8749 RDX: 0000000000000001 RSI: 00002000000017c0 RDI: 0000000000000003 RBP: 00007f427437cf91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000008000004 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f427454f038 R14: 00007f427454efa0 R15: 00007fff76cec0b8