=============================
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
4 locks held by syz.0.67/4458:
 #0: ffffffff966b3918 (nfnl_subsys_ipset){+.+.}-{3:3}, at: call_ad+0x284/0x9a0 net/netfilter/ipset/ip_set_core.c:1748
 #1: ffffc90000007ca0 ((&q->perturb_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline]
 #1: ffffc90000007ca0 ((&q->perturb_timer)){+.-.}-{0:0}, at: call_timer_fn+0xca/0x540 kernel/time/timer.c:1638
 #2: ffff888024777908 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
 #2: ffff888024777908 (&sch->q.lock){+.-.}-{2:2}, at: sfq_perturbation+0x14d/0x2090 net/sched/sch_sfq.c:610
 #3: ffffffff8c31ef20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312

stack backtrace:
CPU: 0 PID: 4458 Comm: syz.0.67 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
Call Trace:
 <IRQ>
 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:783
 sfq_rehash net/sched/sch_sfq.c:598 [inline]
 sfq_perturbation+0x1f26/0x2090 net/sched/sch_sfq.c:613
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
 expire_timers kernel/time/timer.c:1699 [inline]
 __run_timers+0x56c/0x810 kernel/time/timer.c:1970
 handle_softirqs+0x336/0x830 kernel/softirq.c:576
 do_softirq+0x142/0x210 kernel/softirq.c:477
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x180/0x1c0 kernel/softirq.c:401
 spin_unlock_bh include/linux/spinlock.h:409 [inline]
 hash_netportnet6_add+0x2b13/0x3750 net/netfilter/ipset/ip_set_hash_gen.h:983
 hash_netportnet6_uadt+0xbbc/0xf60 net/netfilter/ipset/ip_set_hash_netportnet.c:560
 call_ad+0x387/0x9a0 net/netfilter/ipset/ip_set_core.c:1753
 ip_set_ad+0x816/0x9c0 net/netfilter/ipset/ip_set_core.c:1841
 nfnetlink_rcv_msg+0xbf7/0x1180 net/netfilter/nfnetlink.c:297
 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2512
 nfnetlink_rcv+0x2b4/0x2450 net/netfilter/nfnetlink.c:654
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x78f/0x940 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1923
 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: 0033:0x7f6623412e99
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:00007f662166b028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f662369afa0 RCX: 00007f6623412e99
RDX: 0000000000000000 RSI: 00002000000002c0 RDI: 0000000000000004
RBP: 00007f66234a8eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f662369b038 R14: 00007f662369afa0 R15: 00007ffd1b75bc18
 </TASK>