============================= WARNING: suspicious RCU usage 5.15.173-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.4.468/6252: #0: ffff0000d0ce8120 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1678 [inline] #0: ffff0000d0ce8120 (sk_lock-AF_INET6){+.+.}-{0:0}, at: mptcp_stream_connect+0x68/0x9b4 net/mptcp/protocol.c:3397 #1: ffff0000d4fb9aa0 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1678 [inline] #1: ffff0000d4fb9aa0 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: inet_stream_connect+0x5c/0xb0 net/ipv4/af_inet.c:737 #2: ffff800014c922e0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:311 #3: ffff800014c92340 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:311 #4: ffff800014c92340 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:311 #5: ffff0000e9fd3908 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #5: ffff0000e9fd3908 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3879 [inline] #5: ffff0000e9fd3908 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0x8a0/0x2ac8 net/core/dev.c:4221 #6: ffff800014c922e0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:311 stack backtrace: CPU: 1 PID: 6252 Comm: syz.4.468 Not tainted 5.15.173-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024 Call trace: dump_backtrace+0x0/0x530 arch/arm64/kernel/stacktrace.c:152 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216 __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106 dump_stack+0x1c/0x58 lib/dump_stack.c:113 lockdep_rcu_suspicious+0x188/0x1e0 kernel/locking/lockdep.c:6571 qdisc_lookup+0xc8/0x64c net/sched/sch_api.c:304 qdisc_tree_reduce_backlog+0x208/0x4a4 net/sched/sch_api.c:800 pfifo_tail_enqueue+0x280/0x38c net/sched/sch_fifo.c:51 qdisc_enqueue include/net/sch_generic.h:832 [inline] tbf_enqueue+0x2f8/0x5f0 net/sched/sch_tbf.c:237 dev_qdisc_enqueue+0x60/0x35c net/core/dev.c:3820 __dev_xmit_skb net/core/dev.c:3904 [inline] __dev_queue_xmit+0x1018/0x2ac8 net/core/dev.c:4221 dev_queue_xmit+0x24/0x34 net/core/dev.c:4289 neigh_hh_output include/net/neighbour.h:493 [inline] neigh_output include/net/neighbour.h:507 [inline] ip6_finish_output2+0x132c/0x1cec net/ipv6/ip6_output.c:130 __ip6_finish_output+0x580/0x6ec net/ipv6/ip6_output.c:201 ip6_finish_output+0x40/0x218 net/ipv6/ip6_output.c:211 NF_HOOK_COND include/linux/netfilter.h:291 [inline] ip6_output+0x274/0x594 net/ipv6/ip6_output.c:234 dst_output include/net/dst.h:443 [inline] NF_HOOK include/linux/netfilter.h:302 [inline] ip6_xmit+0x1114/0x1afc net/ipv6/ip6_output.c:338 inet6_csk_xmit+0x3b8/0x61c net/ipv6/inet6_connection_sock.c:135 __tcp_transmit_skb+0x1944/0x31e8 net/ipv4/tcp_output.c:1402 tcp_transmit_skb net/ipv4/tcp_output.c:1420 [inline] tcp_connect+0x1a94/0x3f38 net/ipv4/tcp_output.c:3891 tcp_v6_connect+0x1010/0x1878 net/ipv6/tcp_ipv6.c:337 __inet_stream_connect+0x204/0xc00 net/ipv4/af_inet.c:674 inet_stream_connect+0x74/0xb0 net/ipv4/af_inet.c:738 mptcp_stream_connect+0x648/0x9b4 net/mptcp/protocol.c:3434 __sys_connect_file net/socket.c:1923 [inline] __sys_connect+0x268/0x290 net/socket.c:1940 __do_sys_connect net/socket.c:1950 [inline] __se_sys_connect net/socket.c:1947 [inline] __arm64_sys_connect+0x7c/0x94 net/socket.c:1947 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608 el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584