============================= WARNING: suspicious RCU usage 5.15.189-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.2.125/4703: #0: ffff888078c99c20 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1694 [inline] #0: ffff888078c99c20 (sk_lock-AF_INET6){+.+.}-{0:0}, at: sctp_sendmsg+0xa7c/0x2950 net/sctp/socket.c:1971 #1: ffffffff8c11c360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311 #2: ffffffff8c11c3c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #3: ffffffff8c11c3c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #4: ffff88805fd05108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #4: ffff88805fd05108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3911 [inline] #4: ffff88805fd05108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xb8a/0x2ed0 net/core/dev.c:4253 #5: ffffffff8c11c360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311 stack backtrace: CPU: 0 PID: 4703 Comm: syz.2.125 Not tainted 5.15.189-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+0x1f94/0x7ee0 net/sched/sch_cake.c:1832 qdisc_enqueue include/net/sch_generic.h:832 [inline] tbf_enqueue+0x224/0x6e0 net/sched/sch_tbf.c:243 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] ip6_finish_output2+0x1035/0x1500 net/ipv6/ip6_output.c:130 dst_output include/net/dst.h:452 [inline] NF_HOOK include/linux/netfilter.h:302 [inline] ip6_xmit+0x1054/0x1670 net/ipv6/ip6_output.c:338 sctp_v6_xmit+0x980/0x1190 net/sctp/ipv6.c:250 sctp_packet_transmit+0x239f/0x2920 net/sctp/output.c:652 sctp_outq_flush_transports net/sctp/outqueue.c:1170 [inline] sctp_outq_flush+0xe45/0x30d0 net/sctp/outqueue.c:1218 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:-1 [inline] sctp_side_effects net/sctp/sm_sideeffect.c:1199 [inline] sctp_do_sm+0x4e61/0x5500 net/sctp/sm_sideeffect.c:1170 sctp_assoc_bh_rcv+0x3ee/0x630 net/sctp/associola.c:1054 sctp_backlog_rcv+0x15f/0x3c0 net/sctp/input.c:346 sk_backlog_rcv include/net/sock.h:1061 [inline] __release_sock+0x1b9/0x420 net/core/sock.c:2725 release_sock+0x5b/0x1b0 net/core/sock.c:3266 sctp_sendmsg+0x1bf0/0x2950 net/sctp/socket.c:2037 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: 0033:0x7fd09ab56be9 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:00007fd098d9d038 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007fd09ad7e090 RCX: 00007fd09ab56be9 RDX: 0000000000034000 RSI: 0000200000847fff RDI: 0000000000000003 RBP: 00007fd09abd9e19 R08: 000020000005ffe4 R09: 000000000000001c R10: 00000000000000e0 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fd09ad7e128 R14: 00007fd09ad7e090 R15: 00007fff8b6a6b88