============================= 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.1.953/8405: #0: ffff88801f5d50e0 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1694 [inline] #0: ffff88801f5d50e0 (sk_lock-AF_INET){+.+.}-{0:0}, at: udp_sendmsg+0x2fb/0x2340 net/ipv4/udp.c:1104 #1: ffffffff8c11c4c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #2: ffffffff8c11c4c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #3: ffff88802ba3c108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #3: ffff88802ba3c108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3911 [inline] #3: ffff88802ba3c108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xb8a/0x2ed0 net/core/dev.c:4253 #4: ffffffff8c11c460 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311 stack backtrace: CPU: 1 PID: 8405 Comm: syz.1.953 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 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 cake_enqueue+0x1f00/0x7bb0 net/sched/sch_cake.c:1833 cbs_child_enqueue net/sched/sch_cbs.c:95 [inline] cbs_enqueue_soft+0x1a8/0x270 net/sched/sch_cbs.c:128 dev_qdisc_enqueue+0x48/0x210 net/core/dev.c:3852 __dev_xmit_skb net/core/dev.c:3936 [inline] __dev_queue_xmit+0xd7e/0x2ed0 net/core/dev.c:4253 neigh_hh_output include/net/neighbour.h:493 [inline] neigh_output include/net/neighbour.h:507 [inline] ip_finish_output2+0xc69/0x1080 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_push_pending_frames net/ipv4/udp.c:1019 [inline] udp_sendmsg+0x6c8/0x2340 net/ipv4/udp.c:1311 sock_sendmsg_nosec net/socket.c:704 [inline] __sock_sendmsg net/socket.c:716 [inline] __sys_sendto+0x423/0x580 net/socket.c:2063 __do_sys_sendto net/socket.c:2075 [inline] __se_sys_sendto net/socket.c:2071 [inline] __x64_sys_sendto+0xda/0xf0 net/socket.c:2071 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: 0033:0x7f50c600abe9 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:00007f50c4272038 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007f50c6241fa0 RCX: 00007f50c600abe9 RDX: 000000000000ffe3 RSI: 00002000000000c0 RDI: 0000000000000007 RBP: 00007f50c608de19 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f50c6242038 R14: 00007f50c6241fa0 R15: 00007ffde8f993c8