============================= 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 7 locks held by syz.5.628/7234: #0: ffff8880778fc920 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1744 [inline] #0: ffff8880778fc920 (sk_lock-AF_INET){+.+.}-{0:0}, at: tcp_sendmsg+0x1d/0x40 net/ipv4/tcp.c:1459 #1: ffffffff8d11efa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #2: ffffffff8d11efa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #3: ffffffff8d11f000 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #4: ffffffff8d11f000 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #5: ffff888079ef9108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] #5: ffff888079ef9108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3925 [inline] #5: ffff888079ef9108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xa2b/0x2e50 net/core/dev.c:4267 #6: ffffffff8d11efa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312 stack backtrace: CPU: 0 PID: 7234 Comm: syz.5.628 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026 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:800 cake_enqueue+0x20ab/0x8270 net/sched/sch_cake.c:1828 qdisc_enqueue include/net/sch_generic.h:844 [inline] tbf_enqueue+0x225/0x6e0 net/sched/sch_tbf.c:243 dev_qdisc_enqueue+0x48/0x210 net/core/dev.c:3866 __dev_xmit_skb net/core/dev.c:3950 [inline] __dev_queue_xmit+0xbde/0x2e50 net/core/dev.c:4267 neigh_hh_output include/net/neighbour.h:493 [inline] neigh_output include/net/neighbour.h:507 [inline] ip_finish_output2+0xc77/0x10e0 net/ipv4/ip_output.c:228 NF_HOOK_COND include/linux/netfilter.h:291 [inline] ip_output+0x2ba/0x3e0 net/ipv4/ip_output.c:434 dst_output include/net/dst.h:452 [inline] ip_local_out net/ipv4/ip_output.c:126 [inline] __ip_queue_xmit+0x11fc/0x1c60 net/ipv4/ip_output.c:538 __tcp_transmit_skb+0x1ca3/0x31e0 net/ipv4/tcp_output.c:1404 tcp_transmit_skb net/ipv4/tcp_output.c:1422 [inline] tcp_write_xmit+0x1a8d/0x65c0 net/ipv4/tcp_output.c:2718 tcp_sendmsg_locked+0x1ebd/0x3330 net/ipv4/tcp.c:1413 tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1460 sock_sendmsg_nosec net/socket.c:706 [inline] __sock_sendmsg net/socket.c:718 [inline] ____sys_sendmsg+0x5be/0x8f0 net/socket.c:2446 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2500 __sys_sendmsg net/socket.c:2529 [inline] __do_sys_sendmsg net/socket.c:2538 [inline] __se_sys_sendmsg+0x1b7/0x2a0 net/socket.c:2536 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: 0033:0x7fa169f7db19 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:00007fa1681d4028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007fa16a203fa0 RCX: 00007fa169f7db19 RDX: 0000000000000000 RSI: 00002000000004c0 RDI: 0000000000000003 RBP: 00007fa16a015b70 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fa16a204038 R14: 00007fa16a203fa0 R15: 00007ffc107550c8