============================= 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 4 locks held by syz.3.379/5912: #0: ffffffff8c31efc0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #1: ffff88805fe3c108 (&sch->q.lock){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] #1: ffff88805fe3c108 (&sch->q.lock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3924 [inline] #1: ffff88805fe3c108 (&sch->q.lock){+...}-{2:2}, at: __dev_queue_xmit+0xa2b/0x2e50 net/core/dev.c:4266 #2: ffff88805fe3c148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: packet_snd net/packet/af_packet.c:3094 [inline] #2: ffff88805fe3c148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: packet_sendmsg+0x3cf9/0x50b0 net/packet/af_packet.c:3125 #3: ffffffff8c31ef60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312 stack backtrace: CPU: 0 PID: 5912 Comm: syz.3.379 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: 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:783 cake_enqueue+0x51c1/0x8690 net/sched/sch_cake.c:1957 qdisc_enqueue include/net/sch_generic.h:842 [inline] netem_dequeue+0xd4c/0x1410 net/sched/sch_netem.c:737 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:3955 [inline] __dev_queue_xmit+0xdce/0x2e50 net/core/dev.c:4266 packet_snd net/packet/af_packet.c:3094 [inline] packet_sendmsg+0x3cf9/0x50b0 net/packet/af_packet.c:3125 sock_sendmsg_nosec net/socket.c:706 [inline] __sock_sendmsg net/socket.c:718 [inline] __sys_sendto+0x46d/0x620 net/socket.c:2073 __do_sys_sendto net/socket.c:2085 [inline] __se_sys_sendto net/socket.c:2081 [inline] __x64_sys_sendto+0xda/0xf0 net/socket.c:2081 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: 0033:0x7f7fb935d0d9 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:00007f7fb7594028 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007f7fb95e5090 RCX: 00007f7fb935d0d9 RDX: 0000000000000003 RSI: 0000200000000440 RDI: 0000000000000006 RBP: 00007f7fb93f4024 R08: 00002000000001c0 R09: 0000000000000014 R10: 0000000000000040 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f7fb95e5128 R14: 00007f7fb95e5090 R15: 00007ffc79863818