============================= WARNING: suspicious RCU usage 5.15.175-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.1.944/7607: #0: ffff8880599f87a0 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1678 [inline] #0: ffff8880599f87a0 (sk_lock-AF_INET){+.+.}-{0:0}, at: l2tp_ip_sendmsg+0x32/0x1620 net/l2tp/l2tp_ip.c:405 #1: ffffffff8cb1fd20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311 #2: ffffffff8cb1fd20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #3: ffffffff8cb1fd80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #4: ffffffff8cb1fd80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #5: ffff88807e4f9108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #5: ffff88807e4f9108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3879 [inline] #5: ffff88807e4f9108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xc1f/0x32b0 net/core/dev.c:4221 #6: ffffffff8cb1fd20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311 stack backtrace: CPU: 1 PID: 7607 Comm: syz.1.944 Not tainted 5.15.175-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106 qdisc_lookup+0xa8/0x630 net/sched/sch_api.c:304 qdisc_tree_reduce_backlog+0x212/0x4f0 net/sched/sch_api.c:800 sfq_enqueue+0x1214/0x23e0 net/sched/sch_sfq.c:475 qdisc_enqueue include/net/sch_generic.h:832 [inline] tbf_enqueue+0x35d/0x6f0 net/sched/sch_tbf.c:243 dev_qdisc_enqueue+0x47/0x240 net/core/dev.c:3820 __dev_xmit_skb net/core/dev.c:3904 [inline] __dev_queue_xmit+0xe32/0x32b0 net/core/dev.c:4221 neigh_hh_output include/net/neighbour.h:493 [inline] neigh_output include/net/neighbour.h:507 [inline] ip_finish_output2+0xcd7/0x11a0 net/ipv4/ip_output.c:228 dst_output include/net/dst.h:443 [inline] ip_local_out net/ipv4/ip_output.c:126 [inline] __ip_queue_xmit+0x12df/0x1d90 net/ipv4/ip_output.c:532 l2tp_ip_sendmsg+0x611/0x1620 net/l2tp/l2tp_ip.c:498 sock_sendmsg_nosec net/socket.c:704 [inline] __sock_sendmsg net/socket.c:716 [inline] ____sys_sendmsg+0x59e/0x8f0 net/socket.c:2436 ___sys_sendmsg+0x252/0x2e0 net/socket.c:2490 __sys_sendmmsg+0x2bf/0x560 net/socket.c:2576 __do_sys_sendmmsg net/socket.c:2605 [inline] __se_sys_sendmmsg net/socket.c:2602 [inline] __x64_sys_sendmmsg+0x9c/0xb0 net/socket.c:2602 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 RIP: 0033:0x7f6b236ccd29 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:00007f6b2153d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00007f6b238bcfa0 RCX: 00007f6b236ccd29 RDX: 00000000040000cf RSI: 0000000020000900 RDI: 0000000000000003 RBP: 00007f6b23748aa8 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f6b238bcfa0 R15: 00007ffd8a941718