============================= WARNING: suspicious RCU usage 5.15.185-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.1.617/6488: #0: ffff888029d52520 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1694 [inline] #0: ffff888029d52520 (sk_lock-AF_INET){+.+.}-{0:0}, at: tcp_sendmsg+0x1d/0x40 net/ipv4/tcp.c:1456 #1: ffffffff8c11bfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #2: ffffffff8c11c000 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #3: ffffffff8c11c000 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #4: ffff888022b14108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #4: ffff888022b14108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3911 [inline] #4: ffff888022b14108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xb8a/0x2ed0 net/core/dev.c:4253 #5: ffffffff8c11bfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311 stack backtrace: CPU: 1 PID: 6488 Comm: syz.1.617 Not tainted 5.15.185-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 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+0x213/0x4e0 net/sched/sch_api.c:800 cake_enqueue+0x1f94/0x7ee0 net/sched/sch_cake.c:1832 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_queue_xmit+0x11c3/0x1c00 net/ipv4/ip_output.c:532 __tcp_transmit_skb+0x1d2a/0x3410 net/ipv4/tcp_output.c:1404 tcp_transmit_skb net/ipv4/tcp_output.c:1422 [inline] tcp_write_xmit+0x1907/0x6590 net/ipv4/tcp_output.c:2707 tcp_sendmsg_locked+0x1c06/0x3590 net/ipv4/tcp.c:1410 tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1457 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: 0033:0x7f6b477d8929 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:00007f6b45640038 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007f6b479fffa0 RCX: 00007f6b477d8929 RDX: ffffffffffffff94 RSI: 0000200000000000 RDI: 0000000000000003 RBP: 00007f6b4785ab39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f6b479fffa0 R15: 00007ffcffdeebd8